CLASS: VII SUBJECT: SCIENCE TOPIC: Life Processes in Plants

LIFE PROCESS

Gas Exchange
Nutrition Growth Transport Respiration
(Stomata)

Photosynthesis Break down of food

Leaves (Food Release of energy

Factories)
Xylem (Water,
Sunlight Minerals)

Phloem (Food)
CO₂

Water

Terms & Definitions

• Photosynthesis: The process by which green plants prepare their food using sunlight,
carbon dioxide, water, and chlorophyll.
• Chlorophyll: A green pigment in leaves that absorbs sunlight for photosynthesis.
• Stomata: Tiny pores on the surface of leaves that help in the exchange of gases.
• Xylem: Vascular tissue in plants that transports water and minerals from roots to
leaves.
• Phloem: Vascular tissue that transports food (glucose) from leaves to other parts of the
plant.
1.•Growth
Respiration: The process of breaking down glucose using oxygen to release energy,
in Plants
carbon dioxide, and water

1. Growth in Plants

• Plants grow by producing new leaves, flowers, branches, and increasing in height and
girth.
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 • Growth is influenced by:
o Water – essential for transporting nutrients and photosynthesis.
o Sunlight – provides energy for making food.
o Air (carbon dioxide) – taken in from the atmosphere for food synthesis.
• Plants that receive both water and sunlight show healthy growth. Lack of either one
affects growth.

2. How Plants Get Their Food

• Leaves – The Food Factories

o Green leaves prepare food through a process called photosynthesis.

o The green pigment chlorophyll in leaves captures sunlight, enabling the plant
to make food.
o The food produced is a simple sugar called glucose, which is later converted
into starch for storage.
• Essentials for
Photosynthesis: Plants need
the following to carry out
photosynthesis:

o Sunlight – source of
energy
o Chlorophyll – absorbs
sunlight
o Carbon dioxide – taken
in from air
o Water – absorbed from
soil
3. Role of Leaf Colour in Photosynthesis

• Green parts of leaves contain chlorophyll and can perform photosynthesis.

• Non-green patches (e.g., white, red) may not contain chlorophyll and may not
produce starch.
• Some leaves appear red or violet due to other pigments, but may still contain
chlorophyll beneath, allowing photosynthesis.

4. Gas Exchange in Leaves

• Stomata are tiny pores mostly on the underside of leaves.

• They help in the exchange of gases — taking in carbon dioxide and releasing oxygen
during photosynthesis.
• During respiration, they allow oxygen in and carbon dioxide out.
5. Transport in Plants

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 • Transport of Water and Minerals

o Water and minerals are absorbed from the soil by roots.

o They are transported upward to all parts of the plant through xylem – a network
of tube-like structures.

• Transport of Food

• Food made in leaves is distributed to other parts of the plant through phloem –
another set of tube-like tissues.
• This process ensures all plant parts get energy and nutrients.
• Food prepared in the leaves is transported through phloem to:
o Growing parts
o Storage organs (e.g., roots, seeds, fruits)

6. Respiration in Plants

• Like all living beings, plants also respire.

• They break down glucose in the presence of oxygen to release energy, carbon
dioxide, and water.
• Word Equation for Respiration:

Glucose + Oxygen → Carbon dioxide + Water + Energy

• This energy is used by the plant for growth, repair, and functioning.
• Respiration happens in all parts of a plant – both green and non-green.

SUMMARY OF KEY PROCESSES

Process Inputs Outputs Main Site
Photosynthesis CO₂, Water, Sunlight, Glucose, Oxygen Leaves (green
Chlorophyll parts)
Respiration Glucose, Oxygen CO₂, Water, Energy All plant parts
Water Water, Minerals Delivered to all parts Xylem tissues
Transport
Food Transport Glucose (from leaves) Delivered to other Phloem tissues
parts
Gas Exchange CO₂ and O₂ In and out through Leaf surface
stomata

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 Did You Know?

1. Rustom Hormusji Dastur studied the effects of water, temperature, and light colour
on photosynthesis.

2. Kamala Sohonie, the first Indian woman to earn a PhD in science, researched plant
respiration and nutrition.

Important Concepts to Remember

• Leaves are green due to chlorophyll and are the main sites of
food production.
• Without sunlight or carbon dioxide, photosynthesis cannot take
place.
• Plants do not "eat" food — they make their own through
photosynthesis.
• Oxygen is released only when all conditions of photosynthesis are
met.
• Even non-green plants respire and transport substances..

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ACTIVITY FILE:
ACTIVITY 1
Aim: To prove that sunlight is essential for the process of photosynthesis.
Materials Required: Two potted plants, aluminium foil or black paper, paper clips or tape, iodine solution,
alcohol, water, beaker, test tube, burner or hot water bath, forceps, dropper.
Procedure:
1. Keep one plant in sunlight and another in complete darkness for about 36 hours to destarch them.
2. On the plant kept in sunlight, cover part of one leaf with aluminium foil or black paper using paper clips
or tape.
3. After a few hours, pluck the covered leaf from the plant.
4. Boil the leaf in water for 2–3 minutes to soften it.
5. Transfer the leaf to a test tube containing alcohol and place the test tube in a beaker of hot water until
the leaf becomes decolourised.
6. Rinse the leaf in warm water and place it on a white tile.
7. Add a few drops of iodine solution on the leaf and observe.
Observation: The uncovered (exposed) green part of the leaf turns blue-black, while the covered part does
not show any colour change.
Conclusion: Only the parts of the leaf that received sunlight could perform photosynthesis and produce
starch. Hence, sunlight is necessary for photosynthesis.
Precautions:
Use alcohol carefully, away from direct flame as it is highly flammable.

Handle hot liquids and glassware with care to avoid burns or breakage.
Ensure the leaf is fully decolourised before adding iodine for clear results

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ACTIVITY2
Aim: To observe stomata (tiny pores) on the surface of a leaf using a microscope.
Materials Required: Fresh leaf (rhoeo, money plant, hibiscus, or onion), watch glass, water, microscope slide,
coverslip, dropper, forceps, needle, microscope, ink or safranin.

Procedure:
1. Take a fresh leaf and tear it gently to peel a thin transparent layer from the lower surface.
2. Place the peel in a watch glass containing water to prevent it from drying.
3. Using forceps, transfer the peel onto a clean microscope slide.
4. Add a drop of water (or stain like diluted ink or safranin) on the peel.
5. Gently place a coverslip over the peel to avoid air bubbles.
6. Observe the slide under the microscope under low and then high magnification.
Observation: Small pores surrounded by bean-shaped cells are visible on the peel surface.
Conclusion: These pores are stomata, and the bean-shaped cells are guard cells. Stomata regulate gas
exchange and water loss in plants.
Precautions:
1. Handle the leaf peel gently to avoid tearing.
2. Use stain sparingly for better visibility.
3. Ensure the coverslip is placed carefully to avoid trapping air bubbles.
4. Adjust the microscope focus slowly to avoid damaging the slide.

(i) (ii)

Fig: Diagrams for Activity File

(i) Apparatus for activity 1

(ii) Stomata

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 ASSIGNMENT
I MCQ
1. Which two things are most essential for healthy plant growth?
(a) Soil and shade (b) Water and sunlight (c) Air and insects (d) Roots and stems
2. Which of the following is NOT an essential requirement for photosynthesis?
(a) Sunlight (b) Water (c) Oxygen (d) Chlorophyll
3. Where does photosynthesis primarily occur in plants?
(a) Roots (b) Flowers (c) Leaves (d) Stem
4. What is the main food produced by plants during photosynthesis?
(a) Starch (b) Glucose (c) Oxygen (d) Water
5. What is the function of stomata in leaves?
(a) To absorb water (b) To release oxygen (c) To facilitate gas exchange (d)
To make food
6. Which of the following is transported through the phloem in plants?
(a) Water (b) Minerals (c) Glucose (d) Oxygen
7. Which part of the plant is responsible for absorbing water and minerals from the
soil?
(a) Leaves (b) Flowers (c) Roots (d) Stem
8. During respiration, plants release:
(a) Oxygen and energy (b) Carbon dioxide and water
(c) Water and glucose (d) Carbon dioxide and energy
9. Which gas is essential for photosynthesis?
(a) Oxygen (b) Nitrogen (c) Carbon dioxide (d) Hydrogen
10. What is the main pigment in leaves that helps absorb sunlight for photosynthesis?
(a) Carotene (b) Chlorophyll (c) Anthocyanin (d) Xanthophyll
11. Which process occurs in all parts of a plant, both green and non-green?
(a) Photosynthesis (b) Respiration (c) Transpiration (d) Germination
12. What happens to the glucose produced in photosynthesis?
(a) It is immediately converted into oxygen. (b) It is stored as starch or used for
energy.
(c) It is expelled through stomata. (d) It is absorbed by the roots.
13. What is the main function of xylem in plants?
(a) Transport of water and minerals (b) Transport of glucose
(c) Photosynthesis (d) Gas exchange
14. What happens if a plant does not receive enough sunlight?
(a) It will stop breathing. (b) It will not be able to make food.
(c) It will lose all its leaves. (d) It will grow taller.
15. Which of the following scientists studied the effects of light on photosynthesis?
(a) Kamala Sohonie (b) Rustom Hormusji Dastur (c) Charles Darwin (d) Albert
Einstein

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II VERY SHORT ANSWER TYPE QUESTION

1. Explain the role of chlorophyll in photosynthesis.

2. Why is carbon dioxide essential for the process of photosynthesis?
3. Describe how plants transport water from the roots to the leaves.
4. What happens to the glucose produced during photosynthesis in plants?
5. How do stomata facilitate gas exchange in leaves?
6. What is the main difference between the transport of food and the transport of
water in plants?
7. Why do non-green parts of the plant, such as red or white leaves, not perform
photosynthesis efficiently?
8. What is the significance of respiration in plants? How does it differ from
photosynthesis?
9. Name the two processes that occur in plant cells that require oxygen.
10. How do plants benefit from transpiration?

III SHORT ANWER TYPE QUESTIONS

1. Explain the process of photosynthesis, including all the inputs and outputs, and the
role of chloroplasts.
2. Discuss the role of xylem and phloem in the transport of substances within the plant.
How are their structures suited to their functions?
3. Why is water considered a crucial factor in both photosynthesis and plant growth?
Provide examples of its importance.
4. Explain the interdependence between respiration and photosynthesis in plants. How
do these processes complement each other?
5. How do environmental factors like temperature and light intensity affect the rate of
photosynthesis in plants?

IV SHORT ANWER TYPE QUESTIONS

1. Analyze the process of photosynthesis in plants, highlighting the importance of each

component involved, including sunlight, chlorophyll, carbon dioxide, and water. How
do these factors interact to produce glucose and oxygen?
2. Examine the role of stomata in the overall functioning of plants. Discuss how stomata
contribute to processes such as gas exchange, transpiration, and the regulation of
water loss. What factors affect the opening and closing of stomata?
3. Discuss the significance of water and mineral transport in plants. How does the xylem
ensure the movement of water and nutrients from the roots to the leaves, and how
is this process critical for photosynthesis and plant survival?
4. Compare and contrast the processes of respiration and photosynthesis in plants.
Analyze how these two processes are complementary, and explain how plants
maintain a balance between them to ensure optimal growth and energy production.
5. Evaluate the effect of environmental conditions such as light intensity, temperature,
and carbon dioxide concentration on the rate of photosynthesis in plants. How do
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 these factors influence plant growth, and what adaptations do plants have to survive
in varying conditions?

V HIGH ORDER THINKING SKILL QUESTION

1. A gardener noticed that a few plants in his garden were not growing as expected.
Despite receiving plenty of water and sunlight, the plants were not producing enough
leaves and flowers. He observed that these plants had weak stems, and the leaves
appeared to be turning yellow. Upon checking, the gardener found that the plants
had an abundance of carbon dioxide but lacked sufficient water.

Question: Analyze the situation and explain how the lack of water could be affecting
the plants’ growth and photosynthesis. Why is water crucial for the plant’s health,
and what steps should the gardener take to improve the situation?

Hint for Answer:

• Water is essential for photosynthesis as it is one of the key inputs needed to produce
glucose.
• Without enough water, the plants cannot perform photosynthesis efficiently, leading
to poor growth and yellowing of leaves (chlorosis).
• Water also helps transport nutrients through the plant, so without it, the plant will
not be able to absorb and circulate necessary minerals.
• Solution: The gardener should increase water supply and ensure the plants receive
adequate hydration, which will support photosynthesis and overall growth.

2. In a classroom experiment, students placed two plants in different conditions to

study their growth. One plant was placed in a sunny spot, and the other was kept in a
shaded area with limited sunlight. After a few days, the plant in the sunny spot was
growing taller and producing more leaves, while the plant in the shaded area showed
slower growth and fewer leaves.

Question: Evaluate the impact of sunlight on the growth of the plants. Explain how
the plant in the sunny spot was able to perform photosynthesis more effectively than
the one in the shade. What conclusions can be drawn about the role of sunlight in
plant growth?

Hint for Answer:

• Sunlight is crucial for photosynthesis as it provides the energy needed to convert

carbon dioxide and water into glucose.
• The plant in the sunny spot received more energy for photosynthesis, allowing it
to produce more glucose, which is used for growth.
• The plant in the shaded area had less access to sunlight, limiting its ability to
make food and thus slowing its growth.

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3. A teacher demonstrated the process of gas exchange in plants by using a potted
plant. The plant was placed in a sealed glass container, and the students observed
that the plant was taking in carbon dioxide and releasing oxygen during the day when
exposed to light. However, at night, the plant was releasing carbon dioxide and taking
in oxygen.

Question: Discuss the process of gas exchange in plants and explain the different
roles of carbon dioxide and oxygen during the day and night. How does this support
the plant's growth and respiration?

Hint for Answer:

• During the day, plants take in carbon dioxide and release oxygen through stomata
as part of photosynthesis, which helps them produce glucose and grow.
• At night, when there is no sunlight, plants cannot perform photosynthesis, so
they switch to respiration, where they take in oxygen and release carbon dioxide
as they break down glucose for energy.
• This exchange of gases is essential for both the plant’s growth (through
photosynthesis) and its energy needs (through respiration).

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CLASS: VII SUBJECT: SCIENCE TOPIC: ACIDS, BASES AND SALTS

Key Concepts for Acid Bases and Salt

Organic Acid: - Acids that occur naturally in plant and animal materials.

Substance/Compound

Acid Base Salt

Natural
Mineral acids Occurimg
weak Base Strong Base
e.g.sulphuric Acids/Organic
acid e.g.Potassium
acid,Hydrochl e.g.Ammonium
oric acid etc.
hydroxide
e.g.citric hydroxide
acid,oxalic acid
etc. Neutral Acidic Basic

NaOH+HCl NaCl+H2O

Mineral acid-: The acids prepared from minerals of earth.

Neutral Substances: - Substances which are neither acidic nor basic in nature.
Indicators: - Those substances which are used to test whether a substance is acidic or basic
by showing change in colour in acidic and basic solution.
Neutralization reaction: - The reaction between an acid and a base to produce salt, water
and heat.
Acids, bases and salts are the three important groups of chemical compounds which are
useful to us in many ways. For example, our stomach makes an acid (Hydrochloric acid)
which is necessary for the digestion of food; baking soda (Sodium bicarbonate) used in
baking bread is a base; whereas common salt (sodium chloride) used in cooking food is a
salt. Some of the acids, bases and salts occur in nature whereas many acids, bases and salts
are made artificially in factories.
ACIDS –Acids are substances which are,
• sour in taste and turn blue litmus paper red.
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 • corrosive in nature
Eg: Lemon juice, Orange juice, Vinegar, Curd, Tamarind, Amla, Grapes
CLASSIFICATION OF ACIDS
Logo on bottle containing acid
Acids can be classified in the following categories on the basis of its occurrence:
(A) Organic acids: - These are the naturally occurring acids. They are found in various types
of plants, minerals and animals.
• These acids are weak acids.
• Many of our food items contain such weak acids in varying amounts.
Eg: – Oxalic acid, Acetic acid, Formic acid, Citric acid, lactic acid, Tartaric, Ascorbic
etc.
(B) Mineral acids –
• Sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) are some
commonly used mineral acids.
• These acids are strong acids.
• Most of them are corrosive and causes skin burns.
• One of the mineral acids, hydrochloric acid (HCl) is present in our stomach that
helps in the digestion of food.

TEST FOR ACIDS:

INDICATORS: Substances which are used to test whether a substance is acidic or basic by
showing change in colour in acidic and basic solution are called indicators. Eg: Turmeric,
litmus, china-rose petals are some naturally occurring indicators, whereas methyl orange
and phenolphthalein are man-made indicators.
Types of Indicators: Indicators can be divided into two types:
Natural Indicator: Indicators that are obtained from naturally occurring substances are
called natural indicators. For example; litmus, turmeric, China rose extract, red rose extract
etc.
Synthetic Indicator: Indicators that are made in laboratory are called synthetic indicators.
For example, phenolphthalein, methyl orange, etc.
Olfactory Indicators: Substances whose odours change in an acidic or basic medium.
Example: Onion, clove, vanilla essence etc.

INDICATORS COLOUR IN ACIDIC MEDIUM

BLUE LITMUS SOLUTION RED
TURMERIC POWDER SOLUTION YELLOW
CHINA ROSE SOLUTION DARK PINK ( MAGENTA)

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PHENOLPHTHALEIN COLOURLESS
METHYL ORANGE RED
RED ROSE EXTRACT RED

Uses of acids –
(a) Acetic acid and citric acid are used as food preservatives. These acids also provide
flavour to the food.
(b) The use of Sulphuric acid is so large ( in lead storage batteries, manufacture of drugs,
detergents, paints, fertilizers and many salts like CuSO 4, MgSO4 etc.) and so important
that it is known as King of Acids.
(c) Nitric acid is used in the manufacture of fertilizers. Nitric acid is used in manufacture of
explosives such as nitroglycerine.
(d) Hydrochloric acid is used as a bathroom cleaner.

Fact File
Nitro-glycerine has medical use also. It acts as vasodilator (a chemical
which widens blood vessels), so it is useful in diseases related to
circulation and the heart.
It is also anti-venom to the bite of the brown recluse spider.

BASES
Bases are substances which are,
• Soapy in touch and turn red litmus paper blue.
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 • Generally bitter in taste, but everything that tastes bitter may not contain a base. For
example, bitter gourd (karela) possesses a bitter taste but is not basic in nature.
Example: toothpaste, lime (Chuna, Whitewash), washing soap, caustic soda (NaOH),
caustic potash (KOH) etc.
• Lime water: It can be easily prepared by mixing lime in water and leaving it
undisturbed for some time, say an hour. Filter the liquid into another container and
use it as lime water.

TEST FOR BASES:

INDICATORS COLOUR IN BASIC MEDIUM

RED LITMUS SOLUTION BLUE
TURMERIC POWDER SOLUTION RED
CHINA ROSE SOLUTION GREEN
PHENOLPHTHALEIN PINK
METHYL ORANGE YELLOW
RED ROSE EXTRACT GREEN

Uses of bases –
(a) Lime (CaO) and slaked lime [Ca (OH)2] are used in white washing, in neutralizing
acidic soils and in the manufacture of tooth pastes (in order to neutralize the acid
produced in the teeth by bacterial action).
(b) Magnesium hydroxide (milk of magnesia) is used to neutralize the acidity of stomach;
hence it helps in relieving stomach ache.
(c) Sodium hydroxide (caustic soda) is used in the manufacture of soaps.

SALTS– When an acid reacts with a base, a new substance is formed known as
salt. It can be acidic, basic or neutral. E.g. Common salt (Sodium chloride),
Potassium chloride, Calcium carbonate etc.

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NEUTRAL SOLUTION – Those solutions which do not change the colour of either red or blue
litmus (or any other indicator) is called neutral solution. Eg: Sugar solution, Distilled water,
Salt solution etc. They are neither acidic nor basic.
NEUTRALISATION– The reaction between an acid and a base to produce salt and water with
the evolution or release of heat is called neutralization reaction.
Eg. HCl + NaOH → NaCl + H2O + Heat
(Acid)(Base) (Salt) (Water)
Neutralization in everyday life
1. Indigestion – Excessive secretion of Hydrochloric acid in the stomach leads to
indigestion. The presence of excess of acid causes damage to the walls of the stomach
resulting in ulcers (wounds). We take milk of magnesia [(Mg (OH) 2] which neutralizes
the effect of excess acid in the stomach and relieves pain in the stomach.
2. Ant sting – The sting of an ant contains formic acid. So, in case of ant bite, we rub soap
solution or moist baking soda or calamine lotion (ZnCO 3) which neutralizes the effect of
ant sting and relieves the pain.
3. Soil Treatment – Plants do not grow well in too acidic or too basic soil. Therefore, to
neutralize too acidic soil, slaked lime or quick lime is added which are basic in nature.
Similarly, too basic soils are treated with organic matters which release acids to
neutralize the soil.
Sometimes, the soil may be neutral, but the plants growing in it may still show poor
health, which can be due to the deficiency of nutrients in the soil.
4. Factory wastes – The wastes of many factories contain acid. If they are
allowed to flow into water bodies, the acids will kill fish and other aquatic
plants and organisms. Therefore, they are neutralized by adding basic
substances before releasing into the lake.
If we dissolve a large quantity of a substance in a small quantity of water, we get a
concentrated solution but if a small quantity of substance is dissolved in a large quantity of
water, we get a dilute solution. The concentration of an acid is an indicator of the amount
of water it contains. Mineral acid which has less water content are called concentrated acid
and having more water content are called dilute acids. To dilute the acid, add acid to water
and not water to the acid.
Acid rain: Acid rain, precipitation possessing a pH of about 5.2 or below primarily produced
from the emission of sulphur dioxide (SO2) and nitrogen oxides (NOx; the combination of
NO and NO2) from human activities, mostly the combustion of fossil fuels. In acid-sensitive
landscapes, acid deposition can reduce the pH of surface waters and lower biodiversity. It
weakens trees and increases their susceptibility to damage from other stressors, such
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as drought, extreme cold, and pests. In acid-sensitive areas, acid rain also depletes soil of
important plant nutrients and buffers, such as calcium and magnesium, and can
release aluminium, bound to soil particles and rock, in its toxic dissolved form. Acid rain
contributes to the corrosion of surfaces exposed to air pollution and is responsible for the
deterioration of limestone and marble buildings and monuments.
The phrase acid rain was first used in 1852 by Scottish chemist Robert Angus Smith during
his investigation of rainwater chemistry near industrial cities in England and Scotland. The
phenomenon became an important part of his book Air and Rain: The Beginnings of a
Chemical Climatology (1872). It was not until the late 1960s and early 1970s, however, that
acid rain was recognized as a regional environmental issue affecting large areas of
western Europe and eastern North America. Acid rain also occurs in Asia and parts
of Africa, South America, and Australia.
ACTIVITY:
Create a beautiful secret card for your Friends Birthday, by writing the birthday wish using
Baking powder/ Lemon juice. Ask your fiend to use Indicators like Turmeric/ China Rose
extract/ red rose extract to reveal the secret wish.
OR
Write a Poem/ Song on Acids and Bases.
Example:
Acids taste sour, Even turmeric and china rose
And bases taste bitter,
But don’t try to taste, When we mix bases and acids,
Unless you want blisters. They affect each other,
They neutralise each other
Lactic acid is in curd And don’t even bother.
And acetic acid in vinegar
Oxalic acid is in spinach,
And citric acid in citrus fruits.

Bases end with “Hydroxide”

Learn this side by side.
Potassium Hydroxide is in soap,
And Ammonium Hydroxide in window
cleaner.

When you add an indicator,

Acid or bases change colours,’
Litmus is the famous of them all,
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Activity I (To be written in Activity File)
ACTIVITY
Aim: To prepare natural indicators like turmeric paper and red rose extract.
Materials Required: Turmeric powder, water, thick sheet of paper, red rose flower (petals),
warm water.
Procedure: a) Turmeric Paper
1. Make turmeric paste by mixing turmeric in water.
2. Apply the paste on a sheet.
3. Let the sheet get dry in sunlight.
4. Cut the strips of the sheet and use to test the solutions.
5. Test various samples of acids and bases.

b) Red Rose Solution

1. Take the petals of red rose flowers.
2. Put rose petals in warm water.
3. Keep the mixture undisturbed till water becomes coloured.
4. Filter the water from the mixture and your indicator is ready to use.
5. Test various samples of acids and bases.
Observation: 1. Turmeric paper turns dark red in basic substances whereas it remains yellow in
acidic substances.
2. Red rose extract changes to green in basic solution and red in acidic solution.
Activity II (To be written in Activity File)
AIM: To study the effect of indicators on various samples of solutions.
Take various samples of solutions and tell whether substance is acidic, basic or neutral after
testing with various indicators. Fill information in the table given below:
Solution/Sample Colour change Colour change Colour Colour Acid/base/
with with change Change
Neutral
phenolphthalein with with
Blue Red
Red turmeric
litmus Litmus
Rose paper
paper paper
extract
Lemon juice
Ammonium

SCM VII 2025-26 TERM- 1 Page 17 of 12

hydroxide

Dilute
Hydrochloric acid

Common salt
solution
Washing soda
solution
Lime juice
Distilled water
NaCl solution
Soap solution
Amla juice
Tap water

ASSIGNMENT
1. ‘Litmus’, a natural dye is an extract of which of the following?
(a) China rose (b) Beetroot (c) Lichen (d) Blue berries
2. Bases taste
(a) Sweet (b) salty (c) sour (d) bitter
3. Which of the following is a strong acid?
(a) Acetic acid (b) Citric acid (c) Sulphuric acid (d) Lactic acid
4. Milk of magnesia is used in case of:
(a) cleaning toilet (b) indigestion (c) ant sting (d) bee sting
5. Tomato is sour in taste because it has
(a) Acetic acid (b) Ascorbic acid (c) oxalic acid (d) Lactic acid
6. Which acid is present in vinegar?
(a) Acetic acid (b) Ascorbic acid (c) oxalic acid (d) Lactic acid
7. Which base is used in white washing?
SCM VII 2025-26 TERM- 1 Page 18 of 12
 (a) Calcium hydroxide (b) Magnesium hydroxide
(c) Ammonium hydroxide (d) Sodium hydroxide
8. Which base is used to prepare soap?
(a) Sodium hydroxide (b) Magnesium hydroxide
(c) Calcium hydroxide (d) Ammonium hydroxide
9. When an ant stings a person, it causes a burning pain. Which of the following should
be rubbed on the stung area of the skin to get relief?
(a) Lemon juice (b) Baking soda solution
(c) Vinegar solution (d) Formic acid solution
10. Which of the following is a neutral solution?
(a) Sugar solution (b) Sulphuric acid
(c) Sodium hydroxide (d) Vinegar
11. Which of the following set of substances contain acids?
(a) Grapes, lime water (b) Vinegar, soap
(c) Curd, milk of magnesia (d) Curd, vinegar
12. What will be the colour of phenolphthalein in vinegar?
(a) Yellow (b) orange (c) red (d) colourless
13. Chemically “Milk of magnesia” is
(a) Sulphuric acid (b) nitric acid
(c) Sodium hydroxide (d) magnesium hydroxide
14. Which acid is found in our stomach?
(a) Sulphuric acid (b) Hydrochloric acid
(c) Nitric acid (d) Magnesium carbonate
15. The following observations were made by students A, B, C and D when they rubbed
soap solution on dry litmus paper:
Student Effect on dry red litmus Effect on dry blue litmus paper
paper
A Colour changed to blue No change
B No change Colour changed to red

SCM VII 2025-26 TERM- 1 Page 19 of 12

 C Colour changed to blue Colour changed to red
D No change No change
The correct observation was made by the student
(a) A (b) B (c) C (d) D
VERY SHORT ANSWER QUESTIONS
1. Name any two natural indicators.
Ans: Litmus Solution/paper, red rose extract
2. Name the source from which litmus is obtained.
3. What is a neutral solution? Give an example.
4. If red litmus paper is dipped in a solution and it remains red, then what is the nature of the
solution?
5. Define salt.
6. What can you say about the nature of a solution which turns turmeric paper red?
7. Paheli is suffering from indigestion due to acidity. Is it advisable to give
her orange juice in this situation and why?
8. What name is given to the reaction in which an acid reacts with a base to?
form salt and water?
9. Curd turns blue litmus red. What does this tell about the property of curd?
10. What should be done in case of a ‘basic soil’ to make it suitable for the
growth of plants?
SHORT ANSWER QUESTIONS
1. Why is calamine solution applied in case of ant bite?
Ans: The sting of an ant contains formic acid. So, in case of ant bite, we rub soap solution or
moist baking soda or calamine lotion (ZnCO3) which neutralizes the effect of ant sting and
relieves the pain.
2. Fill the blanks in the following sentences
(a) Lemon juice and vinegar taste ___________ because they contain ----------.
(b) Turmeric and litmus are _________ acid-base indicators.
(c) Phenolphthalein gives _________ colour with lime water.

SCM VII 2025-26 TERM- 1 Page 20 of 12

 (d) When an acidic solution is mixed with a basic solution, they
_________ each other forming _________ and water.
3. Define Neutralization. Give an example.
4. Name the bases found in Lime water and soap.
5. Identify as acidic, basic or neutral solution from the following-
Lemon juice, orange juice, vinegar, milk of magnesia, baking soda,
lime water, sugar solution, common salt solution, shampoo.
6. Why ‘Milk of magnesia’ is given to a patient of hyperacidity?
7. Why slaked lime or quick lime is added to too acidic soil?
8. State the colour change of litmus, methyl orange and phenolphthalein
in acidic and basic medium.
9. State whether the following statements are true or false. Correct the false statements.
(a) All substances are either acidic or basic.
(b) A compound if acidic will turn all indicators red.
(c) Lime water turns red litmus blue.
(d) Common salt dissolved in water turns blue litmus red.
(e) Phenolphthalein is a natural indicator.
(f) Calamine can be used to treat ant’s sting.
(g) Lemon water is basic in nature.
10. A student adds dilute sulphuric acid to sodium hydroxide solution.
Will the resultant mixture become hot or cold? Why?
11. What are olfactory indicators?
12. Define acid-base indicators. Give examples.
LONG ANSWER QUESTIONS
1. Write any one use of:
a) Slaked lime b) Magnesium hydroxide
c) Citric acid d) Caustic soda

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Ans (a) Slaked lime [Ca (OH) 2] is used in white washing, in neutralizing acidic soils and in the
manufacture of toothpastes (in order to neutralize the acid produced in the teeth by
bacterial action).
(b) Magnesium hydroxide (milk of magnesia) is used to neutralize the acidity of stomach;
hence it helps in relieving stomach ache.
(c) Citric acid is used as food preservatives. These acids also provide flavour to the food.
(d) Sodium hydroxide (caustic soda) is used in the manufacture of soaps.
2. Paheli observed that most of the fish in the pond of her village were gradually dying. She
also observed that the waste of a factory in their village is flowing into the pond which
probably caused the fish to die.
(a) Explain why the fish were dying.
(b) If the factory waste is acidic in nature, how can it be neutralised?
3. In order to determine acidic, basic or neutral character of solution, a student tabulated
the following results after the experiment. Which of the following observations has been
tabulated correctly? Give reason.
CASE Test solution Colour change Colour change Acidic/ Basic /
on red litmus on blue litmus Neutral
paper paper
A NaCl No change Red Acidic
B Lime water Blue No change Neutral
C Vinegar No change No change Neutral
D Washing soda Blue No change Basic

Diagram based Questions

1. Observe the figures given below and write whether substance is acidic/basic or neutral.

2. Boojho, Paheli and their friend Golu were provided with a test tube each containing China
rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test
SCM VII 2025-26 TERM- 1 Page 22 of 12
 tube and got dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got
green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour.
Suggest the possible cause for the variation in their results.
Higher Order Thinking Skills
1. The observation made during an experiment are recorded below:

Solution A B C D
Blue litmus Reddish Deep red No change No change
Red Litmus No change No Change Blue No change

i) Which of these is, strongly acidic, weakly acidic, Neutral, Basic

ii) Which of the two solutions will react to illustrate the neutralization reaction?
2. A white shirt has a yellow stain. When soap is rubbed on the shirt, the yellow stains
turn red. On rinsing the shirt with water, the red stains turn yellow again.
a. Name the natural indicator present in the curry stain.
b. What is the nature of the soap- acidic or basic?
c. Name the indicator which will give pink colour with the soap solution.

ANSWER KEY(MCQ): 1-c; 2- d; 3-c; 4-b; 5-b; 6-a; 7-a; 8-a;

9-b; 10- a; 11-d;12-d;13-d;14-b;15-a

CLASS: VII SUBJECT: SCIENCE TOPIC: MOTION & TIME

CONCEPT MAP

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MEASURING TIME
In order to measure something, we need to have unit of measurement. A unit of
measurement is a known fixed quantity with which we compare an unknown quantity we
wish to measure.

Ancient Measurement devices

1. Sundial
• Earlier people used to measure the time by using Sundial.
• Sundial is based on the principle of shadow formation during the course of time.
• The only drawback of these sundial is that it does not work after sun set.

2.
Hour
glass

• The hourglass uses the flow of sand to measure the flow of time. They were used in
navigation.
• The time taken by sand to stream completely into the lower chamber is taken as one hour.
That is why it is also called Sand clock.
3. Water clock
It measures time by allowing water to drip slowly from one marked container into another.

Constuction

You'll need a plastic bottle, water, a marker, scissors, and a way to create a hole (like a
thumbtack or pin). First, cut the bottle in half. Then, make a small hole in the lid of one
half. Next, place the top half upside down inside the bottom half, so the lid is facing
down. Finally, fill the top half with water, and use a stopwatch or marker to track how long it
takes the water to drain into the bottom half, creating a
simple timer.

Explanation:
• The water clock works because the water flows out of
the upper container through the hole at a constant
rate.
• By marking the level of the water in the lower
container, you can measure the passage of time.

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 Modern time measuring device
1. Pendulum clock
Pendulum clock uses a pendulum as its time base. From their invention until about 1930, clocks
using pendulum movements were the most accurate. Because of their need to be stationary and
immovable while operating, pendulum clocks cannot operate in vehicles; the motion and
accelerations of the vehicle will affect the motion and pace of the pendulum, causing
inaccuracies.
2. Quartz clock
A clock driven by quartz crystal is called quartz clock. In this clock tiny
quartz crystal oscillates freely. Quartz crystal can vibrate very fast and at a
precise rate which helps in measuring time accurately.

CONSTRUCTION OF PENDULUM
To make a simple pendulum, you'll need a string, a small weight (like a metal nut or a car key),
and a way to suspend the string (a hook, nail, or tape). Attach the weight to one end of the
string and suspend the other end securely. Gently pull the weight to one side and release it to
observe the pendulum's motion. You can measure the time it takes for a set number of
oscillations to study its period.

Tips for a good pendulum:

Small angles: Keep the angle of initial
displacement small (less than 10
degrees) for the most accurate
results.
Friction: Ensure the suspension point
allows for smooth movement with
minimal friction.
Weight: Use a weight that is dense enough to swing consistently.
String length: The length of the string affects the pendulum's period (time for one oscillation).

A simple pendulum consists of a mass (a metallic ball is called bob) at the end of a pendulum
string. Terms related to pendulum.

• Periodic motion : Any form of motion that repeats itself after fixed intervals of time is called
a periodic motion.
• Mean position: The position when pendulum is at rest is called mean position.
• Oscillation: To and fro motion of pendulum about mean position is called its oscillation.
• Time period: Time taken to complete one oscillation.
• Time period =Time taken to complete
oscillations/Number of oscillations.

SCM VII 2025-26 TERM- 1 Page 25 of 12

The Time period of a simple pendulum depends on the length of the string and gravity.

KEY CONCEPTS FOR MOTION AND TIME

1 MOTION
A body is said to be in motion if its position changes with time and it is at rest if its
position does not change with time.
• Uniform motion: When an object covers equal distance in equal interval of time.
• Non-uniform motion: When an object covers unequal distance in unequal/equal interval
of time.
2 SPEED The speed of moving body is the distance it travels in a unit time.

SI unit for speed is m/s. If the speed of a body moving along straight line remains
constant, or does not change with time, we say the body is in uniform motion. If speed
changes with time, it is no longer in uniform motion.

PRACTICAL FILE:
AIM: To determine the time period of a simple pendulum using a 1-meter string and 10
complete oscillations.
Materials Needed:
• String (1 meter long)

• Small metal bob or any dense weight

• Stopwatch or timer

• Stand with clamp or a fixed support

• Meter scale/ruler

• Protractor (optional, for measuring small angle)

• Notebook and pen for recording

Procedure:
1. Set up the pendulum:

o Attach one end of the string securely to a stand or fixed support.

o Tie the other end to a small, dense bob to act as the pendulum.

SCM VII 2025-26 TERM- 1 Page 26 of 12

 o Ensure the string length from the pivot to the center of the bob is exactly 1 meter.

2. Displace the bob:

o Pull the bob to a small angle (preferably less than 15° from the vertical) to maintain
simple harmonic motion.

o Do not swing it with force; just release gently.

3. Start timing:

o Start the stopwatch as the bob passes through the mean position (central lowest
point) for the first time.

o Count 10 complete oscillations (1 oscillation = movement from one extreme to the

other and back).

4. Stop the stopwatch:

o Stop the time when the bob completes 10 oscillations and returns to the mean
position the 10th time.

5. Record the time: Note the total time taken for 10 oscillations.

6. Calculate the time period:

ASSIGNMENT QUESTIONS
MCQ
1. The 800 m world record holder ran it in 86 s. What was his speed?
(a) 9.4m/s (b) 9.6 m/s (c) 9.5 m/s (d) 9.7m/s

2. The Time of simple pendulum increase with increasing,

(a) Length (b) Amplitude
(c) Diameter of the bob (d) both (a) and (c)

3. The time period of simple pendulum is time required

(a) To complete one oscillation
(b) To complete two oscillations
(c) To go from one oscillation extreme position to another extreme position
(d) To complete movement from the mean position to extreme position
SCM VII 2025-26 TERM- 1 Page 27 of 12
4. Which of the body is moving faster: A- covers 300m in 35 Sec OR B- covers 350m in 35
Sec?
(a) A
(b) B
(c) Either A or B
(d) Both are at rest

5. Sundial is the device used to measure

(a) Time (b) Distance (c) Speed (d) All of these
6. The SI unit of speed is
(a) m/hr (b) cm/s (c) m/s (d) km/hr
7. The SI unit of time is
(a) Minute (b) hour (c) second (d) day
8. In earlier times people used to use such type of clocks and this is also used in
Jantar-Mantar. Name it.
(a) water clock (b) watch (c) sundial (d) sand clock

9. Which of the following represents the correct order from smallest to largest?
(a) Millisecond < Second < Minute < Hour
(b) Second < Millisecond < Minute < Hour
(c) Minute < Second < Hour < Millisecond
(d) Hour < Minute < Second < Millisecond
10. The mean position of a pendulum is
(a) the point at which the pendulum rests and shows no motion.
(b) the point at which the pendulum travels and no rest.
(c) both of these.
(d) none of these.

11. How many seconds are there in 1 minute?

(a) 10 (b) 60
(c) 100 (d) 600
12. Which of the following is the smallest unit of time?
(a) Minute (b) Hour
(c) Second (d) Millisecond

13. The change in position of a body over time is called __________.

(a) rest (b) speed (c) acceleration (d) motion

SCM VII 2025-26 TERM- 1 Page 28 of 12

14. The device which is used for measuring time intervals in sports activities is called ________.
(a) wrist watch (b) stop watch (c) stop clock (d) quartz watch

15. If a car travels 100 km in 2 hours, what is its speed?

(a) 20 km/h (b) 50 km/h
(c) 100 km/h (d) 200 km/h

II. Very short answer questions:

1. Define uniform speed.
→ Uniform speed is when an object covers equal distances in equal intervals of time.
2. Give an example of non-uniform motion.
→ A car moving through traffic is an example of non-uniform motion.
3. What is the formula for speed?
→ Speed = Distance ÷ Time
4. What is the SI unit of speed?
→ Metres per second (m/s)
5. If a car covers 60 km in 1 hour, what is its speed?
→ Speed = 60 km/h
6. Name the physical quantity that tells how fast an object is moving.
→ Speed
7. What do we call the motion when speed changes over time?
→ Non-uniform motion
8. If a train travels 120 km in 2 hours, what is its average speed?
→ Average speed = 60 km/h
9. Which type of motion does a freely falling object exhibit: uniform or non-uniform?
→ Non-uniform motion
10. A spaceship travels 36,000 Km in one hour. Express its speed in km/s.
11. What is a candle clock made of?
12. How does a candle clock measure time?
13. How does a hour glass measure time?
14. What does an odometer measure?
15. What does a speedometer show?
III. Short Questions:
1. What are the limitations of a sundial?
Ans It cannot be used for measuring time during night and cloudy days.

2. A policeman cycles 4.2 km to work every morning. If it takes him 10 minutes, what is his
speed? [Hint: we need to change the distance into metres, and time into sec]
3. A car moving at speed of 45km/hr takes 5hr to reach its destination. Find the distance
covered by the car.
4 Which of the two is moving faster?

SCM VII 2025-26 TERM- 1 Page 29 of 12

 a) A car covering a distance of 400 km in 5 hour or
b) A train covering a distance of 500 km in 6 hours.
5. Define oscillation and time period of a pendulum.
6. If the time period of a pendulum is 1.2 seconds, how much time will it take to complete 25
oscillations?
→ Time = Time period × Number of oscillations = 1.2 × 25 = 30 seconds
7 Describe various ways of defining one oscillation from the given figure.

A B C
the the

8 It takes 100 seconds for a pendulum to make 50 complete oscillations. Calculate the time
period.
→ Time period = 100 ÷ 50 = 2 seconds
9 A lion covers a distance of 100 m in 10 s. Calculate the speed of the lion in:
Time(sec) 0 4 8 12
(a) m/s (b) km/h
Distance(m) 100 200 300 400
10 How can we decide among the two objects in motion, which one is faster and
Time(sec) 0 4 8 12
which one is slower? Distance(m) 100 200 300 400

Long question answers type:

1. (a) What is the principle behind the working of all-time measuring devices?
(b How can we change the time period of a simple pendulum?
(i) All time measuring devices are based on periodic motion.
(ii) We can change the length of the string of the pendulum to alter its time period.

2. Match the items of Column A with those in Column B.

SCM VII 2025-26 TERM- 1 Page 30 of 12

3. The bob of a simple pendulum takes 0.25 s to move from one extreme position to the
mean position. What is the time period of the pendulum?

Diagram based Question

1. A bus starts from bus terminal at 6 a.m. in the morning. It travels with a speed of 30 km for
next one hour, and then travels for next one hour with a speed of 40 km. Calculate
Average speed of bus. (Ans 35 km/hr)

3. A train travels 90 km at a speed of 45 km/h. How much time does it take to cover the
distance? Give your answer in hours and minutes. ( 2 hours)
4. True/False

(a) The unit of meter is written as “m” in lowercase. (True)

(b) “Kg” should be written with a capital “K” and lowercase “g”. (False)
(c) The unit of time, second, is written as “S”. (False)
(d) Unit names are always written in lowercase, even if named after a person. (True)

Activity based question:

1. Determine the time period of a simple pendulum of length 50 cm and complete the
following table. What do you infer from this activity? Does time period change with the
change in number of oscillations as long as the length of pendulum remains same?

S. No No. of Stopwatch reading(s) Total time Time

oscillation taken for period
Initial Final
oscillations
1 20
2 22
3 25
4 27

Q2. A fast runner attains a maximum speed of 10 meter per second. what we will be his speed in
kilometre per hour?
Higher Order Thinking Skills:
SCM VII 2025-26 TERM- 1 Page 31 of 12
1. Observe the following figure: Time taken by the bob to move from A to C is t1 & from C to O
is t2. Then what will be the time-period of this simple pendulum.

ANSWER KEY (MCQ): 1-a ; 2- a; 3-a; 4-b; 5-a; 6-c; 7-c; 8-c;
9-a; 10- a; 11-b;12-d;13-d; 14-b; 15-d

ACTIVITY:

Learn how people told time before the invention of watches and clocks by making a sun clock.

MATERIALS REQUIRED: Crayons, Paper plate, Sharpened pencil, Push pins, Ruler, Plastic straw.

STEPS:

1. Prepare Paper Plate

o Start this project on a sunny day just before noon.

o Use the pencil to poke a hole through the very centre of the paper plate. Write the
number 12 on the edge of the plate with a crayon. Using the ruler as a guide, draw a
straight line from the number 12 to the hole in the centre of the plate.
2. Take Plate Outside
At noon, take the plate and the straw outside. Put the plate on the ground and poke the
straw through the hole. Slant the straw toward the line you drew. Now carefully turn the
plate so that the shadow of the straw falls along the line to the number 12.
3. Fasten Plate to Ground
Fasten the plate to the ground with some pushpins. Predict where do you think that the
shadow of the straw will be pointing in
one hour.
4. Check Shadow Position Hourly
One hour later, at one o’clock, check
the position of the shadow along the
edge of the plate and write the
number 1 on that spot. Continue each
hour predicting the position and then
checking and marking the actual
position and time on the edge of the
plate.
5. Discuss Your Sun Clock At
the end of the day you will have a sun
SCM VII 2025-26 TERM- 1 Page 32 of 12
 clock. On the next sunny afternoon, you will be able to tell time by watching where the
shadow of the straw falls on your clock.

CONCEPT MAP

SCM VII 2025-26 TERM- 1 Page 33 of 12

INTRODUCTION
If we enter a dark room, the objects present in the room are not visible. However, if
we switch on a bulb, everything in the room becomes visible. Why?
Light is a form of energy which helps us in seeing objects. When light falls on an object,
some of the light gets reflected. The reflected light comes to our eyes, and we are able to
see an object.
"Light is an invisible energy, which causes in us the sensation of vision."

SOURCES OF LIGHT
An object which emits light is called a source of light. All sources of light can be classified into
two categories, namely, natural, and man-made/ artificial sources of light.

Natural Sources of Light: Sun is the primary source of light for planet Earth. Besides the sun and
the stars, we have an interesting natural source of light close to us here on the earth itself. It is
the 'firefly' (glow-worm) commonly known as the 'jugnu'.

Artificial Sources of light: Besides these natural sources, we have many man-made or artificial
sources of light. We need these artificial sources at night when there is no sunlight around. The
electric lamp, a burning candle and the kerosene lamp are the common artificial sources of
light.

LUMINOUS BODIES: All bodies which emit light energy by themselves are called luminous
bodies. The examples are sun, burning candle, glowing electric lamp, firefly or jugnu etc.

NON-LUMINOUS BODIES: Objects which do not emit their own light but reflect the light
falling on them, are called non-luminous objects. The moon is a non -luminous object.

SCM VII 2025-26 TERM- 1 Page 34 of 12

TRANSPARENT, TRANSLUCENT AND OPAQUE OBJECTS

Materials can be classified based on the amount of

light they transmit.

Materials, which allow complete transmission of light,

are called transparent. Any object can be seen through
the transparent material. Examples of transparent
material are pure glass and clean air.

Opaque materials either reflect or absorb any incident

light. As a result, light rays cannot pass through
opaque materials. Wood, stone, metal etc., are opaque
materials.

Translucent materials allow partial transmission of

light through them. A part of the incident light may get
reflected or scattered as it passes through the interior
of the material. Any object, seen through a translucent
material, appears fuzzy or blurred. Some examples are
oily paper, tissue, some plastics frosted glass, etc.

The invention of the blue LED (light-emitting diode) was awarded the Nobel Prize in Physics
in 2014. The prize went to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for their
work in the early 1990s.
Blue LEDs were the missing piece needed to create white LED light, by combining red,
green, and blue LEDs.
This led to energy-efficient, long-lasting, and environmentally friendly lighting,
revolutionizing the lighting industry.
LEDs operate at a forward voltage between 1.8V and 3.5V, depending on the colour.

SCM VII 2025-26 TERM- 1 Page 35 of 12

SCM VII 2025-26 TERM- 1 Page 36 of 12
EVERYDAY PHENOMENA WHICH SUGGEST THAT LIGHT TRAVELS IN A STRAIGHT LINE

• There are number of phenomena which suggest that light travels in straight lines.
• Formation of day and night suggests that light travels in straight lines. If these were not
so, the light would have curved around the earth and there would have been sunlight
during night too.
• Formation of shadows suggests that light travels in straight lines.
• The beam of light coming from the projection room in the cinema hall suggests that light
travels in straight lines.
• The light coming from small laser torch used as pointer, suggests that light travels in
straight lines.
• This property of light by which it travels in straight lines is called rectilinear propagation
of light.

THE PINHOLE CAMERA

How to make it?

Take two boxes so that one can slide into another with no gap in between them. Cut open
one side of each box.
On the opposite face of the larger box, make a small hole in the middle
In the smaller box, cut out from the middle a square with a side of about 5 to 6cm.
Cover this open square in the box with tracing paper (translucent screen)
Slide the smaller box inside the larger one with the hole, in such a way that the side with the
tracing paper is inside. Now it is ready to use.

How to use it?

Hold the pin hole camera and look through the open face of the smaller box. You should use a
piece of black cloth to cover your head and the pinhole camera.
Now focus on the object you want to capture in the camera. Make sure that the objects you
wish to look at through your pinhole camera are in bright sun.
Move the smaller box forward or backward till you get a picture on the tracing paper pasted at
the other end.
How the Images look like in pin-hole camera?

SCM VII 2025-26 TERM- 1 Page 37 of 12

Upside down (inverted) images are formed. Image in a pinhole camera is real, Inverted, and
smaller in size.

SCM VII 2025-26 TERM- 1 Page 38 of 12

Natural Pin-hole Camera

When we pass under a tree covered with large number of leaves, we notice that small patches
of sunlight under it. These circular images are, in fact, pinhole images of the Sun. The gaps
between the leaves, act as the pin holes. These gaps are all kinds of irregular shapes, but we can
see circular images of the Sun. This is called Natural Pinhole camera.

Advantages of Pinhole Camera

A pinhole camera does not require focusing like modern day cameras.
Since lens is not used in a pinhole camera, there is no distortion of image.

Disadvantages of Pinhole Camera

In a pinhole camera the image is captured on the screen, hence it cannot be recorded.
The image does not give the finer details of the object and also a pinhole camera is not
suitable for capturing the moving image.

SHADOWS
When an opaque object is placed in path of light, a dark portion is formed on the opposite side
of object on the screen. This dark portion is shadow. A shadow is formed whenever the path
of light is obstructed by an opaque object.
The formation of shadows is a natural phenomenon that again demonstrates that light
ordinarily travels along straight lines.

CHARACTERISTICS OF SHADOW
• The size of shadow depends on the distance of source of light and on the angle at which
the light rays fall on the object.
• If the source of light is closer to the object, a larger shadow is formed than when the
source of light is far from the object.
• The shadow can be seen only on a screen. The ground, walls of the rooms, a building, or
other such surfaces act as a screen for the shadows you observe in everyday life.
• Shadows are black in colour, and this is not changed by the colour of the opaque objects.
So, a red and yellow rose will have same black shadows.
• The shadow of an object is erect. Hence, we can identify an object from its shadow.

We need three things to observe a

shadow:
1. a source of light
2. an opaque object
3. a screen on which the shadow can

SCM VII 2025-26 TERM- 1 Page 39 of 12

 be seen.

REFLECTION OF LIGHT:
The phenomenon of bouncing back of light from the
surface of an object is called Reflection.

We see our face in the Mirror. This is possible through the

phenomenon of reflection of light. Basically, Light rays reflected
from parts of our body fall on mirror and are reflected. When
these reflected rays reach our eyes, we can see the image in the
mirror. So, reflection of light is changing the direction of the light.

Image formation by Plane Mirror:

The image formed is erect, same size and laterally inverted. It retains the same colour as the
object.
Lateral Inversion: The right side of the object appears to be the left side of its image
and vice-versa. This phenomenon in which left-right positions are reversed is called lateral
inversion.

SCM VII 2025-26 TERM- 1 Page 40 of 12

INCIDENT RAY AND REFLECTED RAY OF LIGHT:
The ray of light that falls on the mirror is called the incident ray.
The ray of light that bounces back from the mirror is called the reflected ray.
Normal ray - a line drawn perpendicular to a surface at the point where a light ray strikes
it (the point of incidence). It's a reference line used for measuring angles in reflection and
refraction

Difference between the image and shadow of an object:

IMAGE SHADOW
1. Image gives detailed information like 1. Shadow gives only the outline of the
the colour, texture, structure of the object. object.

2. Image is formed due to reflection of light 2. Shadow is formed due to obstruction

from a smooth polished surface. in the path of light by an
opaque body.

3. Image undergoes lateral inversion 3. Does not go under lateral inversion.

(Reversal of left-right).

Facts: Aranmula Kannadi – Mirror

➢ Metal Mirror- Made from a special copper-tin alloy—no glass

used.
➢ Handcrafted: Each piece is handmade and takes days to polish.
➢ Unique to Kerala- Only made in Aranmula, Kerala; has GI tag.

SCM VII 2025-26 TERM- 1 Page 41 of 12

 ➢ No Distortion: Reflects from polished metal surface
➢ Shatterproof: Doesn’t break like glass mirrors.
➢ Secret Formula: Craft and composition are kept within artisan families.
➢ Cultural Symbol: Used in Kerala rituals and believed to bring good luck.

EXPERIMENT -To demonstrate that light travels in a straight line. (To be written in
Practical File)

AIM: To demonstrate that light travels in a straight line

MATERIALS REQUIRED: A rubber or a plastic tube about 2 feet long, a small candle and a match
box.
PROCEDURE:
Light a candle and fix it on a table at one end of the room.

Then standing at the other end of the room look at the candle through a pipe. Now bend
the tube, again look through the tube.

OBSERVATION:
In the first case we will be able to see the flame of the burning candle.
In the second case we will notice that flame of the burning candle is no longer visible.
INFERENCE:
This suggests that light cannot bend around, and hence, it travels in straight line.
PRECAUTIONS:
Should be careful while lighting the candle. The rubber tube should be held properly.

ASSIGNMENT

I MCQ
1. Opaque objects-------------
a. Allow light to pass through them.
b. reflect light falling on them.
c. emit light.
d.do not allow light to pass through them.
2. A is /is not a source of light.
(a) Firefly (b) metal strip (c) star (d) burning candle.
3. Metals are shiny because of --------------- - 4. A emits light energy.
(a) Reflection of light (a) Firefly (b) bat
(b) Absorption of light

SCM VII 2025-26 TERM- 1 Page 42 of 12

 (c) rectilinear propagation
(d) Radiation of light

(c) cricket (d) rat

SCM VII 2025-26 TERM- 1 Page 43 of 12

5. The image formed by a pinhole camera is.
(a) Similar as the image formed by mirror.
(b) Similar as the shadow.
(c) Upside- down and proves that light travels in straight line.
(d) Distorted in comparison with the object.
6. Sunlight can pass partially through.
(a) Walls (b) a wire mesh (c) rocks (d) Iron plate
7. Which of the following statement is incorrect about a mirror?
(a) Light travelling along a straight path gets reflected from a mirror.
(b) We see the mirror image as left-right reversed.
(c) When we stand in front of a mirror, we can also see the image of other
nearby objects.
(d) Mirror images are same as shadows.
8. The shape of shadow depends on:
(a) the shape of the object
(b) the position of source of light
(c) the size of the source of light
(d) all above
9. There is light on the earth even on a dark, cloudy day. This is because clouds are:
(a) Opaque (b) Transparent (c) Translucent (d) Luminous
10. Find the odd one out:
(a) the moon (b) the sun (c) the stars (d) Jugnu
11. Shadow is short when sun is overhead at
(a) Noon (b) Night (c) Midnight
(d) Sunset
12. People cast shadow on ground as they walk because they block.
(a) View (b) Light (c) Scene (d) Way
13. A tracing paper will make a shadow with less.
(a) Dark (b) Size (c) Color (d) Shape
14. Which is a device to image the sun?
(a) Plane mirror (b) Pinhole camera
(c) A straight pipe (d) Glass slab
15. Out of these, which one is not a man-made luminous body?
(a) Electric bulb (b) Burning candle
(c) Firefly (Jugnu) (d) Oil lamp

SCM VII 2025-26 TERM- 1 Page 44 of 12

ANSWERS
1. (d) 2. (b) 3. (a) 4. (a) 5. (c) 6. (b) 7. (d) 8. (d) 9. (c) 10. (a) 11. (a) 12.
(b)
13. (a) 14. (b) 15. (c)

II Very Short Answer Questions

1. Name two natural sources of light.
Ans: - The Sun, The stars
2. Name three manmade sources of light.
3. Give an example of living beings which emits light.
4. On which principal pinhole camera is based?
5. Does the moon emit light?
6. Can we see the shadow of a transparent object?

SCM VII 2025-26 TERM- 1 Page 45 of 12

7. Name two surfaces which can act as screen for obtaining shadows in
everyday life.
8. At what time of the day is the length of the shadow longest and shortest?
9. Why is it difficult to see through a frosted glass window?
10. Is vacuum an opaque body?

III Short Answer Questions

1. Classify the following as transparent, translucent, and opaque bodies. Stone, oil
patched paper, reading glass, and skin of drum, wood, smoke Fog, iron bar, wire
mesh, cardboard, a CD, water.
Ans:-Transparent-reading glass, water
Translucent - oil patched paper, skin of drum, smoke, fog, wire mesh, Opaque --- stone,
wood, iron bar, cardboard, a CD.
2. Can you think of creating a shape that would give a circular shadow if held in
one way and a rectangular shadow if held in another way?
3. In a completely dark room, if you hold up a mirror in front of you, you will see
a reflection of yourself in the mirror. Explain your answer.
4. Draw the mirror image of the word PLANE.
5. What is shadow? How is it formed?
6. Is air around us always transparent? Give reason.
7. Using a pinhole camera, a student observes the image of two of his friends,
standing in sunlight, wearing yellow and red shirt respectively. What will be the
colors of the shirts in the image?

IV Long Answer Questions

1. Write three characteristics of shadows.
Ans: - (1) A shadow is a dark outline of the
object.
2. The shape of a shadow may or may not match with that of object. It all
depends on the position in which the object is held in the path of light.
3. The size of the shadow depends on the size of the light source and object,
and on the distance between the light source, the object and the wall or
screen. It can be smaller, equal, or bigger than the object depending upon its
distance from the source of light.
4. VIIWhat
SCM do you
2025-26 understand
TERM- 1 by the term reflection of light? Name two objects
Page 46 of 12
which can reflect light.
 5. Explain how we see our image in the Mirror?
V Higher Order Questions
1. On a sunny day, does a bird or an aero plane flying high in the sky cast its shadow on the
ground? Under what circumstances can we see their shadow on the ground?
Solution:

No, a bird or an aero plane flying high in the sky cannot cast its shadow on the ground even
on a sunny day because light travels in straight line and the shadow becomes scattered or
too faint before reaching the ground due to the greater distance or higher altitude. We can
only see their shadow on the ground if they are flying very close to the ground.

2. Imagine you are in a room with mirrors on all four walls. What patterns of light and
reflection would you expect to see if a torch is turned on in the center of the room? Explain
your reasoning.

VI Diagram based Questions

1. What does the following experiment demonstrate?
Ans: Light travels in a straight line.
2. Three torches A, B and C, shown in figure are
switched on one by one. The light from which of the
torches will not form a shadow of the ball on the screen.

3. Name the electrical component

shown in the figure. Label the positive
and negative terminals and draw the
circuit symbol for the component as well.

VII Case-Based Questions

Case Study: LED Lamps and Light Pollution
India is promoting the use of LED lamps due to their energy efficiency and eco-friendliness.
However, improper disposal of LED waste is becoming an environmental concern.

1. Which of the following is a correct environmental approach to handling used LED

lamps?
a) Burn them in open air b) Throw them with regular garbage
SCM c)
VIICollect
2025-26and send
TERM- 1 them for recycling d) Bury them underground Page 47 of 12
 2. How does LED usage help in reducing light pollution, especially in natural
ecosystems?
a) By producing brighter blue light
b) By emitting directional light that can be better controlled
c) By turning off automatically during the day
d) By increasing the number of artificial light sources

Suggested Science Activities

1. Construct a Sundial
o Create a simple sundial using basic materials.

o Use it to tell the time during different parts of the day.

o Compare your sundial readings with a clock to evaluate its accuracy and

understand how the position of the sun affects timekeeping.

2. Build Working Models of a Kaleidoscope and a Periscope
o Design and assemble your own kaleidoscope to explore the principles of

reflection and symmetry using mirror.

o Construct a periscope to understand how light travels and how mirrors can

be used to change the direction of vision using mirrors and pipe.

3. Design and Build a Solar Cooker
o Use reflective and insulating materials to create a solar cooker.

o Test it by cooking or warming food using only sunlight.

o Learn about renewable energy and the practical applications of solar power.

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