KBTC INTERNATIONAL SCHOOL

Cambridge Lower Secondary Course

REVISION NOTE
Secondary One
CHEMISTRY
(2024-2025 Academic Year)
 UNIT -2
Materials and their structure
2.1 Solids, liquids and gases
States of Matter - Everything we can see and feel is called matter. There are three states of matter which are
solids, liquids and gases.

Properties of Solid, Liquid and Gas

Particle Theory
The particles are arranged differently in solids, liquids and gases.

Attractive force between particles

 The attractive force holds the particles together.
 The force can stop the particles from moving around the solid because of fixed pattern.
 In liquid, the attractive force between the particles is weak enough to allow them to move but strong
enough to hold them together.
 In gas particles, there is no attractive forces between them and they can move easily.
2.2 Change of State
The diagram summarizes the common changes of state.
 A change of state is a physical change in a matter. They are reversible changes and do not involve
any changes in the chemical makeup of the matter.
 Common changes of the state include melting, freezing, sublimation, deposition, condensation, and
vaporization.

Evaporation, Melting and Boiling

 Energy must be transferred, by heating, to a substance for these changes of state to happen. During
these changes the particles gain energy. This is used to overcome forces of attraction between particles.
 Evaporation can take place below the boiling point of a substance.
 Boiling happens at the boiling point, when the rate of evaporation is much faster.
 The temperature at which a liquid boil is called the boiling point.
 The boiling point of water is 100°C.
 The temperature at which a solid melt is called the melting point.
 The melting point of a solid is 0°C.
 The freezing point of liquid is 0°C.

Condensing and Freezing

 Energy must be transferred from a substance to the environment for condensing and freezing to happen.
 During these changes of state, the particles lose energy as forces of attraction form between them.

2.4 The Water Cycle

 Water is vital for all living things. Our bodies are made up of at least 60% water.
 The water moves between rivers, lakes, oceans, the atmosphere and the land. It is recycled over and
over again in a continuous system called the water cycle.
Water moves into the atmosphere
- Evaporation happens when the temperature of water in the rivers, lakes and oceans increases and some of
the liquid water forms water vapor.
- Water can also evaporate into the atmosphere from plants which is called transpiration.

Water in the atmosphere cools down

- Condensation happens as the water vapor goes up to the atmosphere, it cools and changes back into little
droplets of water in the air.

Water falls from clouds

- Precipitation happens when the water drops in the clouds fall back to Earth as Rain. The drops become
colder, then form snow, hail or sleet.
Water falls on the Earth
- The precipitation that falls then collects in rivers and open water such as large lakes and the oceans.

Water in the ground

- Some of the water from precipitation will soak into the soil and rocks as ground water.
- Water that reaches the surface of the land may flow directly across the ground into the rivers, lakes and
oceans. This water is called surface run-off.

2.5 Atoms, elements and the Periodic Table

 Atoms are tiny pieces of matter and cannot be divided.
  Carbon nanotubes- a tube made of carbon. (nano – very, very small)

Different types of atoms

 94 different types of atoms – naturally in the universe
 24 kinds of atom – in laboratories
 Total – 118 atoms

Element - What is an element?

 An element is a substance that made of one kind of atom. (Examples, Gold, Silver and Carbon)

Elements on Earth - The various elements that are found in Earth Crust

Atoms joining together

Some substances are made up of individual atoms.
 A piece of gold is made up of millions of individual gold atoms.
 Neon is a gas – is made of individual neon atoms.

Molecules- group of atoms joined tightly together is called a molecule. In oxygen and sulfur, atoms joining
together to form small particles.
Arranging the elements - The Periodic Table

 The periodic table is organized into rows and columns.

 The rows are called period. Ongoing from left to right in a period.
 The columns are called groups. Ongoing from top to bottom in a group.
 Left of dark line – metal
 Right of dark line – non-metal
 Along each of dark line – metalloids
 Group IA – alkali metals
 Group IIA – alkaline earth metals
 Group VIIB – halogens
 Group 0 – noble gases or inert gases
 Empty space (middle part of periodic table) – transition metals

Chemical Symbols
No Element Symbol No Element Symbol
1 Hydrogen H 11 Sodium Na
2 Helium He 12 Magnesium Mg
3 Lithium Li 13 Aluminum Al
4 Beryllium Be 14 Silicon Si
5 Boron B 15 Phosphorous P
6 Carbon C 16 Sulfur S
7 Nitrogen N 17 Chlorine Cl
8 Oxygen O 18 Argon Ar
9 Fluorine F 19 Potassium K
10 Neon Ne 20 Calcium Ca
Gold – Au Silver – Ag
2.6 Compounds and Formulae
 Compound – many substances are made up of more than one kind of atoms or different types of atoms
are joined tightly together.

Chemical bond = Chemical compound

Metal + Non-metal – ionic bond or ionic compound
Sodium + Chlorine → Sodium chloride (Common Salt)

Naming Compounds
There are important rules to remember when naming compounds.
1. If the compound contains a metal, then the name of the metal
comes first in the name of the compound.
2. If the compound contains a non-metal, the name of the non-metal
is usually changed. For example, the compound made from sodium
(a metal) and chlorine (a non-metal) is not sodium chlorine, but
sodium chloride.
3. When two elements form a compound, the name often ends in ‘ide’.

Some compounds contain two different elements, plus a third element–oxygen. These compounds often
have names ending with ‘ate’. For example, a compound of calcium, carbon and oxygen is called calcium
carbonate.

Carbon dioxide particles are made up of one carbon atom joined to two oxygen atoms. ‘Di’ means two.

Carbon monoxide particles are made up of one carbon atom joined to one oxygen atom. ‘Mon’ or ‘mono’
means one.

Naming Oxide
1. Mono
2. Di
3. Tri
4. Tetra
5. Penta
6. Hexa
7. Hepta
 8. Octa
9. Nona
10. Deca

Particle diagrams

Using Formulae

Remark: two elements – bonded with, three elements – bonded together

 UNIT 5
Properties of Materials
5.1 Metals and Non-metals
Metals
Metals are strong and tough. They do not shatter when dropped and they do not crack easily. They can
hold large weights without breaking.
Properties of Metals
1. Metals are shiny when they are freshly cut or polished.
2. Metals can be bent to shape them. Metals are malleable, which means they can be hammered into shape.
3. Metals are ductile, which means that they can be drawn out into wires.
4. Metals make a ringing sound like a bell when they are hit: the word for this is sonorous. (e.g., cymbals)
5. Most metals do not melt easily. They have high melting points and high boiling points. Mercury is the
only metal that is liquid at room temperature.
6. Metals are good conductors of heat. When you touch them, they conduct heat energy away from the hand
so, they feel cold. (e.g., steel)
7. Some metals are magnetic. Iron, steel, nickel and cobalt are magnetic.

Examples of some metals and their uses.

Remarks:
Need to remember that:
• the surface of most metals will become dull after a while
• big lumps of metal are hard to test for flexibility
• bottles and cups also make a ‘ringing’ sound when they are hit, but they are not made of metal.

Non-metals
Non-metals are often very useful because of the chemical reactions they have with other substances.

Properties of Non-metals
1. Non-metals look dull. They do not reflect light very well and the surface is not as smooth as metals.
2. Non-metals that are solids are brittle. If you drop them, they may shatter.
3. Most non-metals do not conduct heat energy well. This is very useful because some of them can be used to
make handles for cooking pans, for example.
4. Most non-metals do not conduct electricity. This is very useful because some can be used to make coverings
for electric plugs and cables, for example. They are known as insulators; this means they do not conduct heat
or electricity.
5. Non-metals are not as hardwearing as metals.
6. Many non-metals are gases.
7. The non-metals that are not gases have low melting points and low boiling points.
 Examples of some Non-metals and its uses

Comparison between Metals and Nonmetals

Metals Non-metals

Metals are shiny (metallic lustrous). Non-metals are dull except iodine

They conduct heat energy well. They do not conduct heat energy well.
They do not conduct electricity except
They conduct electricity. They are
graphite. Most of nonmetals are poor
good conductors.
conductors or insulators.
They are malleable and ductile They do not malleable and ductile.
All the metals are hard, strong and do Most nonmetals are brittle except
not shatter (do not crack easily). diamond
Most of metals are solids at room Nonmetals may be solid or liquids or
temperature except mercury. gases at room temperature

Metal mixtures
Alloys: Metal mixture (mixing different metals together and melting them) The properties of the alloys are
different from the metals they contain.
Brass and Bronze
Brass: An alloy of copper and zinc.

Note
 Copper and zinc have just one temperature listed.
 However, brass has a range of temperatures. There are many different types of brass, which are made by using
different amounts of copper and zinc.
 So, there is no specific melting point for brass; it depends on the proportions of copper and zinc that have
been used.
Bronze: an alloy of copper and tin
Using the properties of materials to separate mixtures Mixture:
Mixtures contain different substances that are not combined together chemically.

Separating mixtures

Mixture Type of mixture Separation Technique

Iron and sulfur Solid-solid Magnetic separation
Dry rice and pea Solid-solid Sieving
Copper sulfate and water Solid-liquid Evaporation
Food dye and water
Liquid-liquid Simple Distillation
Water and alcohol
Sandy and salty water Solid-liquid Filtration and evaporation
Mixture in which one component
Ammonium chloride and sand Sublimation
can sublime.

Distillation apparatus

Filtration and evaporation apparatus

5.5 Acids and Alkalis

Acid: any substance that form an aqueous solution with pH less than 7. (sour taste)
Base: Any substance with a pH greater than 7. (bitter taste)
Alkalis: A base that dissolves in water to form a solution with a pH greater than 7.

Physical Properties of Acids

1.Acids have a SOUR taste
2. All acids can dissolve (SOLUBLE) in water
3. Acids solutions turn BLUE litmus paper RED
4. Most acid solutions are Corrosive, Toxic and Irritate
5. All acids can conduct electricity when dissolve into water.
 Remark:
 Strong acids are mineral acids.
 Common acids in laboratory are hydrochloric acid, sulfuric acid and nitric acid.
 Hydrochloric acid is also known as stomach acid and sulfuric acid is sometimes called battery acid.

Weak Acids

Physical Properties of a Base or alkali

 Feel Slippery
 Bitter taste
 Corrosive
 Can conduct electricity when dissolve into water.
 Turns red litmus paper blue.

Remark:
 Some acids and alkalis are strong and dangerous. They are toxic, hazardous, corrosive (chemical burn,
dissolve the skin) and irritate the skin.
 Diluted acids and alkalis might be less dangerous but still harmful.

Hazard Warning Labels

Many chemicals are hazardous. Their bottles are clearly labelled with hazard warning symbols to handle them
carefully.
Indicators and pH scale
Indicator: substances that change color when they are added to acidic or alkaline or neutral solutions.
Indicators can be made from the brightly colored berries, flowers and other parts of plants. These include:
• red cabbage
• blackcurrant
• beetroot.
Remark:
 An indicator turns one color in an acid and turns a different color in an alkali.
 Red cabbage indicator turns red color in an acid, blue color in water (neutral substance) and yellow in
an alkali.

Litmus
 Litmus is a very common indicator. It is a dye and made from living things. It is also termed as natural
indicator.
 Usually use litmus paper, which is made by soaking absorbent paper in litmus solution.
 Litmus turns red in acids.
 Litmus turns blue in alkalis.
 Litmus turns purple when it is in a neutral substance.
 A neutral substance is one that is neither acid nor alkali.
 Litmus turns purple in water. Water is neutral. This means water is neither an acid nor an alkali.
Other indicators (Universal indicators)
 Universal indicator shows how acidic or alkaline a substance is.
 The acidity or alkalinity of a substance is one of its chemical properties.
 Universal indicator can change to many different colors.
 Universal indicator is made up of a mixture of different indicators.

 The strength of acids and alkalis is measured on the pH scale.

 Universal indicator changes color and shows the pH of a substance.
 The pH of a substance is one of the chemical properties of that substance.

Unit 8
Changes to Materials
8.1 Simple Chemical Reaction
What is a chemical reaction?
A chemical reaction is a process where one or more two substances (reactants) change into one or more new
substances (products).
When do a chemical reaction occur?
Chemical reaction occurs when substances undergo chemical properties changes to form new substances.
What are reactants?
Reactants are starting materials that take part in a chemical reaction.
What are Products?
Products are new substances formed after a chemical reaction.
 Physical and Chemical Properties of a Substance
Physical Properties
 what color it is
 if it is a solid, liquid or a gas
 what its boiling or melting temperature is
 if it is heavy or light
Chemical Properties
 how acidic or alkaline it is
 how it reacts with water, acids or metals
 how readily it reacts
 pH value
Physical Change and Chemical Change
Physical change
In a physical change, no new substances are formed. It is often just a state change. E.g. ice melting.
Chemical change
In chemical change, new substances are formed. The products are not easily changed back or reversed.

Chemical Equation
A chemical equation is a representation for a chemical reaction.
Reactant(s) Product(s)
Remark:
 In some chemical reactions, a substance breaks apart to make new substances. For example, water can
be split apart to form oxygen and hydrogen.
 Chemical reactions happen everywhere including plants, animals and human.

Burning
 Burning is a chemical reaction. When a substance burns, the substance reacts with the oxygen in the air.
The new substances are called oxides.
 When a metal burns, it will combine with oxygen in the air to from metal oxide. For instance, when
magnesium metal is burnt, a white powder is formed. This powder is magnesium oxide.
 When a nonmetal burns, it will combine with oxygen in air to from nonmetal oxide. For example, when
carbon burns it combines with oxygen in the air to make the gas carbon dioxide.
Metal + oxygen metal oxide
e.g. magnesium + oxygen magnesium oxide
Iron + oxygen iron oxide (rust)

Nonmetal + oxygen nonmetal oxide

e.g. carbon + oxygen carbon dioxide
 The scientific term for burning is combustion.

Reactions with water

Some substances react very violently with water.
Some substances do not react with water at all.
When a metal reacts with water, a metal hydroxide and hydrogen gas would be form.
Metal + water metal hydroxide + hydrogen
When a very small piece of potassium is placed in a large trough of water, hydrogen gas is given off. The reaction
produces so much heat that the gas burns.
Potassium + water potassium hydroxide + hydrogen
Calcium + water calcium hydroxide + hydrogen
Remark:
Potassium (a metal) is very soft and can be cut with a knife. This is a physical property. Potassium is so reactive
that it has to be stored under oil to prevent it reacting with the water vapor in the air. This is a chemical property.

Reactions with acid

 When a metal reacts with a dilute acid, salt and hydrogen gas would be formed. For example, when
magnesium is placed in hydrochloric acid, bubbles of gas are given off. The gas is hydrogen, and
magnesium chloride has been formed.

Remark:
1. Hydrochloric acid must be diluted for this reaction.
2. Dilute acid means the acid which contains large amount of water.
3. The type of salt formed depends on the type of acid used.

4. The reaction of metal with dilute acid can be used to prepare hydrogen gas in a laboratory.
 Laboratory Preparation of Hydrogen Gas

How to Collect Hydrogen Gas?

 Hydrogen gas can be collected by downward displacement of water or over water method.
 Collection method is chosen based on the physical properties of hydrogen gas.
 It is colorless, odorless and tasteless gas.
 It is lighter than air and slightly soluble (almost insoluble) in water.
 It is a combustible (burn itself) gas but does not a support of combustion.

Teat for Hydrogen gas (Squeaky pop test)

A lighted splint or match is placed to the mouth of the test tube or gas jar. If the gas id hydrogen gas, it will burn
with squeaky pop.

Neutralization
Neutralization is a chemical reaction in which an acid and an alkali react (cancel out) together to from salt and
water (neutral solution).
Acid + Alkali salt + water
Making a neutral solution
You can use a special piece of equipment called a burette to neutralize an alkali very accurately

If you use hydrochloric acid and sodium hydroxide (an alkali), these are the reactants. When they react together,
the products that form are sodium chloride and water.

Neutralization in Daily Life

Antacid is a medicine used to cure indigestion problem. It

contains an alkali to neutralize acid stomach.
The most common alkalis in antacids are magnesium hydroxide
Mg (OH)2, aluminium hydroxide Al (OH)3 etc.

Because of the release of formic acid, ant bites and bee stings
cause inflammation, irritation, and pain all around the infected
area.
Bases such as baking soda, and baking powder, are applied to the
infected area to neutralize the formic acid ejected by bee or ant
stings.

The bacteria that feed on food particles in our mouth produce

acid. The acid decays out teeth.
The base or alkali in toothpaste can help to neutralize the acid in
our mouth.
 The excessive use of chemical compounds, pesticides, and fertilizers,
makes the soil acidic or basic in nature.
If the soil is acidic, bases like calcium oxide, calcium hydroxide and
so on can be used to neutralize it.

The acid rain damages trees and changes the pH of the lakes, rivers
and ponds.
Some countries drop alkalis into the lakes to neutralize the acid.

Investigating acids and alkalis

Which powder is best at neutralizing acid?
 You need to identify dependent variable, independent variable and control variable for your investigation.
 Put 20 cm3 of hydrochloric acid which has pH of 1 into each of three beakers.
 Put a few drops of universal indicator in each beaker.
 Add the three indigestion powders, A, B and C spatula by spatula, until the acid is neutralized and the
universal indicator is green.
 Record the number of spatulas used to neutralize three indigestion powders.
Here are the results

The investigation should repeat to get more reliable data.

 Finally, the conclusion is that power A is the most effective powder but powder C is the least effective.

Detecting chemical reactions

Some clues to detect the reaction has taken placed.
1. A gas is given off (formation of gas bubbles)
2. Disappearance of reactants
3. Color change
4. Heat is produced (production of heat)
5. Change in pH
6. A precipitate is formed (formation of precipitate)
 A gas (hydrogen) is
given off Metal + acid salt+
Squeaky pop test
Formation of gas hydrogen
bubbles.

A gas (carbon dioxide) When baking powder and

is given off vinegar react, carbon dioxide is
also given off. When limewater Lime water test
Formation of gas
mixes with the carbon dioxide,
bubbles.
the limewater turns cloudy.

When a piece of apple is placed Glowing splint test

in hydrogen peroxide it bubbles.
A gas (oxygen) is A gas is given off. This gas is
given off oxygen.
Formation of gas When the glowing splint is
bubbles. placed in the mouth of the test
tube, it will relight if the gas is
oxygen.

Disappearance of a reactant
When magnesium ribbon reacts with acid, hydrogen is produced and the magnesium ribbon ‘disappears’.

Color change
Gently heating black copper oxide with sulfuric acid produces a blue solution of copper sulfate.

Heat is produced
When potassium is placed in water, hydrogen gas is given off. The reaction produces so much heat the hydrogen
burns.
When you added zinc to hydrochloric acid, hydrogen gas was given off and the test tube felt hot.
Change in pH
When you neutralize an alkali, there is a change in pH.

A precipitate is formed
When the two solutions (liquids) are mixed, a solid is formed. This solid is called a precipitate.

In this reaction, silver chloride is a precipitate formed after chemical reaction.

Limewater is a solution of calcium hydroxide. The limewater turned cloudy when carbon dioxide was bubbled
into it. This is because a precipitate of calcium carbonate formed.