Photosynthesis

Photosynthesis is the use of light with the help of a chemical called chlorophyll together with Carbon
dioxide to make sugars (food) in plants and Oxygen is given off.

How does photosynthesis occur?

Plants use chlorophyll, sunlight, water and carbon dioxide to make food.
1. Chlorophyll captures the sunlight energy.
2. This energy split the water into hydrogen and oxygen.
3. The oxygen is released into the air.
4. The hydrogen is used with the carbon dioxide to make glucose (sugars).
5. The sugars are moved from the leaves to other parts of the plants where they are stored.
6. The water in the plant veins carries the sugars. When the sugars reach the storage parts, they are
changed into starch.

Plants can store the starch in these places:

  Leaves (cabbage, spinach, lettuce)
  Fruit (apples, banana, peaches)
  Stems (sugar cane)
  Seeds (wheat or mealies)
  Flowers (broccoli and cauliflower)
  Roots (carrots or beetroot)

Plants store food as starch

Plants make more glucose than they need so the plant change some of the glucose sugar in their leaves
into starch. The starch is the food that the plant keeps in reserve. Plants store the starch in their leaves,
stems, roots, flowers, fruits and seeds. There is a lot of starch in potatoes, maize and grains like wheat.

Testing foods for starch

We will experiment to find out which foods contain starch. Iodine solution can be used to test for starch.
Starch turns brown iodine solution to a blue black colour.

Why do plants need fertiliser?

Plants need some nutrients that they cannot make themselves. The most important of these
are nitrogen, potassium and phosphorus. Plants get these nutrients from the soil. The nutrients dissolve in
the water and plants absorb the water and the nutrients through their roots.

Plants and Air

Plants keep the amount of carbon dioxide and oxygen in the Earth’s atmosphere constant. During
photosynthesis plants use carbon dioxide from the air and give off oxygen into the air.
All living organisms use the oxygen to breathe. We breathe out carbon dioxide into the air. Plants absorb
this carbon dioxide for photosynthesis.
Some differences between respiration and photosynthesis
Respiration Photosynthesis
It only takes place in cells that have
chlorophyll.
It takes place in all living plant cells.
Chlorophyll gives the cells a green colour.

It occurs in light and dark conditions. It only occurs in light.

Oxygen is used and carbon dioxide and water Carbon Dioxide and water are used and
are released. Oxygen is released.

How does this help human beings?

Humans cannot produce oxygen and will die without it. Carbon Dioxide is a harmful gas that, can kill human
beings. Respiration uses only a little oxygen and releases very little carbon dioxide. Photosynthesis uses a
lot of carbon dioxide and releases a lot of oxygen. The relationship between these two processes means
that plants create more oxygen than they use and use more carbon dioxide than they release which helps
human beings.

Nutrients in food: Food groups

There are seven life processes that every living thing needs: energy to feed, breathe, move,
grow, excrete, sense things and to reproduce.

The four main food groups are:

  Carbohydrates – for energy
  Proteins – for growth and repair
  Fats and oils – for storing energy and insulation
  Vitamins and minerals – for building bones and teeth and maintaining a healthy
immune system.

Carbohydrates
Carbohydrates give living organisms energy. Carbohydrates are used by the body to keep
it warm and to provide all the energy it needs for growth and movement. Without
carbohydrates, you will be too tired to walk, run, and dance or even to think. Carbohydrate
foods contain sugars and starch. We find sugary carbohydrates in fruits, honey, dried fruits,
cold drinks, etc. Sugar gives our body’s quick energy. Sugary foods do not have all the important nutrients
in them that our bodies need. We find starch in foods such as maize meal, potatoes, rice, bread, pasta and
some fruits. Starch releases energy more slowly into our bodies so the energy lasts longer. Starch is the
most common form of carbohydrate in our diet.

Proteins
Living things need proteins to build and repair their bodies and for growth. Proteins also helps us fight
sicknesses and they help the immune system fight off infections. Proteins also make up part of the red
blood cells, which is vital for carrying oxygen from the lungs to the rest of the body. Muscles and organs are
mostly made up of proteins. Proteins make everything in the human body, such as bones, hair, skin and
nails. It is important to get proteins from a variety of foods such as meat, fish, eggs, nuts, and beans. Eating
the right amount of protein is important to help repair any tissues that are damaged through normal use
over the years. Proteins give the body strength and is essential for muscle growth.

Oils and fats

Oils and fats provide energy to living organisms. Oils and fats give more energy than any other food type.
They store energy in the form of body fat. These body fats form protective layers inside the body, to protect
the organs and provide insulation (keep heat in). Foods such as nuts, avocado pears and sardines contain
healthy oils and fats. Oils are liquid fats made from plants and fish and they provide important nutrients.

Vitamins and minerals

Vitamins and minerals work together with carbohydrates, proteins and fats to help our bodies grow and
develop normally. Our bodies need vitamins and minerals to help us build strong teeth and bones, have
good eyesight and a healthy immune system. The immune system fights germs and stops us from getting
sick.

Food additives
Most food that comes in a package such as a tin, bottle, box or sealed plastic packet, is processed food.
Most processed or manufactured foods have added salt (sodium) and sugar as well as other food additives
such as preservatives, flavourants and colorants.
  Flavourants – and MSG (flavour enhancer) which improve the taste
  Preservatives – (sodium nitrite and sodium nitrate) makes food last longer
  Colorants – makes food look appetizing or good enough to eat.

What are E numbers?

E numbers are codes for chemicals that can be used as food additives.
Many food additives have E numbers.
E 100 – 199 are colorants
E 200 – 299 are preservatives
E 600 – 699 are flavouring

Nutrition
Healthy eating
The selection of foods you eat every day makes up your diet. A balanced diet contains enough food from all
four food groups, as well as water and fibre, to keep you healthy. We need to eat the correct amounts of
carbohydrates, proteins, fats, vitamins and minerals.

Water and fibre

Fruits and vegetables are also high in fibre. Fibre is the part of plant food that you cannot digest, but it is
good for your digestive system. Grains like oats and whole wheat are also high in fibre. It prevents you from
suffering from constipation and can protect you from diabetes or heart problems.
Junk food and fast food
Junk food is food that is high in sugar, high in fat and high in salt.

Fast food
Fast food is fried food or takeaway food. It is quickly prepared (often pre-prepared) and
highly processed. Examples of fast food are French fries (potato chips), pies, hot dogs, burgers, fried
chicken and pizzas.

The Traffic Light Diet

Red: stop and think twice
Eat these foods only in small amounts. These foods include junk food and fast foods. They include: -
Sweets, hamburgers, chips and fizzy drinks.

Orange: be careful/ pause

Eat a little bit of these foods every day. These foods include fat or sugar-rich foods like: - Butter, eggs,
cheese, bacon and red meat

Green: go for it
Add plenty of fresh fruits and vegetables to your diet. These foods include: - Fish, milk and yogurt, whole-
wheat bread, fresh fruits and vegetables.

Diseases related to diet

What you eat is important for your health, especially as you grow older. Some diseases are the result of a
poor diet. Other diseases can be managed by a good diet.

Tooth decay
Tooth decay is caused by bacteria (germs) that feed on sugars on your teeth. The bacteria make acids that
cause holes (cavities) in your teeth. If you eat a lot of sugary food, then you increase your chances of tooth
decay.

Diabetes
Diabetes is a condition of high blood sugar. Some people are born with diabetes. Type 2 diabetes can be
caused by eating too many sugary foods and drinking too many fizzy sweet drinks. People with diabetes
have to be very careful about what they eat. They have to inject themselves with insulin in order to keep
their blood sugar levels correct.

Obesity
Obesity is the condition of being unhealthily overweight. It is caused by eating too much food (especially
food high in sugars and fats) as well as doing too little exercise.
Obesity can lead to disease like:
  Diabetes (often caused by eating too much sugar)
  Heart disease (often caused by eating too much fat)
  Hypertension or high blood pressure
Food processing
Food processing is the process of turning raw plant and animal materials into food products.
We buy them from supermarkets and it comes in a box. This food is preserved. Consumers want safe,
nutritious, convenient and inexpensive food throughout the year.
Food is processed for the following reasons:
  To make it edible and ready to eat, or quick and easy to prepare.
  To make it last longer
  To improve its nutrient value
  Food is processed for our eating convenience

Fortified foods are foods that have had vitamins and minerals added to them to raise or restore their
nutrient content.

Methods for food processing

Three food products:
Preparing, combining and cooking are three ways of processing food.
  Preparing involves processes such as shelling, peeling, slicing or chopping.
  Combining is the mixing of two or more ingredients.
  Cooking involves heat. It includes methods such as boiling, baking, steaming, roasting and frying.

Ways of preserving food.

Food does not last long before going rotten. It goes stale, or it spoils as moulds and bacteria
start to grow on it and break it down. Food is often processed to preserve it, or make it last longer.
 Heating (cooking) kills bacteria.
 Freezing, pickling, drying or salting (adding lots of salt) stops bacteria from growing on the food.
 Pickling is the process of preserving food in salt water or vinegar. (Salt water is called
brine)
Fermenting
Fermenting is a method of food processing that uses yeast or bacteria. The yeasts or bacteria multiply as
they feed on the food and change the starches or sugars into acids or alcohol. Fermenting improves the
nutritional value of the food or beverage. The yeasts or bacteria themselves are nutritious and they partly
digest the food. Yoghurt, amazi, ginger beer and sorghum beer are all made using the fermentation
process.
Drying food
Drying(water is removed) completely changes the taste and texture of food. For example, dried fruit is
smaller than fresh fruit and tastes sweeter. When water is removed, micro-organisms are unable to grow.
Some types of dried food need to have water added again before you can eat them, for example pasta or
noodles.
Ecosystems
Habitat - home of plant or animal
Biodiversity - different types of plants and animals
Indigenous - plants or animals that always lived there
Shelter - place that gives protection from outside
Interdependence - when living and non-living things need each other to live
Ecosystem - different habitats all over the world
In South Africa there are indigenous biodiversity and they have special features to survive in their habitats.
Animals live in different places in order to get food, water, air and shelter.
Herbivores - eat plants
Carnivores - eat animals
Omnivores - eat animals and plants
Scavengers - feed off dead animals and plants
Decomposers - eat and break up dead animals and put chemicals back into the soil.
Food webs
Producer - plants make (produce) their own food
Energy flow - Energy that is passed on from one animal to another
Consumer - animals that can not make their own food
Food Chain - order in which animals eat plants and animals
Term 2: Matter and Materials Grade 6 (NST)
Introduction
Solids, liquids and gases are the three main states of matter. Materials and substances are made
of matter. Matter is made of particles. The way the particles are arranged makes the matter a
solid, a liquid or a gas. Matter is made of very small particles.

A particle is the smallest part of a substance.

Particles move. Particles move all the time. Sometimes they move slowly, sometimes they move
fast. The speed and distance they move in determines if the material or substance is a solid, a
liquid or a gas.

Solids
When matter is solid, it has a fixed shape. The particles of solids are packed closely together.
There is very little space between the particles. The particles vibrate or move in one place. Eg.
Coin.

Liquids
Matter in the liquid state is able to flow. The substance will take on the shape of the container it is
in. The particles are packed close together, but they have no fixed shape. There are small spaces
between the particles. The particles can move around each other.

Gas
When matter is in the gas state, it fills the available space around it. The particles in gas are far
apart from each other and move fast. There is a lot of space between the particles. The particles
move in all directions.

Mixture: Mixtures of Materials

When two or more different substances (or materials) are combined, the result is a mixture. The
substances or materials can be in the solid, liquid or gas state.

Separating Mixtures
There are many different ways to separate mixtures so that the materials are visible again. It is
easier to separate substances we can see. We can physically separate these substances by
sieving, filtering, hand sorting, settling or decanting.

Method 1: Sorting by hand

Pouring the mixture onto newspaper or a piece of plastic
Using your fingers or a pair of tweezers
Picking out one of the materials from the others

Method 2: Using a sieve

Pouring the mixture through a sieve into a bowl
Shaking the sieve so that the small materials fall through
The larger material will remain in the sieve.

Method 3: Settling and decanting

Stirring the mixture
Leaving the mixture in its container
Allowing the mixture to stand until the two materials separate
Carefully pouring off the top material from the other material

Method 4: Filtering
Placing a funnel in a bottle
Placing filter paper in the funnel
Pouring the mixture through the funnel
Allowing the liquid material to flow through the filter

Solutions as Special Mixtures: Solutions

A solution is a special mixture of a liquid and a solid. Solutions are uniform in appearance

Dissolving a solid
Dissolving is the process of mixing a solid and a liquid so that the solid is no longer visible. If the
solid dissolves in the liquid, it is said to be soluble. If it does not dissolve, it is insoluble.

Dissolving uses mixing to combine a solid and a liquid.

Melting uses heat to convert one solid into a liquid.

Dissolving a solid: Solutes and Solvent

Solids that can dissolve are called solutes. The liquid in which a solute dissolves is called the
solvent. Water is a unique solvent as so many substances can dissolve in it.

The making of Sea Salt

Salt from the land has washed into the sea. The salt has dissolved in the sea and tastes salty. The
seawater is the solvent. The salt is the solute. The solution is the mixture of the salt and water.

Solutions as Special Mixtures: Saturated Solutions

When substances dissolve, solute particles become dispersed in the spaces between the solvent
particles. When the spaces are full, there is nowhere else for the solute to go. The solute particles
that are left out can be seen in the solvent.
Saturated – when a solution has no more space for any more particles of the solute.

Solutions as Special Mixtures: Insoluble Substances

Water is known as a universal solvent. Many different substances can dissolve in water and
makes water very useful. Substances that do not dissolve in water are insoluble. Oil is insoluble in
water. Oil and water do not mix and oil will float on water.

Insoluble Substances as Water Pollution

Oil and sand are only two of many substances that are insoluble in water. Waste such as plastic
bags, tins and bottles are all insoluble. They pollute our rivers and seas.

Dissolving: Rates of Dissolving

The speed at which a solute dissolves is called the rate of dissolving

There are three factors that affect the rate of dissolving:

Temperature of mixtures
Substances will dissolve faster in warmer water than in colder water. In warm water, there are
more spaces between the particles of water.

Stirring versus shaking the mixture

Stirring and shaking are both ways of mixing a solute with a solvent. Stirring is better at mixing the
solute with the solvent than shaking the solution.

Grain size of the solute

A large grain of solute will take longer to dissolve than a small grain. The larger the grain, the
slower the rate of dissolving will be.

Mixtures and Water Resources: Water Pollution

All water eventually runs into a river somewhere. If it is polluted water, it will carry the pollution to
the river. When pollution mixes with water it can dissolve and form a solution of solutes and
solvents which is poisonous to organisms in the water. Some pollution is insoluble but still mixes
with the water but is seen on the surface.

Insoluble Substances
Insoluble substances cannot dissolve in water and are harmless. Things like oil, plastic, tyres, tins,
glass and sewage waste are bad for the water and people using the water.

Oil Pollution
Oil can also pollute large amounts of water. Oil spreads as a thin layer on top of water. The oil kills
wildlife and plants that depend on the river. Oils make the water undrinkable and it is impossible to
remove.

Preventing Water Pollution

 Never throw waste into a river or on the ground.
 Never pour oil down a drain sink.
 Most insoluble items can be removed from a river by hand.
 Organised river clean-ups can remove many insoluble pollutants from our rivers.

Soluble Substances
Soluble substances dissolve in water. This means it is very difficult to know if they are in water or
not. They are virtually impossible to remove and cause pollution, which then makes the water
undrinkable.

Examples of soluble pollution are:

 Fertilisers and insecticides used by farmers
 Chemicals used by factories
 Soap powder used for washing clothes
 Soap used by people to wash themselves

Impact of Fertilisers on Rivers

The effect of these pollutants is to poison the water so that nothing can live in it we call this
eutrophication. Eutrophication is when small plants called algae feed of the fertilisers, soaps and
even some chemicals. The algae grow very fast and turn the rivers and lakes green. The water
cannot be used for drinking. Some algae secrete poisons that make the water poisonous.

Preventing Water Pollution:

 Use as little soap and detergents as possible.
 Use as little fertiliser as possible in your garden.
 Avoid using pesticides and herbicides in the garden.
Living Germs
Germs are living creatures that cannot be seen with the naked eye. Even clean looking water can
have germs. Germs cause diseases and cause people to become ill. The most common illness
carried by water is diarrhoea. The sewage from people is washed into rivers. People drink the
water and become ill. This forms a cycle of infection.
To avoid contracting diseases that are transported in water…
 Do not play in or drink polluted water
 Wash your hands with soap before eating
 Report broken toilets

Mixtures and Water Resources: Importance of Wetlands

A wetland is shallow body of water with plants such as reeds. Other names for wetlands are
marshes, swamps, seepage areas and food-plains. The water in a wetland can be salty or fresh
water. The slow flowing water allows insoluble substances to settle. Sand and silt sink to the
bottom of the wetland. The water becomes clear. Plants absorb nutrients from the water. Water
may become drinkable after flowing through a wetland.

Process to Purify Water: Clean Water

Animals and water
All animals would eventually dehydrate without water. Not only does water keep an animal cool
but water is also needed to digest food and remove waste. Without clean water, people would also
not be able to grow food, keep clean or be healthy.

Plants and Water

Plants need the nutrients that are dissolved in water. The waste contains nutrients that the plants
can use. The plants absorb the nutrients through their roots and the nutrients are used to make
food for the plants.

The Importance of clean water

Water management is everyone’s responsibility but the municipality officials of towns and cities
have the responsibility of looking after the water treatment facilities. The municipality must purify
water to keep people healthy.
M 2022
How a water treatment facility works
Water treatment plants are places where water from dams, rivers and aquifers are cleaned. To
clean the water the following steps are taken:
 Water is pumped to the water treatment plant.
 Water is filtered through a sieve.
 Water is then filtered through a very fine material called a membrane.
 A chemical called chlorine is added to kill any germs.
 Other chemicals are added to remove any bad tastes or smells.
 The water is pumped to factories and houses.
There are four ways to purify water:
Boiling Water
Boiled water is heated to kill any germs in the water.

Filtering Water
Pouring water through a funnel and filter paper removes most of the insoluble pollution.

Settling Water
Water that is allowed to settle will appear to be clean but not all the insoluble pollutants will settle.

Chemical Treatment
Chemicals or iodine added to water to kill germs but they are expensive and water taste awful.
1. Use the words in the blocks below to complete the sentences.

a. A plant makes food in it’s ___________ through the process of ______________.

b. A plant uses the energy in ___________ as well as _____________ and

____________ to make ___________ which can be changed into _____________

and stored. c. A plant gives off ____________ into the air. This is used by people and animals.

2. What is photosynthesis?
3. Where does photosynthesis in the plant mainly take place?
4. Explain why it takes place there.
5. Name three things that plants need from their environment for photosynthesis to take place.
6. As what do plants store their food?

Activity 2
1. Why is it useful to know which foods contain starch?
2. Name one advantage of eating foods that contain starch.
3. Does bread contain starch? Give a reason to support your answer.
4. What substance is used to test for starch?
5. Why is this substance used for a starch investigation?
1. How many servings of these foods did Nadiema have?
a. Grains group
b. Dairy group
c. Meat, fish and beans
d. Vegetables and fruits
e. Fats and oils.
2. Was Nadiema’s diet balanced on this day? Give a reason for your answer.
3. List the foods that she should eat:
a. More of
b. Less of
Read the case study and answer the following questions about Natalie’s diet.

Natalie’s diet
Natalie is a 12-year-old girl and she is in Grade 6.
This is what she ate yesterday. It is similar to what she eats every day.
Do you think that she is eating a balanced diet?
Activity 1 - term 2
Questions
Identify the type of matter represented by:
1. Standing close together.
2. Spread out holding hands.
3. Running around each other.