Matter and Materials — Class 5 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 5 Science, Unit 2. Matter, the manufacture of fabrics, grains and food products, and floating and sinking. Taught in June and July.
1. What matter is
Matter is anything that has mass and occupies space.
Both parts of that sentence matter. A stone has mass and takes up room. So does the air in a balloon, even though you cannot see it.
Matter exists in three states:
| State | Particles | Shape | Volume |
|---|---|---|---|
| Solid | Tightly packed, cannot move freely | Definite | Definite |
| Liquid | Loosely packed, can slide past each other | Takes the container's shape | Definite |
| Gas | Far apart, move freely | No fixed shape | No fixed volume; compressible |
Stone, wood and a book are solids. Water, milk and oil are liquids. Air, oxygen and steam are gases.
2. Fibres: where cloth begins
The cloth you are wearing began as a fibre. Fibres are either natural or synthetic.
Natural fibres come from plants or animals:
- From plants: cotton (from the cotton ball), jute (from the stem), coir (from the coconut husk)
- From animals: wool (from sheep and goats), silk (from the silkworm's cocoon)
Synthetic fibres are man-made: nylon, polyester, acrylic. Rayon is made from wood pulp.
Silk is an animal fibre, not a plant one. The silkworm is an insect, and it spins the thread itself.
3. Cotton, and how it becomes cloth
A cotton plant is a bushy plant about 5 to 6 feet high. It grows well in black soil and alluvial soil — which is why cotton does well across much of India.
The plant bears many small green pods called cotton balls, and inside each are seeds and fibres.
Turning those fibres into fabric takes four steps in a fixed order:
| Step | What happens |
|---|---|
| Ginning | The raw fibres are separated from the seeds. What is left is called lint |
| Spinning | The lint is tied, pressed and drawn out into yarn |
| Weaving or knitting | Yarn is turned into fabric |
So the chain runs: cotton balls → cotton fibre → ginning → lint → spinning → yarn → weaving → fabric.
Ginning and spinning are easy to confuse. Ginning comes first and separates seeds from fibre. Spinning comes second and makes yarn from fibre.
4. Jute, the golden fibre
Jute fibre is obtained from the stem of the jute plant, not from a pod. The plant has long, soft and shiny fibres.
Jute is known as the golden fibre, because of its colour and because it is cheap.
The fibres are separated by retting — soaking the cut stems in water for several days so the bark loosens — after which they are dried by hand and spun into yarn in the same way as cotton.
5. Grains
A grain is a small, hard, dry seed. Each grain is protected by a husk, which encloses the seed.
Commercial grain crops are of two main types: cereals and legumes. Wheat, maize, rice, beans, peas, barley and millets are all whole grains.
Wheat is the most important crop in the world.
Rice is a type of grass. It is cultivated worldwide after sugarcane and maize, and it is the main food of a large part of the world's population, especially in Asia. Ninety per cent of the world's rice production is in Asia.
There is a nutritional point here worth knowing. White rice contains few essential nutrients, because the outer layers are polished away. Brown rice is a whole grain and keeps them.
6. Floating and sinking
Some objects float in water and others sink. What decides it is density.
When an object is put into a liquid, the liquid pushes up on it. That upward force is called upthrust.
If the upthrust is enough to balance the object's weight, the object floats. A heavy iron nail sinks; a much heavier wooden log floats, because what matters is not weight alone but how much mass is packed into the space the object occupies.
7. Liquids of different densities
Liquids have densities too. Try to mix two liquids of different densities and they separate as soon as you stop stirring: the heavier liquid settles at the bottom and the lighter one floats on top.
Pour oil into water and the oil sits above, because oil is less dense than water.
8. Mixing and dissolving
Some substances dissolve completely in water. We say these are soluble, and the clear result is a solution. Salt and sugar are soluble.
Others do not dissolve at all. Take five test tubes half filled with water and add a spoonful each of coconut oil, kerosene, mustard oil, lemon juice and vinegar. Stir, then let them stand. Lemon juice and vinegar mix with the water. The oils and kerosene do not — they separate and float on top.
9. Worked examples
Example 1. Define matter.
Solution: Anything that has mass and occupies space.
Example 2. Which process separates cotton fibres from their seeds?
Solution: Ginning. The fibrous material left over is lint.
Example 3. From which part of the plant is jute obtained, and why is it called the golden fibre?
Solution: From the stem. It is called the golden fibre because of its colour and its cost effectiveness.
Example 4. True or false: coir is the outer covering of coconut.
Solution: True.
Example 5. True or false: cotton balls contain jute fibre.
Solution: False. Cotton balls contain cotton seeds and cotton fibres.
Example 6. What decides whether an object floats or sinks?
Solution: Its density, together with the upthrust the liquid exerts on it.
Example 7. Why does brown rice have more nutrients than white rice?
Solution: Brown rice is a whole grain and keeps its outer layers, while polishing removes them to make white rice.
10. Practice
- What is matter? Give one example of each state.
- Name two plant fibres and two animal fibres.
- In what soil does the cotton plant grow well, and how tall is it?
- What is lint?
- Put these in order: spinning, weaving, ginning.
- What is the process of separating jute fibres from the stem called?
- What are the two main types of commercial grain crops?
- What fraction of the world's rice is produced in Asia?
- What is upthrust?
- If two liquids of different densities are mixed and left to stand, which one settles at the bottom?
11. Answers
- Anything that has mass and occupies space. Solid: stone. Liquid: water. Gas: air.
- Plant fibres: cotton and jute (also coir). Animal fibres: wool and silk.
- In black soil and alluvial soil. It is a bushy plant about 5 to 6 feet high.
- The fibrous material left after the cotton seeds have been separated.
- Ginning, then spinning, then weaving.
- Retting.
- Cereals and legumes.
- Ninety per cent.
- The upward force a liquid exerts on an object immersed in it.
- The heavier, denser liquid.
12. Summary
- Matter is anything that has mass and occupies space, and exists as solid, liquid or gas.
- Natural fibres come from plants (cotton, jute, coir) or animals (wool, silk); rayon comes from wood pulp.
- The cotton plant is bushy, 5 to 6 feet tall, and grows well in black and alluvial soil.
- Cotton becomes cloth by ginning, then spinning into yarn, then weaving or knitting.
- Ginning separates seed from fibre and leaves lint; spinning makes yarn.
- Jute comes from the stem, is separated by retting, and is called the golden fibre.
- A grain is a small hard dry seed enclosed in a husk; cereals and legumes are the two main crops.
- Wheat is the world's most important crop; 90 per cent of the world's rice is grown in Asia.
- Brown rice is a whole grain and keeps nutrients that polishing removes from white rice.
- Density decides floating and sinking, and upthrust is the liquid's upward push.
- Denser liquids settle below lighter ones; soluble substances dissolve completely in water.
