CHAPTER- 6 MATERIALS AROUND US
Notes
1. All objects are made of some kind of material, such as paper, wood, cloth, glass, metal, plastic, clay, etc.2. Material– The substance or a mixture of substances used to make an object is called material.
Question- 1. Visit your kitchen and observe how your parents have organised various edibles. Can you suggest a better sorting method? Write it in your notebook.
3. The method of organizing objects into groups is called classification.
- Objects can be divided into materials based on their similar properties.
4. Different materials can be used to make various parts of an object. For example, a pen can be made from different materials such as plastic, metal, and ink.
5. We select the material for making an object based on its properties and the purpose for which the object is to be used.
6. Lustrous– Materials whose surface is usually shiny are called lustrous.
- Shiny materials are usually metals.
- Examples– Iron, copper, etc.
7. Non-lustrous– These are materials whose surface is not shiny; they are called non-lustrous materials.
- Examples– Paper, wood, etc.
8. Not all shiny materials are metals. The surfaces of some materials are polished to make them shiny.
- Some others are coated with thin layers of plastic, wax, or other substances, which make them appear shiny.
9. Soft– Materials that can be easily pressed or scratched are considered soft.
10. Hard– Materials that are difficult to press or scratch are considered hard.
11. Transparent– Materials through which one can see clearly are called transparent. Examples: glass, water, air, etc.
12. Opaque– Materials through which one cannot see are called opaque. Examples: wood, metals, etc.
13. Translucent– Materials through which one cannot see clearly are called translucent. Examples: butter paper, frosted glass, etc.
14. Soluble– Materials that become completely invisible when mixed in water, that is, dissolve in water, are called soluble materials. Examples: sugar, salt, etc.
15. Insoluble– Materials that do not dissolve in water and do not become invisible even after prolonged stirring are called insoluble materials. Example: sand, etc.
16. Mass– Whether a material is heavy or light can be determined by measuring a property called mass, provided their volumes are the same.
- A material that is heavy has a greater mass, and a material that is light has a smaller mass.
17. Volume– The space occupied by any object represents its volume.
18. Matter– Any object that occupies space and has mass is called matter.
- Mass indicates the amount of matter and is measured in units of grams (g) and kilograms (kg).
- Volume is measured in units of liters (L) and milliliters (ml).
- In the International System of Units (SI), the kilogram is the unit of mass.
19. Just like the living world, the classification of the non-living world is also done based on their properties.
LET US ENHANCE OUR LEARNING
Answer- In my kitchen, food items are organized based on categories, such as lentils, spices, etc. I suggest that items be arranged according to their frequency of use so that everyday items are easily accessible. Using transparent containers is also a good method, as it allows the contents to be clearly visible. To identify any item, labeling it on top helps. This kind of arrangement keeps the kitchen clean, organized, and easily accessible.
Question- 2. Unscramble the letters (Column 1) and match with their properties (Column 2).
Answer-
Question- 3. The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this.
Answer- Transparent containers are used in shops and homes to store materials so that the items kept inside can be seen easily. The use of transparent containers makes it easy to know how much material is available in the container. Thus, transparent containers are useful and convenient.
Question- 4. State whether the statements given below are True (T) or False (F) correct the false statement(s).
1) Wood is translucent while glass is opaque. ( )
2) Alluminium foil has lusture while an eraser does not. ( )
3) Sugar dissolves in water whereas sawdust does not. ( )
4) An apple is a matter because it occupies no space and has mass. ( )
Answer- 1) Wood is translucent while glass is opaque. (False)
2) Alluminium foil has lusture while an eraser does not. ( )
3) Sugar dissolves in water whereas sawdust does not. ( )
4) An apple is a matter because it occupies no space and has mass. ( )
Answer- 1) Wood is translucent while glass is opaque. (False)
- Reason: Wood is opaque whereas glass is transparent.
(2) Aluminum foil is shiny while rubber is not. (True)
(3) Sugar dissolves in water, whereas sawdust does not. (True)
(4) An apple is matter because it does not occupy space and has mass. (False)
- Reason: An apple is matter because it occupies space and has mass.
Question- 5. We see chairs made up of various materials, such as wood, iron, plastic, bamboo, cement and stones. Following are some desirable properties of materials which can be used to make chairs. Which materials used to make chairs fulfil these properties the most?
1) Hardness (does not bend or shake on sitting even after long use).
2) Lightweight (easy to lift or to take from one place to another).
3) Does not feel very cold when sitting during winters.
4) Can be cleaned regularly and made to look new even after long uae.
Answer- The following materials fulfill the desirable properties for making a chair:
(1) Hardness– Wood, iron, cement, and stone are all strong and durable materials. Even after long-term use, chairs made from these materials do not bend or shake when someone sits on them.
(2) Light weight– Chairs made from wood, plastic, and bamboo are lightweight. They are easy to lift and move from one place to another.
(3) Not feeling cold when sitting in winter– Chairs made from wood and bamboo do not feel very cold when sat on during winter.
(4) Easy to clean and look like new– Chairs made from plastic, wood, and iron can be cleaned regularly and look like new even after long-term use.
Question- 6. You need to have containers for collection of: (1) Food waste, (2) broken glass and (3) waste paper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of?
Answer- The following types of containers can be selected for collecting food waste, broken glass, and waste paper:
(1) Food waste:
- Plastic or metal containers– Plastic is lightweight and easy to clean. Metal containers are strong and can help prevent odors.
- Properties: Ability to prevent odor and easy to clean.
- Metal or strong plastic containers– Metal or strong plastic containers are capable of safely holding pieces of glass and ensure that no accidents occur.
- Properties: Strong, hard, and protective against cutting or breaking.
(3) Waste paper:
- Plastic or paper containers– Plastic or thick paper containers are suitable for storing waste paper. Plastic lasts for a long time, while paper is environmentally friendly.
- Properties: Lightweight, durable, and recyclable.
Question- 7. Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in between, we cannot see each other. It is because air is ________ and the wooden door is __________. Choose the most appropriate option:
1) transparent, opaque
2) translucent, transparent
3) opaque, translucent
4) transparent, translucent
Answer- 1) transparent, opaque
Question- 8. Imagine you have two mysterious materials, X and Y, when you try to press material X, it feels rigid and does not change its shape easily. On the other hand, material Y easily changes its shape when you press it. Now, when you mix both materials in water, only material X dissolves completely, while material Y remains unchanged. What can materials X and Y be? Can you identify whether material X is hard or soft? What about material? Justify your answer.
Answer- Material ‘X’
- Hardness– This material feels hard when pressed and does not change its shape, which clearly shows that it is a hard material.
- Solubility in water– When it was mixed with water, it completely dissolved, indicating that it is soluble in water.
- Explanation– Material ‘X’ is a hard and water-soluble substance. Materials with such properties may include salt or sugar, which are solid, hard, and easily dissolve in water.
Material ‘Y’
- Flexibility– This material easily changes its shape when pressed, which shows that it is soft and flexible.
- Solubility in water– When mixed with water, it remains unchanged, which means it is insoluble in water.
- Explanation– Material ‘B’ is a soft and water-insoluble substance. Materials with such properties may include rubber or clay, which are soft or do not dissolve in water.
Therefore, material ‘X’ is hard and dissolves in water, whereas material ‘Y’ is soft and does not dissolve in water.
Question- 9. (1) Who am I? Identify me on the basis of the given properties?
(a) I have lusture. _________
(b) I can be easily compressed. __________
(c) I am hard and soluble in water. ___________
(d) You cannot see clearly through me. ___________
(e) I have mass and volume but you cannot see me. _________
(2) Make your own 'Who am I?'
Answer- (1) I am salt (sodium chloride – NaCl) because I have the following properties:
- Shiny– The crystal surface of salt is shiny.
- Easily compressible– Salt crystals are solid, but they can be crushed and ground into powder.
- Hard and water-soluble– Salt is hard and easily dissolves in water.
- Cannot see clearly through it– Salt is opaque.
- Has mass and volume– When salt dissolves in water, it becomes invisible, but its mass and volume remain.
(2) My self-made “Who am I?” riddle:
1. I am a solid, but I can melt and become a liquid when heated.
2. When light falls on my surface, I shine.
3. You can give me a shape.
4. I am a good conductor of electricity.
5. I am heavy, but strong enough to hold things.
Question- 10. You are provided with the following materials- vinegar, honey, mustard oil, water, water, glucose and wheat flour.
Make any two pairs of materials where one material is soluble in the other. Now, make two pairs of materials where one material remains in soluble in the other material.
Answer- Soluble mixtures:
Glucose + water: Glucose dissolves easily in water.
Vinegar + water: Vinegar also dissolves completely in water.
Insoluble mixtures:
Mustard oil + water: Mustard oil is insoluble in water, and the two remain in separate layers.
Wheat flour + water: Wheat flour does not dissolve completely in water; instead, it forms a paste-like mixture.
