Visit your kitchen and observe how your parents have organised various edibles. Can you suggest a better sorting method? Write it in your notebook.
Answer
In most kitchens, edibles are kept together based on a common property, for example, all spices in one place, all pulses and grains in another, and so on. This way of arranging things into groups based on a common property is called classification.
A better sorting method could be to group the edibles according to how they are used or how often they are needed. For example:
- Daily-use items such as tea, sugar, salt and cooking oil can be kept together near the cooking area.
- Pulses and grains can be stored together in airtight containers.
- Spices can be kept in a separate spice box.
- Items that spoil quickly, such as milk and vegetables, can be kept in the refrigerator.
This makes it easy to find and pick out the required item quickly.
Unscramble the letters (Column I) and match with their properties (Column II).
| Column I | Column II |
|---|---|
| (i) T R E M A T | (a) Objects can be seen clearly through it |
| (ii) U L S B E L O | (b) Occupies space and has mass |
| (iii) T N E R P A S N A R T | (c) Shiny surface |
| (iv) E R U S T L | (d) Mixes completely in water |
Answer
| Unscrambled word | Property |
|---|---|
| (i) MATTER | (b) Occupies space and has mass |
| (ii) SOLUBLE | (d) Mixes completely in water |
| (iii) TRANSPARENT | (a) Objects can be seen clearly through it |
| (iv) LUSTRE | (c) Shiny surface |
The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this.
Answer
Transparent materials are those through which things can be seen clearly. The containers used to store materials are usually transparent so that the material kept inside them can be seen clearly from outside without opening the container. This helps us to know what is stored inside and how much of it is left, making it easy to find and use the required material.
State whether the statements given below are True [T] or False [F]. Correct the False statement(s).
(i) Wood is translucent while glass is opaque.
(ii) Aluminium foil has lustre while an eraser does not.
(iii) Sugar dissolves in water whereas sawdust does not.
(iv) An apple is a matter because it occupies no space and has mass.
Answer
(i) False
Corrected Statement — Wood is opaque while glass is transparent.
(ii) True
(iii) True
(iv) False
Corrected Statement — An apple is a matter because it occupies space and has mass.
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?
(i) Hardness (does not bend or shake on sitting even after long use).
(ii) Lightweight (easy to lift or to take from one place to another).
(iii) Does not feel very cold when sitting during winters.
(iv) Can be cleaned regularly and made to look new even after long use.
Answer
(i) Hardness — Wood, iron and stone are hard materials. They can be used to make strong, durable chairs when properly designed and constructed.
(ii) Lightweight — Plastic and bamboo are lightweight materials, so chairs made of them are easy to lift and carry from one place to another.
(iii) Does not feel very cold when sitting during winters — Wood, plastic and bamboo do not feel very cold, so chairs made of these are comfortable to sit on during winters.
(iv) Can be cleaned regularly and made to look new — Plastic chairs are easy to clean, and painted or coated iron chairs can also be cleaned regularly and maintained in good condition.
You need to have containers for collection of: (i) food waste, (ii) broken glass and (iii) wastepaper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of?
Answer
(i) Food waste — A container made of plastic or metal should be chosen because food waste is wet. The material should not allow water to pass through and should be easy to clean.
(ii) Broken glass — A container made of metal or thick, hard plastic should be chosen. The material should be hard and strong so that the sharp pieces of glass cannot pierce or tear it.
(iii) Wastepaper — A container made of cardboard or plastic should be chosen because paper waste is light and dry. The material should be lightweight and easy to carry.
While choosing the containers, we should consider the hardness and strength of the material, its resistance to water and how easy the container is to clean and carry.
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:
- transparent, opaque
- translucent, transparent
- opaque, translucent
- transparent, translucent
Answer
transparent, opaque
Reason — Air is transparent, so we can see clearly through it and are able to see each other. Wood is opaque, so we cannot see through it. Therefore, a wooden door in between prevents us from seeing each other.
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 Y? Justify your answer.
Answer
Material X can be sugar crystals or rock salt. It is hard because it does not change shape easily when pressed, and it is soluble because it dissolves in water.
Material Y can be soft rubber, such as the rubber used to make a soft eraser. It is soft because it changes shape when pressed, and it is insoluble because it does not dissolve in water.
Hence, material X is hard and soluble in water, whereas material Y is soft and insoluble in water.
Who am I? Identify me on the basis of the given properties.
(a) I have lustre.
(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.
Answer
(a) A metal (such as iron, copper or aluminium) — metals have lustre.
(b) A soft material (such as a sponge or cotton) — it can be easily compressed.
(c) Sugar (or salt) — it is hard and dissolves completely in water.
(d) A translucent material (such as butter paper or frosted glass) — things cannot be seen clearly through it.
(e) Air — it has mass and volume but cannot be seen.
Make your own 'Who am I?'
Answer
Sample 'Who am I?'
I am a transparent material. You can see clearly through me. I break easily when dropped. I am used to make window panes and tumblers. Who am I?
(Answer: Glass)
You are provided with the following materials—vinegar, honey, mustard oil, 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 insoluble in the other material.
Answer
Pairs where one material is soluble in the other:
(i) Glucose and water — glucose dissolves completely in water.
(ii) Vinegar and water — vinegar mixes completely with water.
Pairs where one material remains insoluble in the other:
(i) Mustard oil and water — mustard oil does not mix with water and forms a separate layer.
(ii) Wheat flour and water — wheat flour does not dissolve in water and remains insoluble.