Materials Around Us Class 6 Questions and Answers

Question 1.
Would it be a good idea to use paper-like materials for making cooking utensils? (Page 104)
Answer:
No. Paper-like materials are not suitable for making cooking utensils. Such materials cannot withstand high temperature of the flame and may burn. The liquid contents of the food will also soak the paper.

Question 2.
Are all lustrous materials metals? (Page 107)
Answer:
All lustrous materials may not be metals. Somei materials can be made lustrous by polishing or coating them with a thin layer of plastic, wax or any other material which makes them look shiny.

Question 3.
Is water transparent? Can it be made opaque? (Page 110)
Answer:
Pure water is transparent. It can be made opaque by adding some other materials to it. For example, muddy water is opaque.

Question 4.
Does everything you put in water disappear? (Page 111)
Answer:
No. Everything we put in water does not disappear. Only the materials which are soluble in water disappear when mixed with water in limited amount.

Question 5.
Are there any properties which can be shown by all materials? If yes, what are those? (Page 115)
Answer:
Yes, there are some properties which are shown by all materials. All material objects possess mass and occupy space.

Let Us Enhance Our Learning (pages 119-121)

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.
Answer:
Pulses such as moong dal, chana dal, urad dal, arhar dal, etc., should be grouped together. Cereals such as rice, dalia, wheat flour, maize flour, etc., should be grouped together.
Spices such as red chilli powder, salt, clove, black pepper, ajwain, cumin (jeera), coriander seeds (dhaniya), turmeric powder, garam masala etc., should be grouped together.
Cooking oils and ghee such as mustard oil, soyabean oil, olive oil, cow ghee, etc., should be grouped together.
Jams and squashes should be placed together.

Question 2.
Unscramble the letters (Column I) and match with their properties (Column II).

Answer:

Column I	Column II
(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.

Question 3.
The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this.
Answer:
The containers which are used to store materials in shops and at home are usually transparent so that the materials stored in them can be seen through them and can be found easily.

Question 4.
State whether the statements given below are True [T] or False [F], Correct the False statements).
(i) Wood is translucent while glass is opaque.
Answer:
False
Wood is opaque while glass is transparent.

(ii) Aluminium foil has lustre while an eraser does not.
Answer:
True

(iii) Sugar dissolves in water whereas sawdust does not.
Answer:
True

(iv) An apple is a matter because it occupies no space and has mass.
Answer:
False
An apple is a 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 fulfill 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) Iron, cement and stones
(ii) Plastic and bamboo
(in) Wood and bamboo
(iv) Plastic, iron, cement and stones

Question 6.
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:
We can use plastic containers for collection of (i) food waste (ii) broken glass and (iii) waste paper. These containers may have different colours because food waste is biodegradable, broken glass is hazardous and waste paper is recyclable. In case of food waste, the material of the container should not react with food and should be leak proof. For broken glass the material of the container should be hard so that glass should not cut it. For storing waste paper the material of the container should be light and strong.

Question 7.
Air is all around us but does not hinder u‘s 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:
(i) transparent, opaque
(ii) translucent, transparent
(iii) opaque, translucent
(iv) transparent, translucent
Answer:
(i) 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 shapk 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:
X can be sugar crystal and Y can be rubber block.
The material X is hard.
The material Y is soft.

Question 9.
(i) 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.

(ii) Make your own Who am I?’
Answer:
(i) (a) steel
(b) rubber
(c) sugar
(d) cardboard or plywood
(e) air

(ii) (a) You can see clearly through me
(b) I am soft
(c) I am non-lustrous
(d) I am liquid and insoluble in water
(e) I cannot be compressed easily.

Question 10.
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:
Soluble pairs
(i) Water and glucose
(ii) Water and vinegar

Insoluble pairs
(i) Water and mustard oil
(ii) Water and wheat flour

Activities

Activity 6.1: Let us Identify (Page 102)
Make a list of objects you see around and also write the names of the materials they are made up of in Table.

Answer:
Table: Identify materials

I Observe (Objects)	Materials they are made up of
1. Books	Paper
2. Table	Wood
3. Tumbler	Glass
4. Notebook	Paper
5. Pen	Plastic, metal and ink
6. Pencil	Wood and carbon (graphite)
7. Scale	Plastic
8. Sharpener	Plastic and metal
9. Chair	Wood
10. Shirt	Cloth and plastic (buttons)

Activity 6.3: Let us think (Page 104)
Let us think what materials we can use to make a tumbler. Fill in the names of the materials in the spaces provided in Fig. 6.2. (See Textbook, Page 104)

Answer:
To study the various materials that can be used to make a tumbler
The material selected for making an object depends on the properties of material and the purpose for which the object is to be used. We may use different materials for making an object. The materials that are required to make a tumbler should be capable of holding water or some other beverage which is put into it. We cannot use cloth for making a tumbler because water would leak through it.

It may be concluded that material use a for making tumbler should be able to hold the liquid substance such as milk, water, tea, etc., in the tumbler. The porous materials such as cloth cannot be used for making tumbler because it will not be able to hold the liquid.

Activity 6.4: Let us Explore (Page 105)
Fig. illustrates a variety of balls that are of the same size but made up of different materials.

Different types of balls used for various purposes

• Take each ball and drop it from a fixed height.
• Note the height to which the ball bounces and record.
• Identify the ball that achieves the highest bounce.

Answer:
To explore the bouncing level of the balls used for various purposes
Balls used for different purposes are made up of different materials. Bouncing levels of these balls are different.

• Take different balls that are of the same size but made up of different materials.
• Take each ball and drop it from a fixed height (about 2 m).
• Observe the height to which the ball bounces and record it.
• Identify the ball that achieves the highest and the lowest bounce.

Table: Bouncing level of the balls

Ball	Bounce (high, medium or low)
Tennis ball	High
Cricket ball	Low
Hand exercise ball	Medium
Any other	Medium

It is observed that balls made up of different materials bounce back to different levels. The cricket ball has low bouncing level whereas hand exercise ball has high bouncing level. Bouncing level of tennis ball is medium.
It may be concluded that a level to which the ball bounces back depends upon the type of material used for making it.

Activity 6.5: Let us Observe (Page 107)
Hold the objects given in Table 6.3 with your hands. Feel whether the objects are hard or soft. Find out the materials they are made up of. Enter your observations in Table 6.3.

Compare your observations with the observations of your friends and discuss.
Answer:
To study whether the given objects are hard or soft and to find the materials the objects are made up of Materials which can be compressed or scratched easily are classified as soft, while the materials which are difficult to compress or scratch are classified as hard.

Table: Classification of objects as hard or soft and study of materials they are made u of

Objects	Hard/soft	Materials
1. Brick	Hard	Baked clay
2. Water bottle	Hard	Plastic
3. Pillow	Soft	Cloth and cotton
4. Tumbler	Hard	Glass
5. Table	Hard	Wood
6. Sweater	Soft	Wool
7. Spoon	Hard	Steel
8. Pen	Hard	Plastic, metal and ink
9. Hand exercise ball	Soft	Rubber

From the above observations it may be concluded that an object may be hard or soft depending on the nature of the material it is made up of.

Activity 6.6: Let us Classify (Page 109)

Classify the following objects as transparent, translucent or opaque in Table.

Table: Classification of Objects

Answer:
The materials through which the things can be seen clearly are called transparent.
The materials through which we are not able to see at all are called opaque. The materials through which the objects can be seen, but not clearly are called translucent.
Record the results in tabular form.

Transparent	Translucent	Opaque
Glass tumbler	Butter paper	Eraser
Window glass	Frosted glass	Wooden board

NCERT Solutions for Class 6 Science Chapter 6 Changes Around Us

Topics and Sub Topics in Class 6 Science Chapter 6 Changes Around Us

Section Name	Topic Name
6	Changes Around us
6.1	Can all changes always be reversed?
6.2	Could there be other ways to bring a change?

Class 6 Science Chapter 6 Textbook Questions Solved

1. To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Ans: Yes, it can be reversed by unfolding the dress.

2. You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
Ans: No, this change (breaking of toy) cannot be reversed.

3. Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.

4. A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Ans: No, we cannot get fresh drawing sheet once a picture is drawn on it with paint/ oil or water. However, we can reverse the change, if soft pencil is used to draw the picture.

5. Give examples to explain the difference between changes that can or cannot be reversed.
Ans: Examples of reversible and irreversible changes

6. A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed?
Ans: No, the change in POP cannot be reversed since it is a chemical change.

7. A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Ans. No, these are irreversible chemical changes.

EXTRA QUESTIONS for Class 6 Science Chapter 6

Class 6 Science Chapter 6 VERY SHORT ANSWER TYPE QUESTIONS

1. Give two examples of slow changes.
Ans:
(a) Growing of plants
(b) Ripening of fruits.

2. Give two examples of fast changes.
Ans:
(a) Blowing of balloon
(b) Rolling out roti from dough ball.

3. Give two examples of reversible changes.
Ans:
(a) Drying of wet clothes
(b) Heating of milk.

4: Give two examples of irreversible changes.
Ans:
(a) Milk to cheese
(b) Cooking of food.

5. Can you say deforestation is an irreversible or reversible change?
Ans: It is an irreversible change.

6. Does the size of the paper change after making an aeroplane by folding it or by cutting it?
Ans: Yes.

7. Can you change the shape of a eraser after erasing?
Ans: Yes.

8. Why does a blacksmith heat the metal rim to fix it on a cart wheel?
Ans: A blacksmith heats the metal rim to fix it onto a cart wheel because a metal rim is made slightly smaller. On heating, the rim expands and fits onto the wheel. Then on cooling, the rim contracts and fits tightly onto the wheel.

9. What are slow and fast changes? Give examples.
Ans: The changes which take place in a long period of time are called slow changes whereas that changes which take place in a short period of time are called fast changes.
Examples:
(a) Rusting of iron, formation of day and night, ripening of fruits, growing of trees are slow changes.
(b) Burning of paper, stretching of rubber band, blowing of balloons, bursting of crackers are fast changes.

10. Classify the following into slow and fast changes:
(i) Spinning of top
(ii) Formation of day and night
(iii) Formation of curd from milk
(iv) Change of season
(v) Making curd from milk by adding lemon juice.
Ans:
(i) Fast change
(ii) Slow change
(iii) Slow change
(iv) Slow change
(v) Fast change.

11. Classify the following as slow or fast change:
(i) Bearing of heart
(ii) Change of seasons
(iii) Burning of paper
(iv) Weathering of rocks
(v) Melting of wax
(vi) Cooking of food
(vii) Burning of wax
(viii) Melting of ice cream
(ix) Curding of milk
(x) Formation of day and night
Ans:
(i) Fast
(ii) Slow
(iii) Fast
(iv) Slow
(v) Fast
(vi) Slow
(vii) Fast
(viii) Fast
(ix) Slow
(x) Slow

12. Write some changes happening in our body.
Ans:
(a) Our nails grow
(b) Our hair grows
(c) We grow taller
(d) Our weight increases.

 13. Some common changes are given in Table 6.1. Which of these changes do you think can be reversed?

Class 6 Science Chapter 6 SHORT ANSWER TYPE QUESTIONS

1. What is a physical change? Explain with example.
Ans: The changes in which only physical properties of substances are changed and no new substance is formed is called physical change. It is a reversible change. Example: Boiling and freezing of water.

2. What is a chemical change? Explain with example.
Ans: The changes in which new substance with new chemical properties are formed are called chemical changes.
Example: Reaction between washing soda and lemon juice in which C02 and other substances are formed.

3. What happens when sugar is heated?
Ans: When sugar is heated continuously then a black powdery substance is formed. This is a chemical change.

Class 6 Science Chapter 6 LONG ANSWER TYPE QUESTIONS

1. Explain how a metal rim slightly smaller than a wooden wheel can be fixed on it.
Ans: The metal rim is always made slightly smaller than the wooden wheel. The metal rim is heated. On heating, the rim expands and fit onto the wheel. Cold water is then poured over the rim. Due to cooling the metal rim contracts and fits tightly onto the wheel.

2. How does curd being set? Is this change reversible?
Ans: A small quantity of curd is added to warm milk. The milk is stirred and is set aside undisturbed for a few hours at a warm place. In a few hours, the milk changes into curd.
Curd formed from milk cannot be changed into milk again. So, this an irreversible (cannot be reversed) change.

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