Extra Questions for Class 6 Science Chapter 6 Changes Around us
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Short Answer type questions
Question 1 VERY SHORT ANSWER TYPE QUESTION
(i)list two changes that occur without active interference of human beings.
(ii)Can you obtain wood from saw dust?
(iii)Why condensation is a physical change?
(iv)Ravi folded a sheet of paper to make a paper-boat. Comment on the nature of change that took place
(v)Name a change which occurs on heating but reversible and one which is irreversible.
Answer
(i) occurrence of day and night, growth of plant & animal body
(ii)No, because it is an irreversible change
(iii)Because no new substance is formed
(iv)It is a man-made, reversible & physical change.
(v) melting of wax
Baking of bread
Question 2 CLASSIFY THE FOLLOWING AS PHYSICAL And CHEMICAL CHANGE
(i)Pulling of iron spring
(ii)Breaking of glass beaker
(iii)Baking cake
(iv)Ploughing of field
(v)Blowing of balloon
Question 3 DEFINE THE FOLLOWING TERM
(i)Change
(ii)Exothermic reaction
(iii)Evaporation
(iv)Expansion
(v)Condensation
Answer
(i)It is an act or process through which something becomes different.
(ii)An exothermic reaction is a chemical reaction that releases energy through light or heat.
(iii)The process of turning from liquid into vapour is called Evaporation
(iv)Expansion is defined as increase in volume of a substance resulting from increase in temperature.
(v)Condensation is the process by which water vapor in the air is changed into liquid water.
Question 4 ANSWER THE FOLLOWING QUESTIONS IN BRIEF
(i)What is reversible change? give two examples
(ii)Sumita broke a vase made of Plaster of Paris. Since she knew POP is present in dust form and water is added to it to solidify it, so she made a dust of the broken pieces and mixed it water and tried to make another vase. Will she be successful? Give reason
(iii)Differentiate between physical & chemical changes.
(iv)Give four examples of irreversible change
(v)To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can it be reversed?
Answer
(i)A change which can be reversed to form the original substance by reversing the conditions that caused it, is called reversible change
E.g. – freezing of water into ice
Melting of wax
(ii)No she won’t be successful.
When POP is mixed with water then an irreversible chemical change takes place and a new substance is formed. When the vase is converter into dust it is an irreversible physical change. when the dust is mixed with water no chemical change will take place to solidify.
(iii)
Physical change
Chemical changes
The composition of the molecules remains same.
There is complete change of molecules.
No energy is generated
Energy is generated
(iv)
Burning of wood
Breaking of glass
Baking of chapati
De-forestation
(v) Yes, by unfolding the dress, the dress becomes normal. So, this Change is Reversible.
LONG ANSWER TYPE QUESTION
Question 5
(i)Name the process that leads to the formation of the second picture.
(ii)Define the above process.
(iii)Name the process which is opposite to the above process.
(iv)What will happen to the water if it is kept below 0o C?
Answer
(i)The name of the process is evaporation
(ii)Evaporation – The process of turning liquid into vapour is called evaporation.
(iii)Condensation
(iv)If water is kept below 0o C then it will freeze to ice.
Question 6
(i)What is this picture showing?
(ii)How & What kind of change takes place to form the left side of the image from the right side of the image?
(iii)What is the classification of the change?
Answer
(i)This picture shows rusted iron chain in the left and non-rusted shining iron chain in the right.
(ii)When the shining iron chain comes in contact with oxygen and moisture for long time , then a chemical change occurs on its surface and forms a layer of rust.
(iii)It is a type of irreversible chemical change.
Question 7
(i)Which of the figure is a non-periodic change? Why?
(ii)List two example of a non-periodic change.
(iii)List two examples of periodic changes.
Answer
(i)Figure A is non -periodic change. It is non-periodic because it doesn’t occur after a specific time interval.
(ii)Water freezing into ice,
Beating of heart
(iii)Changing phases of moon/change of season/clock striking an hour.
Question 8
(i)What is the above picture showing?
(ii)What is the normal size of the metal rim?
(iii)Name the process that helps the metal rim to fit on the wooden wheel.
(iv)Why & when cold water is added during the process?
Answer
(i)The above picture shows a wooden wheel and a metal rim.
(ii)The size or diameter of the metal rim is always smaller than the size of the wooden wheel.
(iii)Expansion and contraction
(iv)After heating the rim, the rim expands, once the rim is put around the wheel, then cold water is given on it. The cold-water cools down the metal rim and hence brings about a contraction & makes it tightly fit on the wheel.
