5. Burning may or may not be desirable change. Give reason. 6. Clothes take time drying during rainy season. Why? 7. Fermentation is an exothermic chemical change. Give reason. 8. What are the factors that affect the rate of evaporation?
Answers
Question 1.
When a woolen yarn is knitted to get a sweater, the change can be classified as _________
(a) physical change
(b) chemical change
(c) endothermic change
(d) exothermic change
Answer:
(a) physical change
Question 2.
_________ of the following are endothermic changes.
(a) Condensation and melting
(b) Condensation and freezing
(c) Evaporation and melting
(d) Evaporation and freezing
Answer:
(a) Condensation and melting
Question 3.
The chemical change is _______
(a) water to clouds
(b) growth of tree
(c) cow dung to bio-gas
(d) ice-cream to molten ice-cream
Answer:
(c) cow dung to bio-gas
Question 4.
_______ is an example of a periodic change
(a) Earthquake
(b) Formation of rainbow in sky
(c) Occurrence of tides in seas
(d) Showering of rain
Answer:
(a) Earthquake
5.chemical change is the process in which chemical composition of the substance is changed,and physical composition may or may not changed burning of coal that is carbon(C) in presence of oxygen gives a different chemical substance $$CO_2$$. So, it is a chemical change.
6.In humid weather it takes longer time to dry wet clothes because the moisture and water vapour are present in humid weather they gets slight absorbed by the clothes and clothes maintain their wetness due to this they take a longer time to dry.