Goa Board Class 6 Solutions for Science – Water (English Medium)
Page No. 145:
Question 1:
Fill up the blanks in the following:
(a) The process of changing of water into its vapour is called _________________.
(b) The process of changing water vapour into water is called _________________.
(c) No rainfall for a year or more may lead to _________________ in that region.
(d) Excessive rains may cause _________________.
Solution:
(a) Evaporation
(b) Condensation
(c) Drought
(d) Floods
Concept insight: Recall water cycle in nature.
Question 2:
State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.
(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Solution:
(a) Condensation
(b) Evaporation
(c) Condensation
(d) Evaporation
(e) Evaporation
Concept insight: Recall the terms used in water cycle.
Question 3:
Which of the following statements are “true” ?
(a) Water vapour is present in air only during the monsoon. ( )
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.( )
(c) The process of water changing into its vapour, is called evaporation.( )
(d) The evaporation of water takes place only in sunlight.( )
(e) Water vapour condenses to form tiny droplets of water in the upper layers air where it is cooler.( )
Solution:
Only (c) and (e) are true.
Concept insight: Important from Exam Point of View.
Page No. 146:
Question 4:
Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Solution:
Yes, if we spread our school uniform near an anghiti or heater it will dry quickly as it will provide heat to water and it will convert into vapours quickly thus it will dry up quickly.
Concept insight: Recall the process of evaporation.
Question 5:
Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Solution:
A puddle of water is formed around a cool bottle because the water vapours near the cold bottle collide with it and lose their heat and condense.
Concept insight: Recall the process of condensation.
Question 6:
To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Solution:
During exhalation, carbon dioxide is released along with water vapours. If one breathes out, the released water vapours collide with the surface of the glass, thereby making it cooler. As a result, the water vapours present in the air surrounding the glass condense and get attached to the glass surface. Consequently, the glass becomes wet.
Concept insight: Recall the process of condensation.
Question 7:
How are clouds formed?
Solution:
As air moves up in the atmosphere, it cools down at a sufficient height. The air becomes so cool that water vapour present in it condense to form small water droplets which remain suspended in the atmosphere. These suspended water droplets appear as clouds.
Concept insight: Recall the formation of clouds.
Question 8:
When does a drought occur?
Solution:
Drought occurs when an area does not receive rainfall for a period of year or more. Due to this, soil continues to lose water by evaporation and transpiration and becomes dry.
Concept insight: What happens if it does not rain for a long period?