Class 6 Science, Chapter 8 (NCERT). 15 questions by concept, 15 with pictures. Open “Show answer” for the answer and why.
How to teach this chapter · Common misconceptions & worked visual for this chapter
The arrow shows a state change. What treatment and process does it represent?
(d) heating, melting
Heat changes ice into water by melting. The arrow represents heating, melting.
The two cloths in the figure are identical and equally wet. Which cloth is expected to dry faster?
(a) the right cloth, labelled windy day
The wet cloths are the same, so compare the movement of air around them. With the increase in the movement of air, water evaporates faster. So the right cloth, labelled windy day is expected to dry faster.
Two equal amounts of water are kept in the same place with the same air movement. Use the drawing to decide which sample evaporates faster.
(c) The water in the wide shallow plate
Both samples have the same amount of water and the same surrounding conditions. The water in the wide shallow plate is spread out more, so a larger area is exposed to air. Therefore it evaporates faster.
Two identical caps contain equal amounts of water. Use the figure to see where each cap is kept. From which cap will water evaporate faster?
(d) the cap on the left
Water evaporates faster from a cap kept in sunlight compared to a cap kept in shade. The caps have equal amounts of water, so the changed condition is sunlight or shade.
A note card has a wrong sentence. Which rewrite is correct?
(b) Water vapour is invisible; tiny droplets of water in steam make it visible.
The corrected note must keep both parts of the idea. Water vapour is invisible. Tiny droplets of water in steam make steam visible.
The figure shows a student's explanation for water that disappeared from a steel plate. What is the mistake in the explanation?
(b) The mistake is saying the water seeped into the plate; it could get converted into gaseous state called water vapour.
The student's explanation says the water seeped into the plate. But the setup says water does not seep through steel. The better explanation is that water got converted into gaseous state called water vapour.
The figure shows water on a labelled surface at first and the same surface later. Which explanation best fits what happened?
(b) The water got converted into gaseous state called water vapour.
The setup says water does not seep through the utensil. The observation is that the water still disappeared. The rule is that water gets converted into gaseous state called water vapour.
The diagram ends with liquid water after condensation. What form of water belongs at the start?
(b) water vapour
Condensation changes water vapour into liquid water. Water vapour therefore belongs at the start of the arrow.
The cold tumbler develops outside droplets while its water level remains at the marked line. What source of the droplets does this evidence support?
(a) Condensation of water vapour from the surrounding air
The unchanged level supports an outside source for the droplets. Water vapour from the surrounding air condenses on the cold surface.
The droplets on the outside surface of a cold glass tumbler formed by condensation. Where was their water immediately before it condensed?
(b) As water vapour in the surrounding air
Before condensation, the water was present as water vapour in the surrounding air. Cooling changed that vapour into liquid droplets on the surface.
Ice is heated and then heated further. In the diagram, which form of water goes in the box marked ?
(d) water vapour
On heating, ice melts and gets converted into liquid water. On further heating, water gets converted into its gaseous state, water vapour. Water vapour is invisible. Steam looks white because it has tiny droplets of water in it, so steam is not the gaseous form itself. The missing box is water vapour.
Which form of water matches the behaviour shown?
(d) liquid water
Liquid water takes the container shape but keeps a definite volume. The matching form is liquid water.
Two earthen pots are placed one inside the other, with dry sand between them and a lid on top. What change makes the setup match a pot-in-pot cooler?
(b) add water in the sand area to keep the sand moist
The dry sand must be made moist by adding water in the sand area. A pot-in-pot cooler uses two earthen pots, sand, water in the sand area, and a lid or wet jute sack. Evaporation causes cooling effect, so the correction must keep the sand moist rather than relying on clay alone.
A process diagram shows air containing water vapour moving upward into cooler air. Near the top, water vapour has turned into small droplets generally around dust particles. What stage should the cloud-shaped blank marked ? be labelled?
(c) small droplets float and form clouds
The diagram has already reached the stage where water vapour in cooler air turns into droplets. The rule says these small droplets float in the air and form clouds. The blank is cloud formation, not rain or evaporation.
The diagram shows air with water vapour moving up into cooler air, and its last stage is left blank with a question mark. Starting with air becoming cooler higher above the Earth, which order correctly completes cloud formation?
(a) air becomes cooler -> water vapour turns into droplets generally around dust particles -> small droplets float and form clouds
The blank stage in the diagram is the cloud. The rule is that air containing water vapour moves higher and becomes cooler. In the cooler air, water vapour turns into droplets, generally around dust particles. These small droplets float in the air and form clouds.
Wrong
A puddle can dry only if the water boils.
Why it feels right. Both processes turn liquid into vapour, so I expect the same conditions.
Right
Evaporation can happen at the surface below the boiling point.
Worked example
