50 Very Short Answer Type Questions — Topic-wise

Concise answers follow each question for rapid revision and memorization.

1. 1. What are the three main states of water?Solid (ice), liquid (water), and gas (water vapour).
2. 2. What is melting?Melting is the change of a solid into a liquid on heating.
3. 3. At what temperature does pure water melt?Pure water melts at 0 °C under normal atmospheric pressure.
4. 4. What is freezing?Freezing is the change of a liquid into a solid on cooling.
5. 5. At what temperature does pure water boil?Pure water boils at 100 °C at 1 atmosphere pressure.
6. 6. What is evaporation?Evaporation is the change of liquid into vapour from the surface at any temperature.
7. 7. How is evaporation different from boiling?Evaporation occurs at the surface at any temperature; boiling occurs throughout the liquid at its boiling point.
8. 8. What is condensation?Condensation is the change of vapour into liquid when cooled.
9. 9. What is precipitation?Precipitation is water falling from clouds as rain, snow or hail.
10. 10. Define sublimation.Sublimation is when a solid changes directly into gas without becoming liquid.
11. 11. Give one example of sublimation.Dry ice (solid CO₂) changing directly into gas is an example of sublimation.
12. 12. Why does ice float on water?Ice is less dense than liquid water due to its crystal structure, so it floats.
13. 13. What is the water cycle?The water cycle describes evaporation → condensation → precipitation → collection of water on Earth.
14. 14. What causes clouds to form?Clouds form when water vapour cools and condenses into tiny droplets around dust particles.
15. 15. What is transpiration?Transpiration is the release of water vapour from plant leaves into the atmosphere.
16. 16. Why do puddles dry faster on a sunny day?Higher temperature and sunlight increase evaporation, making puddles dry faster.
17. 17. What is latent heat?Latent heat is the energy absorbed or released during a change of state without temperature change.
18. 18. During melting, does temperature increase?No — temperature remains constant during melting while latent heat is absorbed.
19. 19. Name two factors that increase evaporation.Higher temperature and increased surface area (and airflow) increase evaporation.
20. 20. What is dew?Dew is water droplets formed by condensation on cool surfaces, usually in the morning.
21. 21. Why does steam condense on a cold lid?Cold surface cools the vapour, causing water vapour to condense into droplets on the lid.
22. 22. What is fog?Fog is a cloud near the ground formed by condensation of water vapour in the air.
23. 23. How does salt affect the freezing point of water?Salt lowers the freezing point of water, causing ice to melt at lower temperatures.
24. 24. What is meant by collection in the water cycle?Collection is water gathering in rivers, lakes and oceans after precipitation.
25. 25. What role does the Sun play in the water cycle?The Sun provides energy for evaporation, driving the water cycle.
26. 26. What is the difference between steam and water vapour?Steam is visible droplets formed when vapour condenses; water vapour is the invisible gaseous form of water.
27. 27. Why is evaporation a cooling process?Evaporation requires energy that is taken from the surroundings, causing cooling.
28. 28. Give an everyday example of condensation.Water droplets on the outside of a cold glass are an example of condensation.
29. 29. What is rain?Rain is liquid precipitation formed when cloud droplets combine and fall to the ground.
30. 30. What is hail?Hail is frozen precipitation formed in strong thunderstorms as ice pellets grow and fall.
31. 31. How does pressure affect boiling point?Lower atmospheric pressure (higher altitude) lowers the boiling point; higher pressure raises it.
32. 32. What is meant by water vapour?Water vapour is the gaseous form of water that is invisible in air.
33. 33. Why are polar regions covered with ice?Low temperatures in polar regions cause water to remain frozen as ice and snow.
34. 34. What is meant by the term 'precipitation'?Precipitation includes all forms of water falling from clouds: rain, snow, sleet, and hail.
35. 35. How does vegetation affect the water cycle?Vegetation adds water vapour to the air via transpiration and helps retain soil moisture, affecting local cycles.
36. 36. What is an example of a reversible change involving water?Melting ice to water and then freezing it back is a reversible physical change.
37. 37. Why is water called the universal solvent?Water dissolves many substances due to its polar nature, making it a universal solvent.
38. 38. What causes clouds to become heavy and produce rain?Cloud droplets combine and grow larger until they are heavy enough to fall as rain.
39. 39. Give one way humans impact the water cycle.Deforestation reduces transpiration; urbanisation increases runoff and reduces infiltration.
40. 40. What is the role of condensation nuclei in cloud formation?Condensation nuclei (dust or salt particles) provide surfaces for water vapour to condense into droplets.
41. 41. How does evaporation help in cooling clothes?Evaporation of water from wet clothes removes heat, cooling the fabric and helping it dry.
42. 42. What is the difference between snow and sleet?Snow falls as ice crystals; sleet is small pellets of ice formed when raindrops freeze before reaching the ground.
43. 43. Why is steam sometimes dangerous?Steam can cause severe burns because it carries latent heat and releases energy upon condensing on skin.
44. 44. What is ground water?Ground water is water stored under the Earth's surface in soil and rock pores.
45. 45. How do clouds help regulate Earth's temperature?Clouds reflect sunlight (cooling) and trap heat at night (warming), affecting Earth's temperature balance.
46. 46. What is meant by 'runoff' in the water cycle?Runoff is water flow on land that moves into rivers and lakes after rainfall.
47. 47. How does boiling differ from evaporation in terms of particle movement?During boiling, particles throughout the liquid gain enough energy to form vapour; evaporation involves surface particles escaping into vapour.
48. 48. Name one experiment to show evaporation.Place equal water samples in sun and shade and observe the faster water loss in sunlight.
49. 49. What is the effect of impurities on melting point?Impurities usually lower or broaden the melting point range of a substance (e.g., salt lowers ice's melting point).
50. 50. Why is understanding the water cycle important?It explains weather, water availability, and helps manage water resources for agriculture and society.