1. Name the three physical states in which water exists. Give one example of water in each state from nature.
Easy(3 marks)
Solid - Ice (e.g., ice cubes, glaciers)
Liquid - Water (e.g., rivers, ponds, lakes)
Gas - Water vapour (e.g., steam, clouds)
2. Describe what happens when ice cubes are heated in a test tube until all the ice disappears. Include the names of the processes involved.
Medium(4 marks)
Ice melts to form liquid water – this process is called melting.
When heated further, liquid water turns into water vapour – this process is called evaporation.
3. Explain why water is considered an important natural resource.
Medium(3 marks)
Water is essential for all living things to survive.
It is used in daily life for drinking, cooking, cleaning, and agriculture.
It exists naturally in various forms and cycles through the environment.
4. True or False: Water vapour is the gaseous state of water.
Easy(1 mark)
True
5. List two examples each of water in the solid, liquid, and gaseous states found in nature.
Easy(3 marks)
Solid: Ice, snow, glaciers
Liquid: Rivers, lakes, ponds, wells, seas
Gas: Steam, water vapour in atmosphere
6. Describe the method and observations of the activity used to test for water vapour in the atmosphere.
Medium(4 marks)
Half-fill a glass with water and observe its outer surface after some time.
Put ice cubes into the same glass and cover with cardboard.
Observe water droplets forming on the outer surface of the glass.
This shows that water vapour in the atmosphere condenses on the cold surface.
7. Explain why water vapour can be seen on the outer surface of the glass during the activity.
Medium(3 marks)
Water vapour in the air comes into contact with the cold surface of the glass.
It cools down and changes from gas to liquid — this is condensation.
The condensed water appears as droplets on the outer surface of the glass.
8. State where glaciers are commonly found on Earth and explain their significance as a form of solid water.
Medium(4 marks)
Glaciers are found mainly in the Southern and Northern Poles of the Earth.
They are large masses of ice representing the solid state of water.
Glaciers store freshwater and slowly release it, feeding rivers and lakes.
They affect climate and sea levels.
9. Name and define the three types of water based on their availability after precipitation.
Easy(3 marks)
Precipitation: Water that falls from the atmosphere to the earth (rain, snow, hail, sleet).
Surface water: Water that remains on the surface of the earth (oceans, seas, rivers, tanks, ponds).
Ground water: Water that flows through soil and collects underground (wells, springs).
10. Describe the method and observations of the activity that tests what happens to raindrops when they fall on the soil.
Medium(4 marks)
Fill a glass tank with layers of clay, sand, stones, and gravel.
Pour water onto the layers using a tin with small holes to simulate rain.
Observe that some water flows through the layers (groundwater), some stays on the surface (surface water).
Conclusion: Rainwater can become precipitation, surface water, or groundwater.
11. Give two examples each of precipitation, surface water, and ground water.
Easy(3 marks)
Precipitation: Rain, snow
Surface water: Rivers, lakes
Ground water: Wells, springs
12. Explain why groundwater is important for human use.
Medium(3 marks)
Groundwater is a major source of fresh water for drinking and irrigation.
It is often cleaner than surface water because it is filtered by soil and rocks.
It is available year-round, even during dry seasons.
13. Define fresh water, marine water, and brackish water based on their salinity.
Easy(3 marks)
Fresh water: Water with very low salt content, found in wells, rivers, ponds.
Marine water: Water with high salt content, found in seas and oceans.
Brackish water: Water with salt content between fresh and marine water, found in lagoons.
14. In the activity using a 50 ml beaker and salt solutions, why does the mass of water increase when salt is dissolved?
Medium(3 marks)
Salt adds mass to the solution when dissolved.
The volume remains constant, but the dissolved salt increases total mass.
Therefore, salinity increases the mass of a given volume of water.
15. Explain why sea water tastes salty.
Easy(2 marks)
Sea water contains dissolved salts, mainly sodium chloride.
The dissolved salts give sea water its salty taste.
16. Design a simple experiment to compare the mass of a sample of marine or brackish water with fresh water of the same volume.
Hard(5 marks)
Take equal volumes of fresh water and marine/brackish water in separate beakers.
Use a balance to measure and record the mass of each beaker with water.
Subtract the mass of the empty beaker from each measurement.
Compare the masses: water with higher salt content will have greater mass.
Conclude that salinity affects the mass of water.
17. List five different human activities that use water, based on the examples given.
Easy(5 marks)
Drinking
Agriculture
Washing clothes
Bathing
Transportation
Generating hydroelectricity (extra)
18. Categorize the following uses of water under the correct headings: Agriculture, Bathing, Hydro electricity, Washing clothes, Transportation, Leisure activities, Sanitary purposes.
Medium(7 marks)
For industries including agriculture: Agriculture
For sanitary purposes: Bathing, Washing clothes
For household activities: Washing clothes, Bathing
For transportation: Transportation
For leisure: Leisure activities
For water related sports: Leisure activities
To generate electricity: Hydro electricity
19. Explain three ways in which water is important for the existence of life.
Medium(6 marks)
Water transports nutrients throughout the body of living organisms.
Water acts as an excretory medium to remove waste products.
Water is needed for digestion of food.
Water provides habitat for aquatic organisms.
Water helps in cooling the body through processes like sweating.
Water is essential for photosynthesis in plants.
20. What risks can a person face if they do not have enough water? Mention one example.
Easy(2 marks)
Risk of dehydration.
Example: A person suffering from diarrhea can become dehydrated and may even face death.
21. Explain why water is considered a limited natural resource even though it covers more than 70% of the earth’s surface.
Medium(4 marks)
Only about 0.01% of water on Earth is suitable for consumption.
Most water is in seas and oceans (salty) or frozen in glaciers.
Much of the fresh water sources are polluted or inaccessible.
Therefore, usable fresh water is very limited.
22. Identify three common occasions where water is wasted in homes or schools and suggest one way to minimize water wastage for each occasion.
Medium(6 marks)
Occasion: Leaving taps running – Minimize by turning taps off when not in use.
Occasion: Watering plants excessively – Minimize by watering only early morning or late evening.
Occasion: Leaking pipes – Minimize by repairing leaks promptly.
23. What is water pollution? Describe two human activities that cause water pollution.
Medium(5 marks)
Water pollution is the addition of waste materials to water bodies making them unsuitable for use.
Examples of human activities causing pollution:
Releasing waste and impure water from factories and households.
Dumping plastics and polythene into water bodies.
Using agrochemicals that run off into water.
24. Explain how water pollution affects ground water and why it is dangerous to human health.
Medium(4 marks)
Poisonous chemicals from polluted surface water seep into ground water.
Ground water is a major source of drinking water.
Contaminated ground water causes health problems like cancer and kidney failure.
Therefore, pollution of surface water endangers human health via ground water contamination.
25. Suggest two important steps individuals can take to conserve water and prevent water pollution.
Easy(3 marks)
Avoid dumping plastics and chemicals into water bodies.
Use water carefully and avoid wastage.
Participate in clean-up campaigns and spread awareness about water conservation.
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