**Three States of Water:**
1. Solid (ice) — hard, cannot flow, keeps shape
2. Liquid (water) — flows, takes shape of container
3. Gas (water vapour/steam) — invisible, spreads in air
**Key Processes:**
**Evaporation** = Water → Water Vapour (happens at room temperature, visible as disappearance)
**Condensation** = Water Vapour → Water Droplets (happens on cold surfaces)
**Melting** = Ice → Water (heat causes it)
**Freezing** = Water → Ice (cold causes it)
**Important Points:**
**Diagrams to Remember:** Melting cycle (ice ↔ water ↔ vapour), cold glass tumbler with droplets, puddle disappearing, dew drops on grass
**Don't Confuse:** Evaporation (liquid to gas) ≠ Seeping (water soaks into ground). Condensation (gas to liquid) ≠ Freezing (liquid to solid). Steam (visible) ≠ Water Vapour (invisible).
Q1. What happens to an ice cube when left on a table at room temperature?
Answer: A — Heat from room temperature causes ice to melt and convert into liquid water.
Q2. Which of the following is an example of evaporation?
Answer: C — Evaporation is when water converts into water vapour and disappears; wet clothes drying is a clear example.
Q3. The process of conversion of water vapour into liquid water is called _________.
Answer: C — Condensation is when water vapour (gas) converts into liquid water droplets on cold surfaces.
Q4. Why do water droplets appear on the outside of a cold glass tumbler containing ice water?
Answer: C — The cold glass surface causes water vapour in the surrounding air to condense into visible water droplets.
Q5. Which of the following statements is true?
Answer: B — Ice and water are the same substance (H₂O) but in different physical states — ice is solid, water is liquid.
Q6. Dew drops on grass in the early morning are formed due to _________.
Answer: C — At night, water vapour in the cool air condenses on cold grass leaves forming dew drops.
Q7. What is the main difference between steam and water vapour?
Answer: B — Water vapour is pure invisible gas, while steam is water vapour mixed with tiny visible water droplets.
Q8. If you sprinkle water on a hot dosa pan, the water quickly disappears. This process is called _________.
Answer: C — The heat from the hot pan causes water to rapidly evaporate and convert into invisible water vapour.
Q9. Water puddles disappear from the playground after rain mainly because of _________.
Answer: C — Puddle water both evaporates into the air as water vapour and seeps into the soil below.
Q10. When water boils in a covered pot and water droplets appear on the inner side of the lid, this demonstrates _________.
Answer: C — Water evaporates from the boiling liquid, and the water vapour condenses back into droplets on the cold lid surface.
What happens to ice when left at room temperature?
Ice melts and converts into water.
Define evaporation.
Evaporation is the process where water converts into its invisible gaseous state called water vapour.
Why do wet clothes dry when hung on a rope?
Water in wet clothes evaporates and becomes invisible water vapour in the air.
What is water vapour?
Water vapour is the invisible gaseous state of water formed when liquid water evaporates.
Define condensation.
Condensation is the process where water vapour in air converts into liquid water droplets when it touches a cold surface.
Why do water droplets appear on the outside of a cold glass tumbler with ice?
Water vapour in the air condenses into liquid water droplets when it comes in contact with the cold glass surface.
Give one example of evaporation from daily life.
Water disappearing from puddles after rain, or sweat drying from our skin, or mopped floor drying.
What is the difference between steam and water vapour?
Steam is visible because it contains tiny water droplets, while water vapour is invisible pure gas.
Does evaporation happen only on hot days?
No, evaporation happens continuously even at room temperature, though it happens faster on hot days.
Where do dew drops come from on plants in the morning?
Water vapour in the cool night air condenses on the cold plant leaves forming dew drops.
What are the three states of water? [1 mark]
Name the three physical forms of water: one solid (freezing temperature), one liquid (room temperature), one gas (high temperature). Example from puddle activity.
Explain the difference between evaporation and condensation with one example each from your daily life. [2 marks]
Evaporation = liquid to gas (example: drying of wet clothes). Condensation = gas to liquid (example: water droplets on cold glass). Use the words 'water' and 'water vapour' in your answer.
Why do we see water droplets on the outside of a glass tumbler containing cold water and ice cubes? Explain the process with a reason. [3 marks]
The process is condensation. Water vapour from the air comes in contact with the cold glass surface and converts into liquid water droplets. Connect this to the concept that water vapour is always present in air but is invisible until it condenses.
Describe Activity 8.2 (steel plate with water) and explain what conclusion you draw from it. Draw and label a diagram showing the disappearance of water from the steel plate. [5 marks]
Activity: place water on steel plate, observe, water disappears. Conclusion: water does NOT seep through the steel plate; instead it evaporates and becomes water vapour (invisible gas). Diagram: Show steel plate with water at Day 1, partially disappeared at Day 2, completely gone at Day 3, with arrow showing 'evaporation' or 'water vapour rising into air'.
True or False: Ice and water are different substances. Give one reason to support your answer. [2 marks]
False. Ice and water are the same substance (water/H₂O) in different states. When ice is heated, it melts into water. This proves they are the same substance, just in different physical forms (solid and liquid).
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