# A Journey Through States of Water

## Overview
This chapter introduces students to the various states in which water exists—solid, liquid, and gas. Through a variety of observations and activities involving common household materials, students explore how water changes states through heating and cooling. The concepts of evaporation, condensation, freezing, melting, and the water cycle are investigated using real-life contexts.

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## Key Topics Covered

### 1. Forms of Water
- **Ice and Water Relationship**: Students learn that ice and water are different states of the same substance.
- **State Definition**: These are called physical states—solid, liquid, and gas.
- **Observation**: Ice melts into water and water can be frozen back into ice.

### 2. Disappearance of Water (Evaporation)
- **Puddle Observation**: Puddles dry up due to evaporation.
- **Everyday Examples**: Wet utensils, clothes, and sweat drying.
- **Experiment**: Water placed on steel plates does not seep through; it evaporates.
- **Conclusion**: Evaporation occurs continuously, even at room temperature.

### 3. Appearance of Droplets (Condensation)
- **Cold Glass Experiment**: Water droplets form on the outer surface of a glass of ice water.
- **Observation**: Water vapour in the air condenses on the cold surface.
- **Condensation Defined**: Conversion of water vapour to liquid.

### 4. States of Water and Their Properties
| Property | Ice (Solid) | Water (Liquid) | Water Vapour (Gas) |
|----------------------|-----------------|--------------------|----------------------|
| Shape | Fixed | Takes shape of container | No fixed shape |
| Ability to Flow | No | Yes | Yes |
| Ability to Spread | No | Yes | Yes |

- **Examples**: Ice keeps its shape, water flows and takes shape of its container, vapour spreads in the air.

### 5. Change of State
- **Heating**: Ice melts into water → water evaporates into vapour.
- **Cooling**: Water freezes into ice.
- **Other Examples**: Wax, coconut oil, and ghee also change states based on temperature.
- **Definitions**:
- *Melting*: Solid to liquid.
- *Freezing*: Liquid to solid.
- *Evaporation*: Liquid to gas.
- *Condensation*: Gas to liquid.

### 6. Conditions Affecting Evaporation
- **Surface Area**: Water in a plate evaporates faster than in a bottle cap due to larger surface area.
- **Sunlight vs. Shade**: Water evaporates faster in sunlight.
- **Air Movement**: Wind speeds up evaporation (clothes dry faster on windy days).
- **Humidity**: On humid or rainy days, evaporation is slower because air already contains water vapour.

### 7. Cooling Effect of Evaporation
- **Earthen Pot Example**: Water stays cooler in a clay pot due to evaporation through tiny pores.
- **Hand Sanitiser**: Rubbing alcohol evaporates quickly and cools your hands.
- **Activity**: Pot-in-pot cooler demonstrates electricity-free refrigeration.

### 8. Formation of Rain (Water Cycle)
- **Process**:
1. **Evaporation** from oceans, lakes, rivers.
2. **Condensation** into clouds as water vapour cools.
3. **Precipitation** as rain, snow, or hail when droplets combine and fall.
- **Role of Dust Particles**: Help form clouds as condensation happens around them.

### 9. The Water Cycle
- A continuous process where water moves between surface and atmosphere.
- Involves **evaporation**, **condensation**, **precipitation**, and **collection**.
- Important for maintaining Earth's water balance.

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## New Terms and Simple Definitions

| Term | Definition |
|---------------|------------|
| Evaporation | Changing of water into vapour. |
| Condensation | Changing of vapour into liquid. |
| Melting | Changing of solid into liquid. |
| Freezing | Changing of liquid into solid. |
| Water Vapour | Water in gas form. |
| Humidity | Water vapour present in the air. |
| Water Cycle | Continuous movement of water on Earth. |
| Cooling Effect| Lowering of temperature due to evaporation. |

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## Practice Questions

### Easy (3)
1. What is the solid state of water called?
**Answer**: Ice
**Explanation**: Ice is frozen water, a solid form.

2. Name the process by which water turns into vapour.
**Answer**: Evaporation
**Explanation**: Heat turns water into gas.

3. Why do we feel cool after using sanitiser?
**Answer**: Because of evaporation
**Explanation**: It evaporates quickly and absorbs heat.

### Medium (2)
4. What is condensation? Give one example.
**Answer**: Conversion of vapour into water; Example – Water droplets on a cold glass.
**Explanation**: Air's moisture cools and turns to liquid.

5. Why do clothes dry faster on a windy day?
**Answer**: Due to increased evaporation from moving air.
**Explanation**: Wind removes water vapour faster from wet clothes.

### Difficult (3)
6. Explain how the water cycle works in your own words.
**Answer**: Water evaporates, forms clouds by condensation, and falls back as rain.
**Explanation**: It repeats and keeps water moving on Earth.

7. What role do dust particles play in cloud formation?
**Answer**: They help water vapour condense.
**Explanation**: Water needs a surface to form droplets.

8. Why does water from an earthen pot feel cooler than from a steel pot?
**Answer**: Because of evaporation from the pot surface.
**Explanation**: Water seeps and evaporates, taking heat away.

### Very Difficult (2)
9. If a glass of ice water is left on a table, water forms on the outside. Explain why.
**Answer**: Due to condensation of water vapour from air.
**Explanation**: Vapour cools down and turns to liquid.

10. Design an activity to test how temperature affects evaporation.
**Answer**: Use 2 plates of water—keep one in sun and one in shade. Measure evaporation time.
**Explanation**: Higher temperature leads to faster evaporation.

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