Air and Water
1. Air Is Everywhere
AIR is all around us. It is INVISIBLE but we can FEEL it.
'Close your eyes and take a deep breath. Can you feel the air entering your NOSE? Now hold your breath — see how your body NEEDS air!'
Where Is Air?
- In the ROOM around you.
- In the SOIL (worms need it).
- In WATER (fish breathe dissolved air).
- In a BALLOON (blow it up!).
2. Properties of Air
| Property | How to See It |
|---|---|
| Air takes up SPACE | Blow up a balloon — air fills it |
| Air has WEIGHT | A blown balloon weighs more than an empty one |
| Air is INVISIBLE | You cannot see it, but you can feel it |
| Air has PRESSURE | When you suck on a straw, air pressure pushes the drink up |
| Air can be COMPRESSED | Push the plunger of a syringe with the tip closed |
| Air is needed for BURNING | Cover a candle with a glass — it goes out |
| Air is needed for BREATHING | We breathe in oxygen from air |
3. Moving Air — Wind
WIND is AIR that is MOVING.
'On a still day, the air feels CALM. On a windy day, you can FEEL the air rushing past you!'
Effects of Wind:
| Gentle Wind (Breeze) | Strong Wind (Storm) |
|---|---|
| Leaves rustle | Trees bend |
| You feel cool | You can be pushed |
| Kites fly easily | Roofs can be damaged |
| Smoke drifts | Dust storms |
Uses of Wind:
- Drying CLOTHES.
- Flying KITES.
- Windmills make ELECTRICITY (wind energy).
- Sailing BOATS.
4. Sources of Water
Water is found in MANY places on Earth.
| Source | Description | Type of Water |
|---|---|---|
| RAIN | Water falls from clouds | Fresh |
| RIVERS | Flowing water from mountains to sea | Fresh |
| LAKES | Large bodies of water surrounded by land | Fresh |
| PONDS | Small bodies of still water | Fresh |
| WELLS | Water from underground | Fresh |
| TAP WATER | Treated water supplied to homes | Fresh |
| OCEANS | Very large saltwater bodies | SALTY |
| GLACIERS | Frozen water on mountains | Fresh |
5. The Water Cycle
The WATER CYCLE is how water moves from the Earth to the sky and back again.
'Water is NEVER lost. It keeps going around and around in a never-ending CYCLE.'
Step 1 — Evaporation:
The SUN heats water in oceans, rivers, and lakes. Water turns into WATER VAPOUR (a gas) and rises into the air.
'Think of puddles DISAPPEARING after rain. Where does the water go? It EVAPORATES into the air!'
Step 2 — Condensation:
Water vapour rises high in the sky where it is COLD. It turns back into tiny WATER DROPLETS. These droplets form CLOUDS.
'Have you seen water droplets on the OUTSIDE of a cold glass? That is CONDENSATION!'
Step 3 — Precipitation:
When the clouds get HEAVY with water droplets, the water falls back to Earth as RAIN (or snow/hail if it is very cold).
Step 4 — Collection:
The rainwater COLLECTS in rivers, lakes, and oceans. Some soaks into the ground. And the cycle STARTS AGAIN!
6. Water Conservation
Water is PRECIOUS. We must not WASTE it.
'Only about 1% of Earth's water is FRESH water that we can drink. We must use it CAREFULLY!'
How to Save Water:
| Do This | Don't Do This |
|---|---|
| Close the tap while brushing | Let the tap run while brushing |
| Take SHORT showers | Take long showers |
| Use a BUCKET to wash | Use a hose to wash |
| Fix LEAKING taps | Ignore dripping taps |
| Water plants in the MORNING | Water plants at noon (water evaporates!) |
| Collect RAINWATER | Let rainwater go to waste |
7. Common Mistakes
- Thinking air is nothing: 'Air IS something — it is a mixture of gases. It has weight and takes up space.'
- Believing the water cycle creates NEW water: 'NO new water is created. The SAME water has been cycling for millions of years!'
- Confusing evaporation and condensation: 'Evaporation is liquid → gas (water → water vapour). Condensation is gas → liquid (water vapour → water droplets).'
- Thinking only oceans have water: 'Water is found in rivers, lakes, ponds, wells, glaciers, and even underground. But most of Earth's water is in the OCEANS.'
8. Key Facts to Remember
- 'Air is EVERYWHERE — it is invisible but takes up space and has weight.'
- 'Wind is MOVING air.'
- 'Water comes from RAIN, RIVERS, LAKES, PONDS, WELLS, and OCEANS.'
- 'The WATER CYCLE has 4 steps: Evaporation, Condensation, Precipitation, Collection.'
- 'We must CONSERVE water — do not waste it.'
- 'Air is needed for BREATHING and BURNING.'
9. Self-Test
Q1: How can you prove that air takes up space?
Q2: What is wind?
Q3: Name the four steps of the water cycle.
Q4: What is evaporation? Give an example.
Q5: What is the difference between evaporation and condensation?
Q6: Name three sources of fresh water.
Q7: Why should we save water?
Q8: Why does a candle go out when covered with a glass?
Answers:
A1: Blow up a balloon — the air fills it and makes it expand. The air is taking up space inside. A2: Wind is MOVING AIR. A3: (1) Evaporation (2) Condensation (3) Precipitation (4) Collection. A4: Evaporation is liquid water turning into water VAPOUR (gas) by HEAT. Example: a puddle drying up in the sun. A5: Evaporation = liquid → gas (heating). Condensation = gas → liquid (cooling). A6: Rivers, lakes, ponds, wells, rain, glaciers (any three). A7: Only about 1% of Earth's water is fresh and drinkable. Water is limited. We need it for drinking, cooking, and farming. A8: The candle uses up the OXYGEN inside the glass. Without oxygen, the flame goes out.
