A Journey through States of Water

Given: An ice cube is left in a cup at room temperature.

Observation: The ice cube gradually melts and turns into water (liquid).

Conclusion: Ice and water are the same substance. Ice is the solid state of water, and when heat from the surroundings is absorbed by the ice, it melts and becomes liquid water. Both ice and water are made of the same substance — they are simply two different states of water.

- Water flows but ice does not.
- Water splashes but ice does not.

These differences in behaviour are due to the different states (solid and liquid) of the same substance.

Yes, water in puddles does disappear over time. It disappears due to two main reasons:

1. Evaporation: Water on the surface of the puddle absorbs heat from the sun and surroundings, converts into water vapour, and mixes with the air. This is the primary reason.
2. Seeping into the ground: Some water may seep through the soil into the ground (especially if the ground is not paved).

Therefore, water from puddles disappears mainly due to evaporation and partly due to seeping into the ground.

Examples of water disappearing:

1. Wet clothes dry after some time when hung out.
2. Water on a mopped floor dries up.
3. Sweat on our body dries up.
4. Water left on utensils after washing dries up.
5. Water sprinkled on a hot pan disappears instantly.

Reason: In all these cases, water undergoes evaporation — it absorbs heat from the surroundings and converts into water vapour, which mixes with the air and becomes invisible. This is why water seems to 'disappear'.

Activity Design (Activity 8.2):

Materials needed: A steel plate, a tablespoon of water.

Steps:
1. Place a steel plate on a flat surface.
2. Put a tablespoon of water on the top surface of the steel plate.
3. Observe whether any water appears on the underside (bottom surface) of the plate.
4. Keep observing at regular intervals until the water on top completely disappears.

Expected Observation: No water appears on the underside of the steel plate. The water on top gradually disappears without seeping through.

Inference: Water does not seep through the steel plate. Therefore, Thirav is correct. The water disappears because it converts into water vapour through the process of evaporation, not because it seeps through the plate.

Answer: The water that was placed on the steel plate has been converted into its gaseous state, called water vapour.

- The process by which water converts into water vapour is called evaporation.
- Evaporation takes place continuously, even at room temperature.
- The water vapour mixes with the surrounding air and becomes invisible, which is why it appears that the water has 'disappeared'.

Examples of evaporation in daily life:
- Drying of wet clothes
- Drying of a mopped floor
- Evaporation of sweat from our body

Answer: (iii) Both seeping of water into the ground AND evaporation of water.

Explanation:
- Evaporation: The sun heats the water in the puddle, causing it to convert into water vapour and mix with the air. This is the major reason for water disappearing from puddles.
- Seeping into the ground: If the ground is made of soil (not paved), some water also seeps through the soil into the ground.

Therefore, both processes contribute to the disappearance of water from puddles, with evaporation being the more significant factor.

Answer: When we rub hand sanitiser on our hands, it evaporates rapidly.

Reason:
- Hand sanitiser contains alcohol (like ethanol or isopropanol), which evaporates much faster than water.
- The friction from rubbing and the warmth of our hands provides the heat needed for evaporation.
- As the sanitiser evaporates, it takes heat from our hands, which is why we feel a cooling sensation when we apply sanitiser.

This is the same process as evaporation of water, but it happens much more quickly because alcohol evaporates faster than water.

Observation: No water appears on the underside of the steel plate. The water on the top surface gradually disappears over time.

Inference: Water does not seep through the steel plate. The water disappears because it evaporates — it converts into water vapour and mixes with the air.

Is this activity enough? Yes, this activity is sufficient to conclude that water does not seep through a steel plate, because:
- If water had seeped through, we would see water droplets on the underside of the plate.
- Since no water appears on the underside, and the water on top disappears, it confirms that the water has evaporated, not seeped through.

However, to be more thorough, we could repeat the activity multiple times and with different amounts of water to confirm the conclusion.

Observation: Water droplets appear on the outer surface of the glass tumbler containing cold water and ice cubes.

Possible Reasons:

1. Condensation of water vapour (Most likely reason): The air around us contains water vapour. When this water vapour comes in contact with the cold outer surface of the glass tumbler, it loses heat and converts into liquid water droplets. This process is called condensation.

2. Seeping of water through the glass: Water might be seeping through the walls of the glass tumbler from inside to outside. (This can be tested by Activity 8.4.)

Evidence for Condensation:
- We observe dew drops on plants in the morning — this is also due to condensation of water vapour on the cool surface of leaves.
- When we boil water in a covered utensil, water drops form on the inner side of the lid — this is also condensation.

Conclusion: The most likely reason is condensation of water vapour present in the surrounding air on the cold outer surface of the glass tumbler.

Answer: We see dew drops more in the morning because:

1. During the night, the temperature drops significantly.
2. The surfaces of plants, grass, and other objects become very cold.
3. The water vapour present in the air comes in contact with these cold surfaces.
4. This water vapour condenses (converts from gaseous state to liquid state) and forms tiny water droplets called dew drops.
5. In the morning, before the sun heats up the surfaces, these dew drops are still visible.
6. As the day progresses and the sun heats up the surfaces, the dew drops evaporate and disappear.

Therefore, dew drops are seen more in the morning because the surfaces are coldest at that time, favouring condensation.

Answer: The water drops on the inner side of the steel plate come from the condensation of steam (water vapour).

Explanation:
1. When water is boiled, it converts into steam (water vapour).
2. This steam rises upward and comes in contact with the steel plate covering the utensil.
3. The steel plate is cooler than the steam.
4. When the hot water vapour touches the cool steel plate, it loses heat and condenses — converting back into liquid water droplets.
5. These water droplets accumulate on the inner side of the steel plate.

This is the same process of condensation — the conversion of water vapour into its liquid state upon contact with a cool surface.

Table 8.1: Observations and Questions

| I observe | I wonder |
|---|---|
| Water droplets appear on the outer surface of the glass tumbler. | Where do these water droplets come from? |
| The outer surface of the glass feels wet and cold to touch. | Is the water seeping through the glass from inside? |
| Initially small droplets form, then they combine to form bigger drops. | Is the water coming from the air around the glass? |
| The glass tumbler feels very cold on the outside. | Why does the outside of the glass become cold? |

Inference: The water droplets on the outer surface of the glass tumbler are formed due to condensation of water vapour present in the surrounding air. The cold surface of the glass causes the water vapour in the air to cool down and convert into liquid water droplets.

Prediction: The mass of the cold water (glass tumbler with cold water and ice cubes) kept on the digital weighing balance will increase.

Reason:
- The cold surface of the glass tumbler causes the water vapour present in the surrounding air to condense on its outer surface.
- This condensed water (from the air) gets deposited on the outer surface of the glass tumbler.
- Since extra water from the air is being added to the outer surface of the glass, the total mass of the system increases.

Conclusion from Activity 8.4: The increase in mass confirms that:
1. Water is not seeping from inside the glass to the outside (if it were, the mass would remain the same).
2. Extra water from the surrounding air is condensing on the cold outer surface of the glass.
3. This proves that the water droplets on the outer surface are due to condensation of water vapour from the air.

Table 8.3: Comparison of Different States of Water

| Property | Ice (Solid state) | Water (Liquid state) | Water vapour (Gaseous state) |
|---|---|---|---|
| Shape | Has a definite, fixed shape. Does not change shape when transferred to another container. | Has no fixed shape. Takes the shape of the container it is poured into. | Has no fixed shape. Spreads in all directions and fills the entire space available. |
| Ability to flow | Cannot flow. It is rigid and stays in one place. | Can flow easily from one place to another. Flows from higher level to lower level. | Can flow (move) in all directions. Spreads throughout the available space. |
| Ability to spread | Does not spread. Stays in its original form. | Spreads on a flat surface but stays on the surface. | Spreads in all directions and fills the entire container or space. |

Summary:
- Solid (Ice): Fixed shape, cannot flow, does not spread.
- Liquid (Water): No fixed shape, flows easily, spreads on surfaces.
- Gas (Water vapour): No fixed shape, flows in all directions, spreads to fill entire available space.

Given: The diagram shows the three states of water and the processes of conversion between them.

Filling the blanks:

States of water (Boxes A, B, C):
- A = Ice (Solid state)
- B = Water (Liquid state)
- C = Water Vapour (Gaseous state)

Processes of conversion (Boxes 1, 2, 3, 4):
- 1 = Melting (Ice → Water; on heating)
- 2 = Freezing (Water → Ice; on cooling)
- 3 = Evaporation (Water → Water Vapour; on heating)
- 4 = Condensation (Water Vapour → Water; on cooling)

Summary of conversions:
$$\text{Ice} \xrightarrow{\text{Melting (heating)}} \text{Water} \xrightarrow{\text{Evaporation (heating)}} \text{Water Vapour}$$
$$\text{Water Vapour} \xrightarrow{\text{Condensation (cooling)}} \text{Water} \xrightarrow{\text{Freezing (cooling)}} \text{Ice}$$

Conditions that affect the rate of evaporation:

1. Temperature: Higher temperature → faster evaporation. On a hot day, water evaporates much faster than on a cold day because more heat energy is available for the water molecules to escape into the air.

2. Exposed surface area: Larger surface area → faster evaporation. Water in a plate evaporates faster than water in a bottle cap because more water surface is exposed to air.

3. Air movement (wind): More wind → faster evaporation. A windy day causes faster evaporation because the water vapour formed is quickly carried away, allowing more water to evaporate.

4. Humidity: Lower humidity → faster evaporation. On a rainy day, the air already contains a lot of water vapour (high humidity), so water evaporates slowly. On a dry day, evaporation is faster.

Hot day vs. Cold day:
- On a hot day: Evaporation is fast. Clothes dry quickly, puddles disappear faster.
- On a cold day: Evaporation is slow. Clothes take longer to dry, puddles last longer.

Given: Equal amounts of water are taken in a bottle cap (small exposed area) and in a plate (large exposed area).

Expected Observation: The water in the plate evaporates faster (in less time) than the water in the bottle cap.

Conclusion: The exposed surface area of water affects the rate of evaporation.
- Greater the exposed surface area, faster is the rate of evaporation.
- The plate has a larger surface area exposed to air, so more water molecules can escape into the air at the same time, causing faster evaporation.

Table 8.4:

| Container | Exposed Surface Area | Time taken for complete evaporation |
|---|---|---|
| Bottle cap | Small | More time |
| Plate | Large | Less time |

Application: This is why wet clothes are spread out (not bunched together) to dry — spreading increases the surface area and speeds up evaporation.

Given: Equal amounts of water are taken in two identical bottle caps — one placed in sunlight and one in shade.

Expected Observation: The water in the cap kept in sunlight evaporates faster (disappears in less time) than the water in the cap kept in shade.

Conclusions:

1. Effect of temperature/sunlight: Water evaporates faster in sunlight because the sun provides more heat energy to the water molecules, enabling them to escape into the air more quickly. Higher temperature increases the rate of evaporation.

2. Effect of wind: Clothes dry faster on a windy day because moving air carries away the water vapour from the surface, allowing more water to evaporate. With increased air movement, evaporation is faster.

3. Effect of humidity: On a rainy day, the air already has high humidity (more water vapour), so water evaporates slowly. Clothes dry slowly on rainy days.

Summary: Evaporation is faster when:
- Temperature is higher (sunny/hot day)
- Air movement is more (windy day)
- Humidity is lower (dry day)
- Surface area is larger

Answer: Water stored in an earthen pot (*matka*) is cooler than water stored in a stainless steel pot because of the cooling effect of evaporation.

Explanation:
1. An earthen pot is made of clay and has tiny pores (small holes) on its surface.
2. Water slowly seeps through these tiny pores to the outer surface of the pot.
3. This water on the outer surface evaporates continuously.
4. During evaporation, the water absorbs heat from the water inside the pot (as heat is needed for evaporation).
5. This removal of heat from the water inside the pot makes the water cool.

Stainless steel pot: A stainless steel pot has no pores, so water cannot seep through. There is no evaporation from the outer surface, and hence no cooling effect.

Other examples of cooling effect of evaporation:
- Sprinkling water on the floor or roof during summer cools it down.
- We feel cooler when we sit under a fan — the fan speeds up evaporation of sweat from our body.
- Rubbing sanitiser on hands gives a cooling sensation.

Explanation:

1. Our body produces sweat when we feel hot. Sweat is mostly water.
2. When we sit under a fan, the moving air (wind created by the fan) flows over our skin.
3. This moving air increases the rate of evaporation of sweat from our skin.
4. Evaporation requires heat energy. This heat is taken from our body (skin).
5. As heat is removed from our body during evaporation of sweat, we feel cooler.

Key concept: Evaporation causes a cooling effect because it absorbs heat from the surroundings (in this case, from our body).

This is also why:
- Water in an earthen pot is cool (evaporation through pores cools the water).
- We feel cold when we apply sanitiser (it evaporates quickly, taking heat from our hands).

Answer: When we rub sanitiser on our hands, we feel a cooling sensation.

Reason:
1. Hand sanitiser contains alcohol, which evaporates very quickly.
2. When we rub sanitiser on our hands, it spreads over the skin and evaporates rapidly.
3. During evaporation, the sanitiser absorbs heat from our hands.
4. This removal of heat from the skin gives us a cooling effect.

This is the same principle as the cooling effect of evaporation — evaporation absorbs heat from the surface, making it feel cool.

Answer: On a rainy day, humidity is high and evaporation is slow. To dry clothes faster on a rainy day, we can:

1. Use a fan or place clothes in a well-ventilated area: Increased air movement speeds up evaporation by carrying away water vapour from the surface of the clothes.

2. Place clothes near a heater or in a warm room: Higher temperature increases the rate of evaporation.

3. Spread clothes out fully: Increasing the exposed surface area of the wet clothes allows more water to evaporate at the same time.

4. Use a clothes dryer: It provides heat and air movement simultaneously, making evaporation very fast.

5. Place clothes in a room with a dehumidifier: Reducing humidity in the room speeds up evaporation.

Key principle: Evaporation is faster at higher temperatures, with more air movement, and at lower humidity.

Observation:
- Without burnt newspaper: When the bottle is squeezed and released, little or no haziness is observed above the water.
- With burnt newspaper: When the bottle is squeezed and released, haziness (like clouds) is observed above the water in the bottle.

Explanation:
1. Squeezing the bottle increases pressure inside, and releasing it causes a sudden drop in pressure.
2. This drop in pressure causes the air inside to cool slightly.
3. The burnt newspaper provides very tiny, invisible dust particles (smoke particles).
4. Water vapour present in the bottle condenses around these dust particles, forming tiny water droplets.
5. These tiny water droplets appear as haze or clouds above the water in the bottle.

Role of dust particles: Dust particles act as condensation nuclei — tiny surfaces around which water vapour condenses to form water droplets. This is similar to how clouds form in the atmosphere, where water vapour condenses around dust particles present in the air to form tiny water droplets, which together appear as clouds.

Labelling of the Water Cycle Diagram (Fig. 8.9):

Storage locations:
- Ocean — Large water body where most of Earth's water is stored.
- Lake — Inland water body on the Earth's surface.
- River — Flowing water body that carries water from land to the ocean.
- Groundwater — Water stored underground, below the Earth's surface.
- Cloud — Water stored in the atmosphere as tiny water droplets.

Processes (shown with arrows):
- Evaporation — Arrow pointing upward from Ocean/Lake/River to the atmosphere. Water from the surface converts into water vapour and rises into the atmosphere.
- Condensation — Arrow showing water vapour in the atmosphere converting into tiny water droplets to form clouds.
- Rain — Arrow pointing downward from clouds to the Earth's surface (liquid water falling).
- Snow — Arrow pointing downward from clouds to mountains/cold regions (solid water falling).

Description of the Water Cycle:
$$\text{Ocean/Lake/River} \xrightarrow{\text{Evaporation}} \text{Water Vapour in atmosphere} \xrightarrow{\text{Condensation}} \text{Clouds} \xrightarrow{\text{Rain/Snow}} \text{Earth's surface} \rightarrow \text{Rivers/Groundwater} \rightarrow \text{Ocean}$$

This continuous circulation of water between the Earth's surface and the atmosphere is called the water cycle.

Correct Answer: (iv) The conversion of water vapour into its liquid state.

Justification: Condensation is defined as the process by which water vapour (gaseous state) converts into liquid water upon cooling. This happens when water vapour comes in contact with a cold surface (e.g., water droplets on the outer surface of a cold glass tumbler, dew drops on plants in the morning). Options (i) and (ii) describe evaporation, and option (iii) describes cloud formation, which is a result of condensation but not the definition of condensation itself.

Answer:

(i) Colouring: Evaporation is very important when colouring with (b) water colours.

Reason: Water colours are dissolved in water. When we apply water colours on paper, the water in the paint needs to evaporate for the colour to dry and set on the paper. Crayons and pencil colours are solid and do not involve water, so evaporation is not important. Acrylic colours dry partly by evaporation of water but also by a chemical process (polymerisation), but water colours rely primarily on evaporation.

(ii) Writing on paper: Evaporation is very important when writing with (b) ink pen.

Reason: Ink used in ink pens contains a liquid (water or solvent) in which the dye is dissolved. After writing, the liquid in the ink needs to evaporate for the ink to dry on the paper. Pencil and ball point pen use solid graphite and thick oil-based ink respectively, where evaporation plays little or no role.

Answer: The space around natural grass feels cooler than the space around plastic grass because of the cooling effect of evaporation (also called transpiration in plants).

Explanation:

1. Natural grass is a living plant. It absorbs water from the soil through its roots.
2. This water evaporates from the surface of the grass leaves (a process called transpiration).
3. During evaporation, heat is absorbed from the surroundings, which cools the air around the natural grass.
4. Additionally, natural grass also absorbs sunlight for photosynthesis rather than reflecting all of it as heat.

Plastic grass:
1. Plastic grass is not a living plant and does not contain water.
2. There is no evaporation or transpiration from plastic grass.
3. Plastic absorbs and retains heat from sunlight, making the surrounding area warmer.

Conclusion: Natural grass cools the surrounding area through evaporation of water, while plastic grass heats up the surrounding area by absorbing and retaining heat. This is why natural grass areas feel cooler.

Examples of liquids other than water that evaporate:

1. Alcohol (ethanol): Used in hand sanitisers; evaporates quickly giving a cooling sensation.
2. Petrol: Evaporates at room temperature; that is why we can smell petrol near fuel stations.
3. Acetone (nail polish remover): Evaporates very quickly.
4. Perfume/Cologne: The liquid perfume evaporates and spreads its fragrance in the air.
5. Kerosene: Evaporates slowly at room temperature.
6. Coconut oil: Evaporates slowly when heated.
7. Turpentine: Used in paints; evaporates and helps paint dry.

Common feature: All these liquids evaporate because their molecules gain enough energy to escape from the liquid surface and enter the gaseous state. Some evaporate faster (alcohol, acetone) and some slower (kerosene, coconut oil).

Answer: This is an interesting observation. Let us understand it clearly.

Why fans create a cooling sensation:
- When a fan blows air over our skin, it speeds up the evaporation of sweat.
- Evaporation requires heat, which is taken from our skin, making us feel cooler.
- The fan does not actually lower the temperature of the air — it just increases the rate of evaporation of sweat.

Why fans also dry wet clothes:
- Wet clothes have water on their surface. For this water to evaporate, it needs heat energy.
- The heat energy comes from the surroundings (the air, the room temperature).
- When a fan blows air over wet clothes, it continuously replaces the humid air (air with water vapour) near the clothes with drier air.
- This allows more water to evaporate from the clothes into the air.
- The fan does not make the clothes colder — it speeds up evaporation by increasing air movement.

Key understanding: A fan speeds up evaporation by increasing air movement. Whether it is sweat on our skin or water on wet clothes, faster evaporation occurs. In the case of our skin, we feel cooler because the heat is taken from our body. In the case of clothes, the heat comes from the surrounding air, so the clothes dry faster without us feeling that the fan is 'warming' the clothes.

Conclusion: Fans dry wet clothes by increasing the rate of evaporation through increased air movement, not by providing heat directly.

Answer: Leaving sludge in heaps next to the drain for 3–4 days before transporting it is a practical approach that uses the principle of evaporation.

How it reduces transportation cost:
1. Fresh sludge removed from drains contains a large amount of water.
2. When left in heaps for 3–4 days, the water in the sludge evaporates due to sunlight, heat, and air movement.
3. As water evaporates, the sludge becomes drier and lighter.
4. Dry sludge weighs much less than wet sludge.
5. Transporting lighter, drier sludge requires less fuel, fewer trips, and smaller vehicles, thereby reducing transportation costs significantly.

How it enhances safety of individuals handling it:
1. Fresh sludge from drains contains harmful bacteria, pathogens, and toxic gases (like methane and hydrogen sulphide).
2. When left to dry for 3–4 days, exposure to sunlight and air helps to:
- Kill many harmful microorganisms (UV rays from sunlight have a disinfecting effect).
- Allow toxic gases to escape into the atmosphere.
3. Dry sludge is also less slippery and easier to handle than wet sludge.
4. Workers handling dry sludge are at lower risk of infection and accidents compared to handling wet, fresh sludge.

Conclusion: Allowing sludge to dry through evaporation makes it lighter (reducing cost) and safer (reducing health risks) — a simple but effective application of the principle of evaporation.

Activities in the house that involve evaporation:

1. Drying wet clothes after washing — water evaporates from the clothes.
2. Mopping the floor — water on the floor evaporates and the floor dries.
3. Cooking — water evaporates from food while cooking (boiling, frying).
4. Sweating — sweat evaporates from our body, keeping us cool.
5. Applying sanitiser — alcohol in sanitiser evaporates quickly.
6. Storing water in an earthen pot — water seeps through and evaporates, keeping the water cool.
7. Drying hair after a bath — water evaporates from hair.
8. Drying dishes after washing — water evaporates from the surface of utensils.
9. Using perfume — the liquid perfume evaporates and spreads fragrance.
10. Sprinkling water on the roof in summer — water evaporates and cools the roof.

How understanding evaporation helps in daily activities:

1. Drying clothes faster: We know to spread clothes in sunlight and windy areas to speed up evaporation.
2. Keeping cool in summer: We use fans, wet cloth on forehead, and earthen pots — all based on cooling effect of evaporation.
3. Cooking efficiently: We understand why food dries out if left uncovered and why covered vessels retain moisture.
4. Water conservation: Understanding evaporation helps us cover water containers to prevent unnecessary water loss.
5. Health and hygiene: We understand why sanitisers work and why sweat helps regulate body temperature.

Answer: Water is present in the solid state in nature in the following forms:

1. Ice: Water freezes into ice when the temperature drops to $0°C$ or below. Ice is found in:
- Polar ice caps: Thick layers of ice cover the North Pole (Arctic) and South Pole (Antarctica).
- Glaciers: Large, slow-moving masses of ice found in mountain regions (e.g., Himalayan glaciers like Gangotri).
- Frozen lakes and rivers: In very cold regions, the surface of lakes and rivers freezes in winter.

2. Snow: When water vapour in clouds freezes, it forms snowflakes that fall as snow. Snow covers mountain peaks and cold regions.

3. Hail: Under special atmospheric conditions, water droplets in clouds freeze into small balls of ice called hailstones, which fall to the ground.

4. Frost: Water vapour directly freezes on cold surfaces (like leaves, grass, windows) forming a thin layer of ice crystals called frost.

Importance: Glaciers and polar ice caps store a large amount of fresh water. Glaciers are an important source of fresh water for rivers (e.g., the Ganga river originates from the Gangotri glacier).

Reflection on the statement: 'Water is our responsibility before it is our right.'

This statement is very meaningful and thought-provoking. Let us understand it:

Water as a Right:
- Every living being — humans, animals, and plants — needs water to survive.
- Access to clean, safe water is considered a basic human right.
- We have the right to use water for drinking, cooking, bathing, agriculture, and other needs.

Water as a Responsibility:
- While we have the right to use water, we also have the responsibility to use it wisely and not waste it.
- Only a small fraction of Earth's water is fresh water suitable for use. Most water is in the oceans (salty) and cannot be used directly.
- The demand for water is increasing due to growing population, while the supply remains limited.
- Water bodies are being polluted by industrial waste, sewage, and garbage, making water unsafe.

My thoughts:
1. We must use water carefully and avoid wasteful habits (like leaving taps running, overwatering plants).
2. We should keep water bodies (rivers, lakes, ponds) clean and free from pollution.
3. We should practise rainwater harvesting to conserve water.
4. We should repair leaking taps and pipes promptly.
5. We should educate others about the importance of water conservation.

Conclusion: Water is precious and limited. Before claiming our right to use water, we must fulfil our responsibility to conserve it, use it wisely, and protect it from pollution — for ourselves and for future generations.

Answer: We can cool down the hot seat of a two-wheeler by sprinkling or pouring water on it.

Explanation:
1. When water is sprinkled on the hot seat, it starts to evaporate because the seat is very hot.
2. During evaporation, water absorbs heat from the seat surface.
3. This removal of heat from the seat causes it to cool down.
4. After a short while, the seat becomes cool enough to sit on.

Principle used: This works on the cooling effect of evaporation — evaporation absorbs heat from the surface, thereby cooling it.

Other similar examples:
- Sprinkling water on the floor or roof during summer to cool it.
- Wet cloth placed on the forehead to reduce fever.
- Water stored in an earthen pot stays cool due to evaporation through its pores.

Additional tip: We can also cover the seat with a cloth or park the two-wheeler in the shade to prevent it from getting too hot in the first place.