Question

Identify each of the following changes of state as evaporation, boiling, or condensation: a. The water vapor in the clouds changes to rain. b. Wet clothes dry on a clothesline. c. Lava flows into the ocean and steam forms. d. After a hot shower, your bathroom mirror is covered with water.

Short answer

a. Condensation b. Evaporation c. Boiling d. Condensation

Step-by-step solution

Understand the process of condensation

Condensation is the process where gas changes into a liquid. This occurs when vapor in the air cools and changes back into liquid form.

Analyze the first scenario

For the first scenario, 'The water vapor in the clouds changes to rain,' the water vapor (gas) turns into liquid rain. This is an example of condensation.

Understand the process of evaporation and boiling

Evaporation is the process where liquid turns into gas at temperatures below the boiling point. Boiling occurs when a liquid turns into gas at its boiling point, marked by the formation of bubbles.

Analyze the second scenario

For the second scenario, 'Wet clothes dry on a clothesline,' the water in the clothes (liquid) turns into water vapor (gas) at temperatures below boiling point. This is an example of evaporation.

Analyze the third scenario

For the third scenario, 'Lava flows into the ocean and steam forms,' the water from the ocean (liquid) is rapidly heated by the lava and turns into steam (gas). This is an example of boiling.

Analyze the fourth scenario

For the fourth scenario, 'After a hot shower, your bathroom mirror is covered with water,' the steam in the bathroom (gas) cools and turns into water droplets on the mirror. This is an example of condensation.

Key concepts

Condensation

Condensation occurs when a gas turns into a liquid. This process typically happens when the gas cools down. For example, think about clouds. They are formed when water vapor in the air cools down and condenses into tiny water droplets.
Condensation takes place in everyday life too.

• When you see dew on grass in the morning, that's condensation.
• Water droplets on the outside of a cold beverage is another example of condensation.

Now, apply this to our exercise:

• In scenario (a), water vapor in the clouds cools down and changes into rain. This is condensation.
• In scenario (d), steam from your shower cools on the mirror, forming water droplets. This is also condensation.

Evaporation

Evaporation is the process where a liquid turns into a gas at temperatures below its boiling point. This is different from boiling as it happens only at the surface of the liquid and does not require high temperatures.
For example, when you spill water on the floor, it eventually dries up. What's happening is evaporation.

• It’s why puddles disappear after the rain.
• Evaporation is also how sweat cools your body.

Now, let’s see it in our exercise:

• In scenario (b), wet clothes dry on a clothesline as the water evaporates into the air. This is evaporation.

Boiling

Boiling happens when a liquid changes into a gas at a specific temperature called the boiling point. You will notice bubbles forming throughout the liquid. This is different from evaporation which happens only at the surface.
For instance, when you heat water on a stove, it starts to boil at 100°C (212°F).

• Boiling happens rapidly and throughout the liquid.
• It’s why you see bubbles when water boils.

Let's look at our exercise:

• In scenario (c), lava flows into the ocean, heating the water rapidly to its boiling point and turning it into steam. This is boiling.