Question

Your body feels cooler when you step out of a warm shower because a) water evaporates on your skin. b) water condenses on your skin. c) water evaporates from the surrounding air. d) water condenses in the surrounding air.

Short answer

a) water evaporates on your skin.

Step-by-step solution

Understanding the Scenario

When you step out of a warm shower, your skin is wet because of the water droplets left on your skin.

Identifying the Process of Evaporation

Evaporation is the process where water molecules on your skin gain enough energy to change from a liquid to a vapor. This process absorbs heat from your skin, which makes you feel cooler.

Analyzing the Options

Option a) suggests that water evaporates on your skin, which aligns with the cooling effect we feel. Option b) refers to condensation on your skin, which doesn't cool as it involves releasing heat. Options c) and d) refer to the surrounding air, not directly linked to the immediate cooling effect you feel. Thus, they are less relevant.

Key concepts

Thermal Energy Transfer

Thermal energy transfer is the movement of heat energy from one object to another. This can happen in various ways, such as conduction, convection, and radiation. In the case of feeling cooler when stepping out of a warm shower, the key process is the transfer of heat from your skin to the water molecules.

This is an example of energy transfer known as evaporation. As the water on your skin evaporates, the faster-moving molecules with higher kinetic energy escape into the air.

• Since these molecules take energy or heat with them, the surface left behind—your skin—feels cooler.
• This process highlights how heat energy moves from a warmer object (your body) to a cooler one (the air) via the medium of water.

Understanding thermal energy transfer helps us grasp how heat is gained or lost in different physical environments.

Phase Change

A phase change refers to the transformation from one state of matter—solid, liquid, or gas—to another.

In the context of stepping out of a shower, the phase change from liquid to gas is crucial. This change takes place during evaporation when liquid water on your skin becomes vapor.

• Evaporation occurs at the surface and doesn't require boiling. It's one of the everyday phase changes that play a significant role in our climate and body temperature regulation.
• Phase changes such as this involve the absorption or release of energy without changing temperature initially. This is important in maintaining balance in the body's internal temperature as well.

The understanding of phase changes is key to comprehending natural phenomena and everyday experiences, like feeling cooler after a shower.

Heat Absorption

Heat absorption is central to the cooling effect felt when water evaporates from your skin. During evaporation, water absorbs thermal energy from its surroundings, particularly your skin.

This energy boost enables water molecules to transition from a liquid state to a gaseous state.

• When water absorbs heat, it doesn't immediately raise its temperature. Instead, this energy is used to break the intermolecular bonds, aiding in the phase change.
• This absorbed heat, known as latent heat, helps in regulating body temperature by efficiently removing excess body heat from your skin.

Heat absorption during evaporation is a basic principle behind evaporative cooling, which not only cools our skin but also helps control climate temperatures globally.