Heat Transfer in Nature

Overview

Heat moves from hotter to cooler objects. This chapter explains the three ways heat travels: conduction, convection and radiation, and how they appear in nature.

Key concepts

• Heat always flows from a hot body to a cold body.
• Conduction transfers heat through solids by contact.
• Convection transfers heat through liquids and gases by movement.
• Radiation transfers heat without any medium (e.g. from the Sun).
• Temperature is measured using a thermometer.

Important terms / formulae

• Conduction: heat flow through a material by contact.
• Convection: heat flow by movement of fluid.
• Radiation: heat flow as rays, needing no medium.
• Temperature: measure of how hot or cold a body is.

Solved example or key process

When water is heated in a pan, the bottom layer warms first, becomes lighter and rises, while cooler water sinks. This circulation is a convection current. The pan handle warming up shows conduction, and feeling warmth from the flame shows radiation.

Important questions

1. Name the three ways heat is transferred.
2. How does heat from the Sun reach the Earth?
3. Give one everyday example of convection.
4. Why are cooking pans made of metal but handles of plastic?

Quick revision

Heat flows from hot to cold by conduction (solids), convection (fluids) and radiation (no medium). The Sun warms us through radiation, and boiling water shows convection.