Concept 8: Heat Transfer
I can explain how heat can move using convection, conduction and radiation.
Hei Mahi in your book/laptop:
What are 3 things you do in winter to keep warm?
What are 3 things you do in summer to keep cool?
Hei Mahi on the piece of paper:
Write a creative short story on how heat transfer is affecting the person in this cartoon.
What should he do to prevent himself from getting heat stroke?
What is Heat?
Heat is a form of energy that can be transferred from one object to another. Temperature is a measure of the average kinetic energy of particles in a substance.
The particles in a substance are vibrating and moving. The more they are moving, the higher the temperature.
Heat always flows from hot to cold. Energy transfers always occur from higher energy to lower energy states. Energy flows 'downhill'.
Mechanisms of Heat Transfer
There are 3 mechanisms of heat transfer: conduction, convection, and radiation.
Conduction is the transfer of heat energy by direct contact. The particles within a hot object vibrates and causes neighbouring particles to vibrate.
Materials that allow heat to travel them are called conductors. Metals are good conductors of heat. Non-metals are poor conductors and are called insulators.
The more the particles vibrate, the higher the temperature.
Convection is the transfer of heat energy by movement of liquid and gas particles from one place to another.
When heated, a substance expands and becomes less dense. This creates a convection current as the hotter substance rises.
This explains why the breeze comes from the ocean during the day and from the land at night.
Radiation is the transfer of heat energy by electromagnetic waves. It can occur through empty space.
Like light, heat can be absorbed or reflected by objects. Why or shiny surfaces reflect more heat energy than black or dull surfaces. Any warm object radiates heat.
We rely on the sun's radiation to provide energy to our planet.