In this topic we are learning to: z Investigate the ways in which heat moves through solids, liquids and gases.
z Distinguish between conductors and insulators of heat.
z Compare the colour of an object with its ability to absorb and emit radiated heat.
Heat is a form of energy. This energy transfers from a hot place to a cold place. It can do this in three ways:
1. Conduction 2. Convection 3. Radiation.
Conduction Particles vibrating fast Candle Fig. 19.5.1
A heated spoon conducts heat through fast- vibrating particles
Fast and slow melting
Plan, design, carry out and write up an investigation to determine the rate at which a cube of ice will melt when placed on top of the following substances:
a. Glass b. Wood c. Perspex Consider the following:
1. How will you make this a fair test? What will you measure and how will you measure it?
2. Predict the rate at which the ice cube will melt when placed on top of each of the substances. Then explain why your observations did or did not match your predictions.
States of matter as conductors
Create a poster explaining why solids are generally the best conductors of heat, followed by liquids then gases. Use your knowledge of the particle theory to support your explanation.
340 340 F
Baked Alaska is a dessert made of ice cream surrounded by meringue. The air in the meringue insulates the ice cream from the heat, stopping it from melting.
Fig. 19.5.2 Baked Alaska
d. Aluminium e. Styrofoam board f. Copper
Solids transfer heat through conduction. z When heat energy is transferred to a solid, it causes the particles of the solid to vibrate quickly.
z These vibrations pass through the rest of the solid, conducting the heat.
Conductors, such as metals, feel cold to the touch as they quickly draw heat away from your body.
