# Is air a good conductor of heat?

## Understand physics 3, textbook

12 1  Workbook page 6–7 Heat conduction - energy transfer through particle collisions 1. What happens with heat conduction? The hot nail and the cool fingers (Fig.12.1) E1 Take an iron nail between your thumb and forefinger. Hold the tip in the burner flame until you feel the nail heating up. Then place the nail on a heat-resistant surface. If the tip of an iron nail is heated, the iron particles begin to vibrate faster at this point. When they collide, they also stimulate the neighboring particles to vibrate more strongly. This is how they pass on part of their energy. 2. Which materials are good and which materials are bad conductors of heat? Who can feel the warmth faster? (Fig.12.2) E1 Hold a piece of copper wire, an iron knitting needle and a glass rod at the same time in the burner flame. Who will feel the warming first? Metals conduct heat energy very well. Their particles are close together. Silver and copper are the best heat conductors of all metals. Aluminum is also a good conductor of heat. It is used, for example, to manufacture heat sinks for electronic components. It dissipates the heat that would otherwise impair the function of these components. Water is a poor conductor of heat. The mobile water particles cannot transmit the particle collisions well. The particularly poor thermal conductivity of air can be explained by the relatively large distances between the air particles. Air-filled cavities, for example in hollow bricks, in windows with multiple glazing or wool sweaters, use the very poor thermal conductivity of the air. V1 12.1 The hot nail and the cool fingers In thermal conduction, the thermal energy is transferred through the collision of vibrating particles. M V2 12.2 Who can feel the warmth faster? 12.3 Energy transfer through strong particle movement All metals, especially silver, copper and aluminum, are good heat conductors. Bad heat conductors are, for example, glass, plastics, wood, water and air. M 12.4 Hollow bricks with air-filled cavities for better insulation 12.5 Cookware with metal bases 12.6 Insulation of exposed heating pipes with foam For test purposes only - property of the publisher öbv