Aim How does heat transfer Do Now Explain

Aim: How does heat transfer? Do Now: Explain what happens when a pot of water is put on a stove.

Conduction (touch)

How do nonmetals conduct heat? 3 of 10 © Boardworks Ltd 2009

Convection (density)

Warmer regions of a fluid are less dense than cooler regions of the same fluid. The warmer regions will rise because they are less dense. The cooler regions will sink since they are more dense. This is how heat transfer takes place in fluids. It is called convection. The steady flow between the warm and cool sections of a fluid, such as air or water, is What is convection? called a convection current.

How does convection in a liquid occur?

Why is the freezer compartment at the top of a fridge? The freezer compartment is at the top of a fridge because cool air sinks. The freezer cools the air at the top and this cold air cools the food on the way down. It is warmer at the bottom of the fridge. This warmer air rises and so a convection current is set up inside the fridge, which helps to keep the fridge cool. Why is convection important in fridges?

Conduction and convection – summary

Radiation (waves)

Heat source-Any device or natural body that supplies heat. Heat sink- A device or substance that absorbs heat.

Closed system: A system in which no energy can get in or get out. Energy can be transferred from one part of the system to another. Since nothing can escape, the energy lost by the source (the hot water) must be exactly equal to the energy gained by the sink (the cold water). Open system: A leaky system. Energy leaks out of or into the system. In this case not all of the energy lost by the hot water is gained by the cold water. Much of the energy escapes into the environment (radiation from the aluminum bar).