KS 4 Heat transfer Boardworks Ltd 2003 Heat

KS 4 Heat transfer © Boardworks Ltd 2003

Heat transfer In which direction does heat move? “Heat energy always armer moves from w______ ooler areas. ” to c_____ © Boardworks Ltd 2003

Solids, liquids and gases What do the particles look like in a solid, a liquid and a gas? Liquid Gas Solid © Boardworks Ltd 2003

Conduction When you heat a metal strip at one end, the heat travels to the other end. As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction © Boardworks Ltd 2003

Metals are different The outer e_______ lectrons for metal atoms drift, and are free to move. When the metal is heated, this ‘Sea of inetic electrons’ gain k_____ energy and transfer it throughout the metal. Insulators, such as w___ ood and p____, lastic do not have this ‘Sea of electrons’ which is why they do not conduct heat as well as metals. © Boardworks Ltd 2003

Why does metal feel colder than wood, if they are both at the same temperature? Metal is a conductor, wood is an insulator. The metal conducts the heat away from your hands, the wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal. © Boardworks Ltd 2003

Insulating layers of air Other uses of a trapped insulating layer of air are. Clothing Ceiling tiles Cavity walls Fibreglass Fur coats Wallpaper © Boardworks Ltd 2003

Insulators insulating layer of air Double glazing keeps your house warmer because the ir between the layer of a__ panes of glass is a poor onductor so it acts like an c_______, nsulator it reduces heat loss i_______, by conduction from your house. © Boardworks Ltd 2003

Heating fluids What happens to the particles in a liquid or a gas when you heat them? The particles spread out and become less dense. This effects What A liquid isfluid aorfluid? gas. movement. © Boardworks Ltd 2003

Fluid movement Cooler, more d____, ense fluids sink through w_____, armer less dense fluids. In effect warmer liquids and gases r___ ise up. Cooler liquids and gases s___. ink © Boardworks Ltd 2003

Water movement Cools at the surface Cooler water sinks Convection current Hot water rises © Boardworks Ltd 2003

Why is it windy at the seaside? © Boardworks Ltd 2003

Cold air sinks Where is the freezer compartment put in a fridge? It is put at the top, because cool air sinks, so it cools the food on the way down. Freezer compartment It is warmer at the bottom, so this warmer air rises and a convection current is set up. © Boardworks Ltd 2003

The third method of heat transfer How does heat energy get from the Sun to the Earth? ? There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. RADIATION © Boardworks Ltd 2003

Radiation travels in straight lines True/False Radiation can travel through a vacuum True/False Radiation requires particles to travel True/False Radiation travels at the speed of light True/False © Boardworks Ltd 2003

Emission experiment Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Dull metal Shiny black Dull black shiny metal container would be the warmest after ten The _____ radiation back minutes because its shiny surface reflects heat _______ dull black container into the container so less is lost. The ____ emitting heat would be the coolest because it is the best at _______ radiation. © Boardworks Ltd 2003

Absorption experiment Four containers were placed equidistant from a radiative heater, which container would have the warmest water after ten minutes? Dull metal Shiny black Dull black dull black container would be the warmest after ten The _____ radiation the best. minutes because its surface absorbs heat _______ shiny metal container would be the coolest because it is The _____ the poorest at _____ absorbing heat radiation. © Boardworks Ltd 2003