Heat Transfer Flashcards
(22 cards)
Define conduction
The way heat travels through solids
What is a conductor?
A material which lets energy flow through it easily
What is a convection current?
A current created by heat causing changes in the density of a fluid
What is a heat insulator?
Material that does not let heat energy flow easily through it
What is Infrared Radiation?
A wave that can travel through transparent things and a vacuum (empty space)
What is an insulator?
A material that does not let energy flow through it easily
What are Joules?
The units for measuring energy
What is radiation?
The transfer of heat energy by electromagnet waves
Which colour reflects heat the best?
Shiny surfaces and white (silver)
Which colour absorbs heat the best?
black (particularly matte black)
What colour releases heat the best?
black
How do windows insulate?
Double glazing traps air between the two glass panes, and since air does not conduct heat well it keeps the heat in the house
How are walls in modern houses insulated?
Foam, which contains air bubbles which cuts conduction and prevents convection currents
How can radiators be insulated to prevent escaping heat
Shiny, silver sheets which reflect the heat are placed between the radiator and the wall since silver reflects heat
Why will a hot cup of tea gradually cool over time?
Because the tea gives out heat energy to its surroundings
Why will a cool drink straight out of the fridge warm up over time?
Because the cold drink will take in energy from its surroundings
Define temperature. How is it measured?
A measure of how hot or cold something is. It’s determined by the average kinetic energy in the particles of the object
How well do solids conduct heat?
Solids (especially metals such as copper and aluminium) conduct heat well
Why do metals conduct heat well?
The outer electrons in metal atoms drift and are free to move. When the metal is heated, this ‘Sea of Electrons’ gain kinetic energy and transfer it quickly throughout the metal.
How well do liquids conduct heat?
Not very well, they are poor conductors
How well do gasses conduct heat?
Not very well, they are poor conductors
Describe how a convection current is formed (3 steps)
- The Bunsen burner heats the liquid/gas
- The hot water/gas expands, becomes less dense and begins to rise
- Cooler, denser liquid/gas sinks to replace the rising substance, and so a convection current is formed
