Heat Flashcards
What is heat
The ability to do work or move something meaning it is a form of energy
What energy sources can heat be converted into
Light Heat Kinetic Electricity Chemical
What is heat measure in
Joules (J)
Name some disadvantages of expansion and contraction
Long lengths of railway track need taper joints to allow for expansion in hot weather
Large slabs of concrete can buckle in heat if not given room to expand
A 700m bridge can be 25cm longer in summer than winter
Name some advantages of expansion and contraction
Thermometers work on a basis that liquid expands when heated and contracts when cooled
Bimetallic strips are used to trigger alarms or switch of heating. It is made of 2 metals put together and when one gets hot it bends and triggers the alarm
Expansion is used to a great effect in car engines or in rockets
When does water break its contract
When it reaches 4°C expands again
Name an advantage and a disadvantages of water expanding at low temperatures
- in cold weather water pipes burst due to water freezing and expanding
- fish can survive in lakes at very cold weather, water is at its most dense when it reaches 4°C, being warm so the denser the water the warmer the water
How does heat transfer
- Moves from a warm object to a less warm object
- Convection
- Conduction
- Radiation
How does conduction work
- Solids pass heat from particle to particle called conduction
- Metals are good conductors of heat
- Conduction is the method by which heat travels from particle to particle through a solid e.g. A long metal spoon
What is an insulator
A substance which does does not allow heat to pass through easily e.g. A wooden spoon
How does convection work
The transfer of heat through a liquid or gas when the particles of the liquid or gas move and carry the heat with them
How does radiation work
Is the rapid transfer of heat from a hot object without needing a medium
What is the effect of pressure on the boiling point of water
Pure water does not always boil at 100°
On mt Everest water boils at 70°
It boils at a lower temperature because pressure is low
Name some changes of state
3 states of H2o are water, ice, steam
What is latent heat
Heating ice
- heat crushed ice in a beaker, the temperature should rise with time till it reaches 0°, even though heat is being supplied the temperature stays at 0° until all the ice is melted the the temperature will rise again
Heating water
- water temperature rises till 100° then is does the same thing, when all the water turns to steam then the temperature rises again
Latent heat is the heat taken or given out when a substance changes state without changing temperature
