energy transfers by heating (required practicals) Flashcards
what is specific heat capacity?
how much energy is required to heat 1kg of a substance by 1°C.
what is the formula for specific heat capacity?
thermal energy required jules = mass kg x specific heat capacity jules/kg x temperature change °C
how do you find the specific heat capacity of a solid material? (required practical)
to measure the specific heat capacity:
1. you need a block of the material with 2 holes (1 for a immersion heater and 1 for a thermometer)
2. measure the mass of the material then wrap it in an insulating material (to reduce energy lost to the surroundings)
3. insert the thermometer and heater
4. measure the starting temperature of the material
5. connect a power pack set to 10V to the heater and an ammeter
6. switch on the power pack and start a timer
when the heater is on the circuit does work transferring energy electrically to the heaters thermal store
7. take the materials temperature for 10 minutes once a minute then turn off the power pack
8. calculate power from volts x current and then calculate energy transferred with power x time
9. rearrange energy = mass x specific heat capacity x temperature change to find the heat capacity
what does conduction usually occur in?
solids.
what does convection usually occur in?
liquid and gases.
what is conduction?
the process where vibrating particles collide with other particles transferring energy.
what energy store is energy transferred by heating stored in?
thermal energy store.
how is energy shared in the thermal energy store?
energy is shared across the kinetic energy stores of particles in an object.
how does conduction work?
particles in an object heat up and vibrate colliding with other particles which transfers energy between kinetic stores.
what is thermal conductivity?
a measure of how quickly energy is transferred through a material by conduction.
what is convection?
a process where energised particles move from hot to cold regions.
how does convection work?
particles in liquids and gases are free to move and so when you heat them the distance between each particle increases and the density decreases causing the less dense regions to rise above the cooler denser regions.
what are convection currents?
because liquids and gases can flow warm less dense regions rise above falling cooler denser regions creating a constant circulation of hot and cold areas.
what is an example of an appliance that creates convection currents?
a radiator.
how do you reduce energy transferring from heating?
insulation.
