Topic 2 - Energy transferred by heating Flashcards
Another name for how fast an object conducts heat is its?
Thermal conductivity.
The energy transferred per second through an object depends on three things, name and describe these things.
1) The temperature difference across the material, the higher the difference the higher the rate of transfer.
2) The thickness of the material, the thicker a material, the less energy will be transferred per second.
3) The thermal conductivity of the material, the higher the conductivity, the faster the rate of transfer.
What type of radiation do we absorb from the sun?
Infrared radiation.
What material is best for the absorption and emission of infrared radiation?
Matte black surfaces.
What is a perfect black body?
A theoretical object that absorbs 100% of radiation that hits it.
When matte black and silver materials are used as a covering for a boiling tube, which one cools faster?
Matte black cools faster as energy is easily dissipated to the surroundings.
How does the amount of layers of insulation affect the rate of thermal energy loss?
The higher the amount of layers that cover a beaker of boiling water, the slower the rate of energy loss.
On average, which retained the highest temperature after 10 seconds?
1) A beaker with 0 layers of insulation.
2) A beaker with 1 layer of insulation.
3) A beaker with 2 layers of insulation.
4) A beaker with 3 layers of insulation.
4) A beaker with 3 layers of insulation as the material is thickest and energy loss by dissipation is slowest.
What two factors of infrared radiation affect the temperature of the earth?
1) The energy reflected back out into space from earth’s atmosphere or surface.
2) The energy emitted from the earth’s atmosphere and surface into space.
Why would the earth’s temperature fall to below -180 degrees Celsius if it didn’t have an atmosphere?
The earth wouldn’t be trapping any infrared radiation and only reflecting it back out.
What three factors does an object’s temperature rise depend on?
1) the amount of energy supplied to the object.
2) The mass of the substance.
3 It’s specific heat capacity.
If experiments showed 4000J were needed to raise 1 kg of water by 1 degree celcius, what would be the specific heat capacity of water?
Around 4000J
What is the word equation for specific heat capacity?
Energy transferred (J) = mass (kg) x specific heat capacity (J/kg degrees celcius) x temperature change (degrees Celsius)
How would you rearrange the specific heat capacity equation to make specific heat capacity the subject?
Specific heat capacity = Energy Transferred (J) / mass (kg) x temperature change (degrees Celsius).
How does loft insulation reduce energy loss in a house?
Loft insulation reduces thermal energy lost through the roof by insulating the roof with fibreglass, reducing heat loss by conduction (through the material) and convection (across air gaps in the material).
