P2 Energy Transfer by Heating Flashcards
The equation for change of state
E=ml
E is the thermal to or lost by the body (J)
m is the mass of the body (kg)
l is the latent heat (Jkg-1)
What is equal to 0 Kelvin
-273°C
What is the lowest ever recorded temperature
0 Kelvin (-273°C)
Can Kelvin ever be negative
No
Latent heat
The energy transferred to or from a substance during its change if state
Internal Energy
The energy of the particles of a substance due to their individual motion (movement) and positions
Thermal
A form of energy, measured in joules (j)
Specific heat capacity of fusion
Energy needed to melt 1kg of a substance with no change of temperature
What are the best conductors of energy
Metals are the best conductors of energy
What are the best insluators
Non-metals, such as wool and fibre class are the best insulators
What links a materials thermal conductivity and the rate of energy transfer
The higher the thermal conductivity of the material the quicker the rate of energy transfer through it
What is the effect of a the thickness of an insulatoring
The thicker a layer of insulating material is, the lower the rate of energy transfer through it.
Which sort of objects emit and absorbs infrared radiation?
All objects absorb and emit infrared radiation
How does the temperature of an object effect the amount of infrared radiation emitted
The hotter the object is, the more infrared radiation it emits in a given time
What’s black body radiation
Radiation emitted by a body that absorbs all the radiation incident on it (no other object emits or absorbs radiation as effectively as a perfect black body).
How does the temperature of an object increase
If it absorbs more radiation than it emits
What does the temperature of the Earth depend on
Lots of factors, including the absorbtion of infrared radiation from the sun, and the emission of radiation from the Earth’s surface and atmosphere.
Specific heat capacity
Specific heat capacity of a substance is the amount of energy needed to change the temperature of 1kg of the substance by 1°C
Specific heat capacity equation
Energy transferred= mass x specific heat capacity x temperature change
^E= mc^theta
How does the mass effect the rate at which temperature increases
The greater the mass of an object, the more slowly its tempertaure increases when heated
What do you use to measure the change in energy
Joulemeter
What do you use to measure the change in temperature
Thermometer
What’s the rearranged equation to find specific heat capacity
C= ^E / m^theta
What can be used to heat a house
Electric/gas heaters
Gas and oil fired central heating
Solid fuel stoves
How can the rate of energy transfer from houses be reduced?
Lost insulation
Double glazed windows
Aluminium foil behind rediators
External walls with thicker bricks and lower thermal conductivity
What’s cavity wall insulation
Insulation material used to fill up the cavity between to brick layers of an external house wall
