Thermal Energy (Chapter P2) Flashcards
What is a system?
A system is an object or group of objects
What are all the different stores
Thermal store Elastic store Kinetic store Gravitational store Nuclear store Chemical store Electrostatic store Magnetic store
What is the thermal store
Energy due to an object’s temperature. Thermal stores increase when the object gets hotter and decrease when it gets colder
What is the Elastic store
Energy due to an object having a greater/shorter length than its natural length. Elastic stores increase if the object is stretched or squashed from its natural shape and decrease if it returns to its natural shape.
What is the Kinetic store
Energy due to an object’s mass and speed. Kinetic stores increase if an object’s speed increases and decrease if an object is slowed down.
What is the Gravitational store
Energy due to an object’s height above the Earth’s surface. Gravitational stores increase if an object is lifted up and decrease if it falls down.
What is the Chemical store
Energy due to atoms combining in a chemical reaction.
What is the Electrostatic store
This is energy stored when similar charged objects are pushed together and when opposite charged objects are pulled apart.
What is the Nuclear store
This is energy associated with the nucleus of an atom. This changes if changes happen in the nucleus e.g. in a fusion reaction
What is the Magnectic store
This is the energy stored when like poles of a magnet are pushed closer together and unlike poles are pulled further apart.
What are the energy transfers
Forces doing work A flow of an electrical current Heating Light Radiation Sound waves
What is internal energy?
Internal energy is the total kinetic and potential energy of all the particles (atoms and molecules) that make up a system. The molecules’ kinetic store is related to how fast they are moving, and the molecules’ potential store is related to how far apart they are (their bonds).
What is the equation for change in energy
= mass x specific heating capacity x change in temp
What is specific heat capacity
The specific heat capacity of a substance is the energy (in J) needed to increase the temperature of 1 kg of a substance by 1 degree (or Kelvin can be used too)
What is accurate data?
Accurate data is data which is close to the true value
What is precise data?
Precise data is data in which repeated measurements show very little spread about the mean value.
What is reproducible data?
If another person can get the same result with the same, or different method/equipment, then the data is reproducible
What is repeatable data?
If the same person can get the same result with the same equipment and method then the data is repeatable.
What is random uncertainty?
Random uncertainty causes measurements to be spread around a mean value. The effect of random uncertainty can be reduced by repeating and averaging data.
What is systematic uncertainty?
Systematic uncertainty occurs when measurement is always too high or too low for each repeat. Usually because of an error in the equipment e.g a badly calibrated thermometer.
What is a zero error?
This is a type of systematic uncertainty which occurs when a measuring instrument reads a value when it should say zero. E.g. a mass balance which doesn’t say zero when there is nothing on it.
What factors affect the rate of cooling of a building?
The thickness of the building’s walls and the thermal conductivity of its insulation affect the rate of cooling.
What is specific latent heat
The specific latent heat of a substance is the amount of energy (in J) required to change the state of 1 kg of the substance with no change in temperature.
The specific latent heat of fusion is the amount of energy required to change the state of 1 kg of a substance from solid to liquid with no change of temperature.
The specific latent heat of vaporisation is the amount of energy required to change the state of 1 kg of a substance from liquid to gas with no change of temperature.
What is the equation for energy and latent heat
energy = mass x latent heat
What is thermal conductivity
How good a material is at transferring energy by conduction
What does a material with a high thermal conductivity mean
It is a good conductor and can transfer energy very quickly by conduction
What does the rate of energy transfer depend on in an insulating material
The temperature difference across the material
The thickness of the material
The thermal conductivity of the material
Where does most infrared radiation come from
The Sun
What is the wavelength of infrared waves
longer than visible light
What happens to the infrared levels when an object gets hotter
More infrared radiation is emitted
What is black body radiation
It is radiation emitted by a body that absorbs all the radiation going towards it
what happens if an object absorbs more infrared radiation than it emits
The temperature of it increases
What factors does the earth’s temperature depend on
Absorption of infrared radiation from the Sun
The emission of radiation from the earth’s surface and atmosphere
What is the equation for specific heat capacity
c = Energy transferred / mass x temp change
What is the unit for specific heat capacity
J/kg degrees
How does mass effect the rate at which an objects temperature increases
the greater the mass of an object, the slower its temperature increases
What can reduce the energy transfer in a house
Loft insulation Cavity wall insulation Double-glazed windows aluminium foil behind radiators external walls with lower thermal conductivity
what is cavity wall insulation
It is insulation material used to fill the gaps between 2 brick layers of an external wall
