Thermal Energy Definitions Flashcards
(35 cards)
System
A system is an object or group of objects.
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.
Thermal store
Energy due to an object’s temperature. Thermal stores increase when the object gets hotter and decrease when it gets colder.
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.
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.
Chemical store
Energy due to atoms combining in a chemical reaction.
Electrostatic store
Energy stored when similar charged objects are pushed together and when opposite charged objects are pulled apart.
Nuclear store
Energy associated with the nucleus of an atom. This changes if changes happen in the nucleus e.g. in a fusion reaction.
Magnetic store
Energy stored when like poles of a magnet are pushed closer together and unlike poles are pulled further apart.
Energy transfers
Energy transfers happen because of forces doing work, a flow of an electrical current, heating, light radiation, and sound waves.
Internal energy
The total kinetic and potential energy of all the particles (atoms and molecules) that make up a system.
Effect of heating on internal energy
When a substance is heated, the energy transferred to it increases the internal energy of the system, raising the temperature or causing a change of state.
Temperature and kinetic energy of gas
As the temperature of a gas increases, the average kinetic energy of the molecules also increases, meaning the particles move around more quickly.
Change in energy formula
ΔE = m × C × Δθ, where ΔE is energy (Joules, J), m is mass (kilograms, kg), C is specific heat capacity (J/kg℃), and Δθ is change in temperature (℃ or Kelvin, K).
Specific heat capacity
The energy (in J) needed to increase the temperature of 1 kg of a substance by 1 °C (or Kelvin can be used too).
How to measure specific heat capacity
The mass of the metal block is measured using a balance, and energy is transferred to the block by an immersion heater connected to a power supply, measured using a joulemeter.
Insulation
Reduces the amount of energy that is transferred to the surroundings, which reduces uncertainty in the value for the specific heat capacity.
Specific heat capacity formula
Specific heat capacity (S) = energy transferred / (mass x change in temperature).
Accurate data
Data which is close to the true value.
Precise data
Data in which repeated measurements show very little spread about the mean value.
Reproducible data
Data is reproducible if another person can get the same result with the same, or different method/equipment.
Repeatable data
Data is repeatable if the same person can get the same result with the same equipment and method.
Random uncertainty
Causes measurements to be spread around a mean value; can be reduced by repeating and averaging data.
Systematic uncertainty
Occurs when measurement is always too high or too low for each repeat, usually due to an error in the equipment.
