Energy Flashcards
(28 cards)
What is a system?
A system is an object or a group of objects that interact.
Thermal Store
Energy due to an object’s temperature.
Thermal stores increase when the object gets hotter and decrease when the object gets cooler.
Elastic Store
Eenergy 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.
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.
How can energy transfers take place?
Energy transfers happen because of: forces doing work, a flow of an electrical current, heating, light radiation, and 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).
When an object is heated what
happens to its internal energy?
When a substance is heated the energy transferred to it increases the internal energy of the system. This either raises the temperature of the system (increases the kinetic energy of the particles) or causes a
change of state (increases the potential energy of the particles)
How is the temperature of a gas
related to the average kinetic energy
of its molecules?
The molecules of a gas are in constant random motion. As the temperature of a gas increases the average kinetic energy of the molecules also increases, this means the particles move around more quickly.
What do we mean by 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 0C
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.
How do you reduce unwanted thermal energy transfers?
Unwanted thermal energy transfers can be reduced e.g. by lubrication (when parts move) and thermal insulation
What does the thermal conductivity of a material tell us?
The thermal conductivity of a material tells us the rate at which energy is transferred through the material when there is a temperature difference either side of it.
What do we mean by rate of cooling?
The rate of cooling of an object is the temperature decrease per second.
