Define internal energy .

Internal energy is the sum of the randomly distributed kinetic and potential energies of the particles in a body.

What causes the kinetic energy and potential energy of the particles that make up a substance's internal energy?

Kinetic energy is due to the speed of the molecules Potential energy is due to the intermolecular forces between molecules, which vary with their separation

Which phase of matter has the highest internal energy, and which has the lowest?

Gases have the highest internal energy and solids have the lowest.

The internal energy of a system can be increased by doing .......... on it or by adding thermal energy to it.

The internal energy of a system can be increased by doing work on it or by adding thermal energy to it.

State four factors that determine the internal energy of a system.

Temperature The random motion of molecules The phase of matter Intermolecular interactions between particles

True or False? The internal energy of an ideal gas includes both the kinetic and potential energy of its particles.

False. An ideal gas has no intermolecular forces , so its internal energy consists only of the kinetic energy of the particles.

State two ways in which the internal energy of a system can decrease.

Losing thermal energy to the surroundings The system doing work on its surroundings

Define the first law of thermodynamics .

The internal energy of a system is increased when energy is transferred to it by heating or when work is done on it .

State two ways the internal energy of a system can be increased.

Work is done on the system (e.g. it is compressed) Thermal energy is transferred to the system by heating

State two ways the internal energy of a system can be decreased.

Work is done by the system (e.g. it expands) Thermal energy is transferred away from the system by heating

For an insulated system, when a gas is compressed, work is done on the gas, which .......... its internal energy.

For an insulated system, when a gas is compressed, work is done on the gas, which increases its internal energy.

What piece of apparatus is commonly used to model a gas doing work on, or having work done on it by, its surroundings?

A gas in a container with a moveable piston .

True or False? When a gas expands and does work on its surroundings, the internal energy of the gas increases.

False. When a gas expands , it does work on its surroundings, which decreases its internal energy.

What principle is the first law of thermodynamics based on?

The principle of conservation of energy .

Define specific heat capacity .

The specific heat capacity of a substance is the amount of thermal energy required to raise the temperature of 1 kg of the substance by 1 °C (or 1 K) without a change of state.

Why do good electrical conductors such as copper and lead heat up and cool down quickly?

They have a low specific heat capacity .

A substance with a .......... specific heat capacity heats up and cools down quickly.

A substance with a low specific heat capacity heats up and cools down quickly.

True or False? The value of Δθ (change in temperature) is different depending on whether it is measured in kelvin or degrees Celsius.

False. A temperature difference is the same size whether measured in kelvin or degrees Celsius, so there is no need to convert between the two.

In a continuous-flow calorimeter experiment, what two quantities are changed between measurements to keep Δθ constant?

The flow rate The potential difference across the heater

What assumption is made about the thermal energy lost to the surroundings in the continuous-flow method?

It is assumed to be constant for both flow rates.

Define the specific latent heat of fusion .

The thermal energy required to convert 1 kg of solid to liquid with no change in temperature.

Define the specific latent heat of vaporisation .

The thermal energy required to convert 1 kg of liquid to gas with no change in temperature.

Why is the specific latent heat of vaporisation of water much greater than its specific latent heat of fusion?

Vaporisation requires the molecules to be completely separated , overcoming all intermolecular forces of attraction, and work is also done against atmospheric pressure , whereas melting only requires the molecules to move far enough apart to flow over each other.

During a change of state, the potential energy of the molecules changes but their .......... energy does not.

During a change of state, the potential energy of the molecules changes but their kinetic energy does not.

True or False? The specific latent heat of fusion applies only to the process of melting.

False. The specific latent heat of fusion applies to both melting a solid and freezing a liquid.

Name the five changes of state.

Melting : solid to liquid Vaporisation (evaporation/boiling): liquid to gas Sublimation : solid to gas Freezing : liquid to solid Condensation : gas to liquid

A LevelPhysicsAQAFlashcardsFurther Mechanics & Thermal PhysicsThermal Energy Transfer

Thermal Energy Transfer (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontInternal Energy
Define internal energy.
FrontInternal Energy
What causes the kinetic energy and potential energy of the particles that make up a substance's internal energy?
BackInternal Energy
Kinetic energy is due to the speed of the molecules
Potential energy is due to the intermolecular forces between molecules, which vary with their separation

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Cards in this collection (30)

Define internal energy.
Internal energy is the sum of the randomly distributed kinetic and potential energies of the particles in a body.
What causes the kinetic energy and potential energy of the particles that make up a substance's internal energy?
- Kinetic energy is due to the speed of the molecules
- Potential energy is due to the intermolecular forces between molecules, which vary with their separation
Which phase of matter has the highest internal energy, and which has the lowest?
Gases have the highest internal energy and solids have the lowest.
The internal energy of a system can be increased by doing .......... on it or by adding thermal energy to it.
The internal energy of a system can be increased by doing work on it or by adding thermal energy to it.
State four factors that determine the internal energy of a system.
- Temperature
- The random motion of molecules
- The phase of matter
- Intermolecular interactions between particles
True or False?
The internal energy of an ideal gas includes both the kinetic and potential energy of its particles.
False.
An ideal gas has no intermolecular forces, so its internal energy consists only of the kinetic energy of the particles.
State two ways in which the internal energy of a system can decrease.
- Losing thermal energy to the surroundings
- The system doing work on its surroundings
Define the first law of thermodynamics.
The internal energy of a system is increased when energy is transferred to it by heating or when work is done on it.
State two ways the internal energy of a system can be increased.
- Work is done on the system (e.g. it is compressed)
- Thermal energy is transferred to the system by heating
State two ways the internal energy of a system can be decreased.
- Work is done by the system (e.g. it expands)
- Thermal energy is transferred away from the system by heating
For an insulated system, when a gas is compressed, work is done on the gas, which .......... its internal energy.
For an insulated system, when a gas is compressed, work is done on the gas, which increases its internal energy.
What piece of apparatus is commonly used to model a gas doing work on, or having work done on it by, its surroundings?
A gas in a container with a moveable piston.
True or False?
When a gas expands and does work on its surroundings, the internal energy of the gas increases.
False.
When a gas expands, it does work on its surroundings, which decreases its internal energy.
What principle is the first law of thermodynamics based on?
The principle of conservation of energy.
Define specific heat capacity.
The specific heat capacity of a substance is the amount of thermal energy required to raise the temperature of 1 kg of the substance by 1 °C (or 1 K) without a change of state.
State the equation linking the change in thermal energy, mass, specific heat capacity and change in temperature.
$Δ Q = m c Δ θ$
Where ΔQ = change in thermal energy (J), m = mass (kg), c = specific heat capacity (J kg^-1 K^-1) and Δθ = change in temperature (K or °C).
Why do good electrical conductors such as copper and lead heat up and cool down quickly?
They have a low specific heat capacity.
A substance with a .......... specific heat capacity heats up and cools down quickly.
A substance with a low specific heat capacity heats up and cools down quickly.
True or False?
The value of Δθ (change in temperature) is different depending on whether it is measured in kelvin or degrees Celsius.
False.
A temperature difference is the same size whether measured in kelvin or degrees Celsius, so there is no need to convert between the two.
In a continuous-flow calorimeter experiment, what two quantities are changed between measurements to keep Δθ constant?
- The flow rate
- The potential difference across the heater
State the final equation used to calculate specific heat capacity from two continuous-flow measurements.
$c = \frac{Q_{2} - Q_{1}}{(m_{2} - m_{1}) Δ θ}$
What assumption is made about the thermal energy lost to the surroundings in the continuous-flow method?
It is assumed to be constant for both flow rates.
Define the specific latent heat of fusion.
The thermal energy required to convert 1 kg of solid to liquid with no change in temperature.
Define the specific latent heat of vaporisation.
The thermal energy required to convert 1 kg of liquid to gas with no change in temperature.
State the equation linking thermal energy, mass and latent heat.
$Q = m L$
Where Q = thermal energy (J), m = mass (kg) and L = latent heat of fusion or vaporisation (J kg^-1).
Why is the specific latent heat of vaporisation of water much greater than its specific latent heat of fusion?
Vaporisation requires the molecules to be completely separated, overcoming all intermolecular forces of attraction, and work is also done against atmospheric pressure, whereas melting only requires the molecules to move far enough apart to flow over each other.
During a change of state, the potential energy of the molecules changes but their .......... energy does not.
During a change of state, the potential energy of the molecules changes but their kinetic energy does not.
True or False?
The specific latent heat of fusion applies only to the process of melting.
False.
The specific latent heat of fusion applies to both melting a solid and freezing a liquid.
State the equation relating the energy change of a colder substance to that of a warmer substance at thermal equilibrium.
$Δ Q_{c o l d e r} = - Δ Q_{w a r m e r}$
Name the five changes of state.
- Melting: solid to liquid
- Vaporisation (evaporation/boiling): liquid to gas
- Sublimation: solid to gas
- Freezing: liquid to solid
- Condensation: gas to liquid

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