Give an example of work done by a gas.

In a steam engine , expanding steam pushes a piston outwards, doing work on the piston to turn the engine.

What happens to a gas when work is done on it by compression?

The volume decreases as a force pushes the piston inward The molecules move around faster , increasing their kinetic energy This increase in kinetic energy also increases the gas's temperature

When a gas expands, it does work on its .......... by exerting pressure on the walls of its container.

When a gas expands, it does work on its surroundings by exerting pressure on the walls of its container.

True or False? When a gas expands, the work done, W , is positive.

False. When a gas expands , work is done by the gas, so W is negative . W is positive when the gas is compressed (work is done on the gas).

In the first law of thermodynamics equation, what does a negative value of W represent?

Work is done by the system (on its surroundings), so the internal energy decreases.

The first law of thermodynamics states that the increase in internal energy of a system is equal to the sum of the .......... added to the system and the work done on it.

The first law of thermodynamics states that the increase in internal energy of a system is equal to the sum of the thermal energy added to the system and the work done on it.

True or False? The first law of thermodynamics only applies to gases.

False. The first law of thermodynamics applies to all thermodynamic systems , not just gases.

A LevelPhysicsCambridge (CIE)Flashcards16. ThermodynamicsThe First Law of Thermodynamics

The First Law of Thermodynamics (Cambridge (CIE) A Level Physics): Flashcards

Exam code: 9702

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FrontWork Done by a Gas
Define work done by a gas.
FrontWork Done by a Gas
What happens to a gas when work is done on it by compression?
BackWork Done by a Gas
The volume decreases as a force pushes the piston inward
The molecules move around faster, increasing their kinetic energy
This increase in kinetic energy also increases the gas's temperature

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Cards in this collection (11)

Define work done by a gas.
The work done when the volume of a gas changes at constant pressure:
$W = p Δ V$
where p is the external pressure and ΔV is the change in volume.
Give an example of work done by a gas.
In a steam engine, expanding steam pushes a piston outwards, doing work on the piston to turn the engine.
What happens to a gas when work is done on it by compression?
- The volume decreases as a force pushes the piston inward
- The molecules move around faster, increasing their kinetic energy
- This increase in kinetic energy also increases the gas's temperature
When a gas expands, it does work on its .......... by exerting pressure on the walls of its container.
When a gas expands, it does work on its surroundings by exerting pressure on the walls of its container.
True or False?
When a gas expands, the work done, W, is positive.
False.
When a gas expands, work is done by the gas, so W is negative. W is positive when the gas is compressed (work is done on the gas).
Define the first law of thermodynamics.
The increase in internal energy of a system is equal to the sum of the thermal energy added to the system and the work done on it:
$Δ U = q + W$
In the first law of thermodynamics equation, what does a positive value of q represent?
Heat is added to the system.
In the first law of thermodynamics equation, what does a negative value of W represent?
Work is done by the system (on its surroundings), so the internal energy decreases.
The first law of thermodynamics states that the increase in internal energy of a system is equal to the sum of the .......... added to the system and the work done on it.
The first law of thermodynamics states that the increase in internal energy of a system is equal to the sum of the thermal energy added to the system and the work done on it.
True or False?
The first law of thermodynamics only applies to gases.
False.
The first law of thermodynamics applies to all thermodynamic systems, not just gases.
A liquid vaporises at constant pressure, absorbing 3.48 × 10⁴ J of heat and doing 6.07 × 10³ J of work on its surroundings as it expands. Calculate the change in internal energy of the system.
$Δ U = q + W$
W is negative since the gas expands (does work on its surroundings):
$Δ U = (3.48 \times 10^{4}) + (- 6.07 \times 10^{3}) = 2.9 \times 10^{4} J (2 s.f.)$

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