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Thermal Physics

Quick questions on Internal energy and the first law of thermodynamics: H2 Physics Thermal Physics

6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is internal energy?
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The internal energy UU of a system is the sum of the random kinetic and potential energies of all its molecules. The kinetic part is due to molecular motion (translational, and for molecules also rotational and vibrational); the potential part is due to intermolecular forces.
What is the first law of thermodynamics?
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The first law states that the increase in internal energy of a system equals the thermal energy supplied to it plus the work done on it:
What are work done by an expanding gas?
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When a gas at pressure pp expands by a small volume ΔV\Delta V at constant pressure, the work done by the gas is:
What is q1?
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Define the internal energy of a system and state what it depends on for an ideal gas. [2 marks]
What is q2?
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A gas releases 80 J80\ \text{J} of heat to the surroundings while 120 J120\ \text{J} of work is done on it. Find the change in internal energy. [2 marks]
What is q3?
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Explain why the temperature of a gas rises when it is compressed adiabatically. [3 marks]

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