Thermodynamics Flashcards

1
Q

Define internal energy of a substance

A

The sum of the random distribution of kinetic energies and potential energies of all atoms in a substance.

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2
Q

When does internal energy change?

A

When temperature is changed, the kinetic energy of the atoms change.
When the state of the substance is changed, the potential energy of the atoms change.

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3
Q

Define specific heat capacity

A

The energy required to change the temperature of a unit mass by a unit temperature change.

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4
Q

How do you go from °C to K?

A

T/k = θ/°C + 273

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5
Q

Why is the specific heat capacity of water useful for a central heating system?

A

The specific heat capacity of water is 4200Jkg^-1k^-1. For 1kg of water, 4200J of energy is needed to increase the temperature by 1°C. The water can absorb or emit a high value of energy for a small temperature change.

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6
Q

Define thermal equilibrium

A

When two substances in thermal contact are at the same temperature and there is no further heat flow.

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7
Q

What is the equation for thermal equilibrium?

A

Heat energy lost by hotter substance = heat energy gained by the colder substance

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8
Q

Define specific latent heat

A

The energy required to change the state of a unit mass at constant temperature.

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9
Q

Define specific latent heat of fusion

A

The energy required to change the state of a unit mass from solid to liquid at constant temperature.

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10
Q

Define specific latent heat of vaporisation

A

The energy required to change the state of a unit mass from liquid to gas at constant temperature.

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11
Q

Define Boyle’s Law

A

For a fixed mass of gas at constant temperature, pressure is inversely proportional to volume.

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12
Q

Define the Pressure Law

A

For a fixed mass of gas at constant volume, pressure is directly proportional to absolute temperature.

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13
Q

Define absolute zero

A

The coldest possible temperature where a substance has minimum internal energy.

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14
Q

Define Charles’ Law

A

For a fixed mass at constant pressure, volume is directly proportional to absolute temperature.

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15
Q

How many atoms or molecules are in a mole of a substance?

A

Avogadro’s constant (6.02x10^23)

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16
Q

What does n stand for in PV=nRT

A

n - number of moles

17
Q

What is the formula for the mass of a gas?

A

Mass of a gas = number of moles x mass of 1 mole (molar mass)

18
Q

What is the mass of one mole also know as?

A

The molar mass

19
Q

What is the formula for the number of atoms or molecules in a gas?

A

Number of atoms of molecules in a gas = number of moles x Avogadro’s constant

20
Q

What happens to the smoke particles in the Brownian motion experiment?

A

The smoke particles move randomly and continuously.
The smoke particles constantly change direction and speed.

21
Q

What are conclusions about air molecules from the Brownian motion experiment?

A

The air molecules bombard the smoke particles from all sides.
The air molecules move randomly and continuously.
The air molecules are too small to be seen through a microscope.

22
Q

How does a gas exert a pressure on the walls of a container?

A

A molecule collides with the walls and rebounds so momentum changes direction. (From Newton’s Second Law) the rate of change of momentum means a force is exerted on the molecule. (From Newton’s Third Law) there is an equal and opposite force in the wall. Pressure = sum of forces on a wall from many molecules / area.

23
Q

Define internal energy of an ideal gas

A

The sum of the random distributions of kinetic energies of all molecules in a gas.