14 - Thermal Physics Flashcards Preview

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Flashcards in 14 - Thermal Physics Deck (29)
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1
Q

What is the triple point of a substance?

A

A specific heat and pressure where the substance can exist as a liquid, solid and gas without any net transfer of energy, thermal equilibrium.

2
Q

Describe the energy transfer when a cold object is placed in a warm room.

A

Thermal energy from the air is transferred to the cold object until they are the same temperature.

3
Q

What is thermal equilibrium?

A

When there is no net transfer of energy between two objects because they are the same temperature.

4
Q

What is the 0th law of thermodynamics?

A

If two objects are each in thermal equilibrium with a third, they must all be in thermal equilibrium.

5
Q

How do you convert from Celsius to kelvin?

A

+-273

6
Q

What is 0 degrees Celsius?

A

The freezing point of water.

7
Q

What is 0 degrees Kelvin?

A

Absolute zero - the lowest temperature possible in the universe

8
Q

What is the Kinetic model?

A

A model which describes how all substances are made up of atoms or molecules which are arranged differently depending on the phase of the substance.

9
Q

Describe the molecules in a solid.

A

Regularly arranged
Packed close together
Strong electrostatic forces holding them in place
Can vibrate and have kinetic energy

10
Q

Describe the molecules in a liquid

A

Not regularly arranged
Packed close together
Lots of kinetic energy and weaker electrostatic forces allow them to flow past each other and change position

11
Q

Describe the molecules in a gas

A

Not regularly arranged
Spread out
Negilible electrostatic forces
Able to move around freely

12
Q

What causes density?

A

The size of the space between molecules.

13
Q

Why is ice less dense than water?

A

Because when it freezes, the water molecules are held in a structure where they are further away from each other than when they are a liquid.

14
Q

What is internal energy?

A

The sum of the randomly distributed kinetic and potential energies of molecules in a substance.

15
Q

What causes the potential energy of molecules in a substance?

A

Electrostatic forces between the molecules.

16
Q

What happens to the kinetic energy of molecules at absolute zero?

A

There is no kinetic energy

17
Q

Why is there still internal energy when a substance is at absolute zero?

A

Because even though the particles have no kinetic energy, they still have potential energy as they are held in place by electrostatic bonds.

18
Q

What happens to the kinetic energy when an object is heated to its melting/boiling point?

A

It increases

19
Q

What happens to the potential energy as an object is heated?

A

It increases

20
Q

What happens to the kinetic energy when an object changes state?

A

Nothing - it stays the same

21
Q

What happens to the potential energy when an object changes state?

A

It increases dramatically

22
Q

Describe the potential energy of molecules in a gas

A

0 - the highest possible value

23
Q

Describe the potential energy of molecules in a solid.

A

large negative value

24
Q

Why does the kinetic energy of molecules not change when an object is changing state?

A

Because the energy that is being applied is being used to overcome the electrostatic forces between molecules.

25
Q

What is the specific heat capacity of a substance?

A

The amount of energy required per unit mass to change the temperature of the substance by 1 K.

26
Q

What is the equation for specific heat capacity?

A

E = mc(delta)T

27
Q

What is the specific latent heat of a substance?

A

The amount of energy required per unit mass to change the phase of a substance while at a constant temperature.

28
Q

Specific latent _____ is when a substance changes from a solid to a liquid.

A

Fusion

29
Q

Specific latent _____ is when a substance changes from a liquid to a gas.

A

Vaporisation