Thermal

Question 1

What is internal energy?

Answer 1

The sum of all of the kinetic energies and potential energies of all its particles.

Question 2

How can the internal energy of a system be increased?

Answer 2

Do work on the system, increase the temperature of the system.

Question 3

When the state of a substance is changed, what happens to the internal energy?

Answer 3

It changes because the potential energy of the system changes while the kinetic energy of the system is kept constant.

Question 4

What is specific heat capacity?

Answer 4

The amount of energy required to increase the temperature of 1kg of a substance by 1 degree C or 1K.

Question 5

What is specific latent heat and what are the two types?

Answer 5

The specific latent heat of a substance is the amount of energy required to change the state of 1kg of a material without changing its temperature. The two types are:
- Specific latent heat of fusion (solid to liquid)
- Specific latent heat of vaporisation (liquid to gas)

Question 6

What does it mean for the gas laws to be empirical in nature?

Answer 6

They are not based on theory, but arose from observation and experimental evidence.

Question 7

What are the 3 gas laws?

Answer 7

• Boyle’s Law
• Charles’ Law
• The Pressure Law

Question 8

What is Boyle’s Law?

Answer 8

When temperature is constant, pressure and volume are inversely proportional.
pV = k

Question 9

What is Charles’ Law?

Answer 9

When pressure is constant, volume is directly proportional to absolute temperature.
V = kT

Question 10

What is the pressure law?

Answer 10

When volume is constant, pressure is directly proportional to absolute temperature.
p = kT

Question 11

What do you add to Celsius to put it in Kelvin?

Answer 11

273

Question 12

What is absolute zero?

Answer 12

-273 degrees C. The lowest possible temperature and the temperature at which particles have no kinetic energy. The volume and pressure of a gas are zero.

Question 13

How can you go between number of mols and number of molecules?

Answer 13

N = n x NA
number of molecules = number of mols x Avagadro

Question 14

What is molar mass?

Answer 14

The mass (in grams) of one mole of a substance.

Question 15

What is the formula for work done?

Answer 15

Work done = pressure x change in Volume

Question 16

What is the area under a pressure/volume graph?

Answer 16

Work done

Question 17

What is Brownian motion?

Answer 17

The random motion of larger particles in a fluid, caused by collisions with surrounding particles.

Question 18

What are the ideal gas assumptions?

Answer 18

1) No intermolecular forces act on the molecules
2) The duration of collisions is negligible in comparison to time between collisions
3) The motion of molecules is random, and they experience perfectly elastic collisions
4) The motion of the molecules follows Newton’s laws
5) The molecules move in straight lines between collisions
6) Size of particles is negligible compared to volume of the container

Question 19

What is the internal energy of an ideal gas, and why?

Answer 19

An ideal gas follows the gas laws perfectly, meaning that there is no other interaction than perfectly elastic collisions between the gas molecules, which shows that no intermolecular forces act between molecules. As potential energy is associated with intermolecular forces, an ideal gas has no potential energy, therefore its internal energy is equal to the sum of the kinetic energies of all its particles.

Question 20

Why wasn’t this model accepted at first?

Answer 20

Knowledge and understanding of any scientific concept changes over time in accordance to the experimental evidence gathered by the scientific community.