Unit B:Gases: The Kinetic Molecular Theory/ Physical Properties of Gases

Question 1

The kinetic molecular theory is used to explain natural events in science, such as how water evaporates, and how food colouring diffuses in water. It has three main points:

Answer 1

1. Gas molecules perform a random, constant motion. The molecules travel in straight lines(random walk) until collisions with other molecules( gas or container) occur.
2. Ideal gas molecules are point masses(a mass that takes up no space).
3. Gas molecules only interact with other gas molecules or the container through elastic collisions. The molecules do not perform attractive or repulsive forces on each other.

Question 2

Real gases approximate-

Real gases interact-

Answer 2

Real gases approximate point masses when the volume of the container is much greater than the volume of the gas molecules themselves.
Real gases interact with each other; the is often an attractive force among the molecules.

Question 3

A gas is empirically defined as a substance that fills and assumes the shape of its container, diffuses rapidly, and mixes. The physical properties of gases are:

Answer 3

1. Gases are compressible, the volume increases as the pressure decreases.
2. Gases expand as the temperature is increased if the pressure remains constant.
3. Gases have a very low resistance to flow.
4. Gases have much lower densities than solids or liquids.
5. Gases mix evenly and completely, in the same container, that is they are miscible with each other.

Question 4

What is pressure?

Answer 4

Pressure: Force per unit area, the SI units are kilopascals(kPa) but might be measured in atmospheric pressure(atm).

Question 5

What is atmospheric pressure:

Answer 5

The pressure exerted by the air, at sea level this is 101 kPa. This value is used as a basis to define one standard atmosphere(1 atm) or standard pressure.

Question 6

What is 1 atm in Kpa and mmHg?

Answer 6

1 atm = 101.325kPa = 760mmHg

Question 7

What is standard ambient pressure?

Answer 7

100 kPa.

Question 8

What is STP?

Answer 8

Standard conditions for gases.

237.15K at 1 atm or 760mmHg or 101.325kPa.

Question 9

What is SATP?

Answer 9

Standard ambient temperature and pressure.

25 degrees celsius/298.15 at 100kPa/1 bar