Kientic Theory

Question 1

What is an ideal gas (2)

Answer 1

-an ideal gas is one that is thin enough and for away from condensing that the interaction between molecules is negligible
-ideal gases are so far apart from each other that the interactions between individual particles are negligible this means there are no attractive or repulsive forces between them

Question 2

What does pressure of an ideal gas depend on (3)

Answer 2

Temperature
Number of molecules
Volume

Question 3

State the equation of pressure (2)

Answer 3

Pressure = k x (no of particles x temperature/ volume )

K = 1.38 x 10-23

PV = nRT

Question 4

What happens to the pressure if the volume of ideal gas is held constant (1)

Answer 4

Pressure increases with temperature

Question 5

What happens to the pressure when the volume and temperature is kept constant but more gas is added such as inflating a tire (1)

Answer 5

Pressure increases

Question 6

What happens to pressure when temperature is constant but volume decreases (1)

Answer 6

Pressure increases

Question 7

State the boyles law and state an equation (2)

Answer 7

-the pressure varies inversely with the volume
-the curves of constant temperature are called isotherms

P1V1 = P2V2

Question 8

State the Charles law and give an equation (2)

Answer 8

-the volume of a gas increases with temperature if the pressure is constant

Vi/Ti = Vf/Tf

Question 9

State the formula to calculate the mass of an individual atom (1)

Answer 9

Atomic mass / 6.02 x 10^23

Question 10

State and explain the kinetic theory (3)

Answer 10

-the kinetic theory relates microscopic quantities (position, velocity) to macroscopic one’s (pressure, temperature)
-gas molecule’s always obey newtons law
-collision between gas molecules and walls is elastic

Question 11

Explain how the gas molecules collide (2)

Answer 11

-as a gas molecules moves around they collide with each other and with the walls of the container
-these collisions are elastic (meaning energy and momentum are conserved)

Question 12

Define the pressure of the gas (1)

Answer 12

The pressure of the gas is the result of the average force per unit area due to all collisions with the container walls

Question 13

What does the pressure of gas depend on (3)

Answer 13

-mass
-speed of molecules
-container size

Question 14

What does the maxwell distribution graph explain (1)

Answer 14

-It describes the speeds and kinetic energies of particles in an ideal gas

Question 15

What does the speed depend on (2)

Answer 15

Temperature
Mass of molecule

Question 16

State the formula for average temperature and average KE (1)

Answer 16

1/2mv^2 = K = 3/2kT

Temperature needs to be in kelvin

Question 17

The atmosphere has nitrogen and oxygen, is the rms speed of nitrogen (28g/mol) greater than less than or equal to oxygen (32g/mol) (3)

Answer 17

-since both the molecules are at the same temperature
-they have the same KE
-but nitrogen has a lower mass thus it will have higher speed

Question 18

What is internal energy of a gas and state a formula (1)

Answer 18

-internal energy of an ideal gas is the sum of the KE and PE

U = 3/2 NKT

Question 19

State the equation for monoatomic ideal gas (1)

Answer 19

U = 3/2 NKT

Question 20

How does evaporation occur (2)

Answer 20

-some molecules at the surface of the liquid gain enough KE to overcome the attractive forces within the liquid
-and transition into vapor
-the process of evaporation is faster for lighter molecules

Question 21

How does condensation occur (1)

Answer 21

-molecules in the vapor phase can loose energy and undergo condensation transitioning back into the liquid phase

Question 22

How does dynamic equilibrium take place (3)

Answer 22

-as evaporation and condensation proceed
-the number of molecules transitioning from liquid to vapor equals the number transitioning from vapor to liquid
-equilibrium is reach when the number remains constant

Question 23

When water boils on top of a mountain, does it boil at 100 ?

Answer 23

No
-because the air is thinner, hence less pressure at the top of the mountain thus lower than 100c needed to boil
-a liquid boils at the temperature at which it’s vapor pressure

Question 24

When does a liquid boil (1)

Answer 24

-a liquid boils at the temperature at which it’s vapor pressure equals the external pressure

Question 25

What happens to the process of condensation or evaporation if the container is open (2)

Answer 25

-the vapor will escape and continue to escape without reaching equilibrium
-as the molecules that escape from the liquid are the higher energy ones leaving behind low energy particles

Question 26

Define latent heat and state an equation (3)

Answer 26

-it is the heat that must be added or removed from one kilogram of a substance to convert it from one phase to another
-during this process the temprature remains constant

Heat absorbed or released = mass of substance x specific heat of substance