SOLIDS, LIQUIDS AND GASES

Question 1

relationship between density, mass and volume:

Answer 1

density= mass/ volume

Question 2

relationship between pressure, force and area:

Answer 2

pressure= force/ area

Question 3

where does the pressure at a point in a gas or liquid at rest act?

Answer 3

equally in all directions

Question 4

relationship between pressure difference, height, density and gravitational field strength:

Answer 4

pressure difference= height x density x gravitational field strength

Question 5

P2 why will a heating system change the energy stored within the system?

Answer 5

a substance must absorb heat energy so that it can melt or boil

Question 6

P2 arrangement and motion of particles in a solid:

Answer 6

• tightly packed
• fixed pattern
• vibrate about fixed positions

Question 7

P2 arrangement and motion of particles in a liquid:

Answer 7

• tightly packed
• can slide over each other

Question 8

P2 arrangement and motion of particles in a gas:

Answer 8

• free to move
• spread out
• move with rapid, random motion

Question 9

P2 what is specific heat capacity?

Answer 9

• energy required to change the temperature of an object by one degree celsius per kilogram of mass

Question 10

P2 relationship between change in thermal energy, mass, specific heat capacity, change in temperature:

Answer 10

Change in thermal energy [J] = Mass [kg] x Specific heat capacity [J/kg 0C] x Change in temperature [0C]

Question 11

why do gases exert a pressure on the walls of a container?

Answer 11

• they have a random motion
• exert a force and hence a pressure on the walls of a container

Question 12

what is the absolute 0 of temperature?

Answer 12

-273 degrees celsius

Question 13

what is a kelvin?

Answer 13

-273 degrees celsius

Question 14

why does an increase in temperature result in an increase in the average speed of gas molecules?

Answer 14

• their kinetic energy increases

Question 15

what is a Kelvin temperature of gas proportional to?

Answer 15

• the average kinetic energy of its molecules

Question 16

why is, for a fixed amount of gas:
- pressure and volume at a constant temperature
- pressure and Kelvin temperature at constant volume

Answer 16

• As you heat the gas, the kinetic energy of the particles increases, and thus so does their average speed.
• This means more collisions per second with the walls, and they exert a larger force on the wall.
• This causes in the total pressure being exerted by the particles to rise.
• If temperature is constant, the average speed of the particles is constant.
• If the same number of particles is placed in a container of smaller volume they will hit the walls of the container more often.
• More collisions per second means that the particles are exerting a larger force on the wall over the same time, so average force exerted on the walls has increased.

Question 17

relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume:

Answer 17

P1/T1 = P2/T2

Question 18

relationship between the pressure and volume of a fixed mass of gas at constant temperature:

Answer 18

p1V1=p2V2

Question 19

how to convert kelvin into celsius:

Answer 19

C = K- 273

Question 20

what is Brownian motion?

Answer 20

• large particles move randomly
• because tiny particles are hitting them
• tiny particles are not visible

Question 21

example of Brownian motion:

Answer 21

pollen suspended in water

Question 22

using ideas about particles, explain how air inside a container exerts pressure (3 marks):

Answer 22

• collide with one another and walls of the container
• (bombarding particles) exert a force on walls of container
• pressure is force on an area