2 thermal physics

Question 1

Absolute zero

Answer 1

the lowest possible temperature (-273C) where particles have the least kinetic energy

Question 2

Brownian motion

Answer 2

random collisions between microscopic particles in a suspension and the particles of a fluid

Question 3

Convert temperatures between kelvin and degrees celcius

Answer 3

T (in K) = 0 (in C) + 273

Question 4

What causes the changes in pressure of a gas

Answer 4

forces exerted by particles colliding with surface, creating a force per unit area

Question 5

Boyles law

Answer 5

pV = constant
- the product of pressure and volume, for a constant temperature, is constant

Question 6

everyday application and consequences of thermal expansion

Answer 6

• thermal expansion of railway tracks in summer
• thermal expansion of metallic joints in a bridge
• the rise in the level of mercury in a thermometer
• the design of the wings of a jet plane

Question 7

why does the temperature of a substance remain constant during a change of state?

Answer 7

because the supplied energy is not used to increase the kinetic energy of the molecules but to change the binding energies.

Question 8

latent heat

Answer 8

the amount of energy needed to change the state of 1kg of the substance without changing its temperature

Question 9

Define condensation in terms of particles

Answer 9

when gas molecules in the air lose their kinetic energy as they collide with a cool surface. the molecules become closer together and form bonds, becoming a liquid.

Question 10

Define solidification in terms of particles

Answer 10

when liquids lose their kinetic energy, their molecules slow down and form more intermolecular bonds with another. they become locked in place and form a solid.

Question 11

describe evaporation

Answer 11

the escape of more energetic particles from the surface of a liquid

Question 12

why does evaporation cause cooling?

Answer 12

because it requires heat energy. Heat energy is taken away by the particles of a liquid when they vaporise. As heat is taken away from the surroundings for evaporation, it causes cooling.

Question 13

order of the states of matter from which expands the most when heated up

Answer 13

1st gas
2nd liquid
3rd solid
The higher the attraction between the molecules, the smaller the expansion. As this attraction is the most in solids and the least in gases, solids expand the least and gases expand the most on being heated.

Question 14

An increase of temperature of an object is equivilant to an…

Answer 14

increase in the average kinetic energies of all the particles in the object

Question 15

specific heat capacity

Answer 15

the energy required per unit mass per unit temperature increase
c = ∆E/m∆θ

Question 16

describe an experiment to measure the specific heat capacity of a solid and a liquid

Answer 16

calorimeter

Question 17

boiling

Answer 17

liquid –> gas
occurs at a fixed temp
fast process
takes place throughout liquid
bubbles form
temp remains constant
external thermal energy source is required

Question 18

evaporation (comparison)

Answer 18

liquid –> gas
occurs at any temp
takes place at the surface only
no bubbles
temp may change
heat from surroundings is enough

Question 19

thermal capacity equation

Answer 19

C = E/t
energy/temp

Question 20

thermal capacity

Answer 20

amount of heat required to increase the temperature of a substance by 1 degrees celcius

Question 21

linear scale (thermometers)

Answer 21

same distnace moved by thread for same temperature change

Question 22

A second liquid-in-glass thermometer has the same range but it has a greater sensitivity.
Suggest two ways in which the second thermometer might differ from the first

Answer 22

Longer stem
Bigger bulb/more liquid
Narrower bore/thinner thread
Liquid with greater expansitivity