Thermal Physics

Question 1

What is room temperature

Answer 1

25 degrees Celsius

Question 2

What is absolute zero

Answer 2

-273 Celsius or 0K

Question 3

Describe the compressibility of a liquid

Answer 3

The liquid itself is not compressible, rather the air in between

Question 4

What is evidence for the kinetic molecular model of matter

Answer 4

The random motion of particles in suspension. Ie. Brownian motion which can be described in terms of molecular bombardment

Question 5

What is specific latent heat

Answer 5

The amount of energy required to change the state of 1kg of a material without changing its temperature

Question 6

What is boiling point determined by

Answer 6

The atmospheric pressure

Question 7

Describe the difference between boiling and evaporating

Answer 7

Boiling occurs only at boiling point, throughout the liquid and the rate is dependent on the heat supply
Evaporation occurs at the surface of the liquid,through a range of temperatures and the rate depends on humidity, surface area and air movement above the surface

Question 8

Are pressure and volume inversely or directly proportionate

Answer 8

Inversely

Question 9

What happens to the potential energy as particles move further apart

Answer 9

It increases

Question 10

Consequences of thermal expansion (3)

Answer 10

Railway lines and cement and buildings buckle unless they have expansion joints.
Hot water pipes would break if they didn’t have an expansion joint in the form of a loop
Expansion in a pendulum during warm weather slows the clock (thus they have adjusting screws)

Question 11

Application of thermal expansion

Answer 11

Bimetallic strips. Two strips of metal, often copper and iron. When heated copper expands more than iron causing the iron strip to bend with copper on the outside

Switches in electrical circuits

Question 12

Distinguishing properties of solids (4)

Answer 12

Incompressible
Keep their shape
Cannot flow
High density

Question 13

Distinguishing properties of liquids (4)

Answer 13

Incompressible
Take shape of bottom of container
Flow
High density

Question 14

Distinguishing properties of gas

Answer 14

Compressible
Fill volume of container
Flow
Low density

Question 15

Particle structure of solids in terms of arrangement, separation and motion of the particles

Answer 15

Vibrate around a fixed/central position and do not swap positions as there are strong forces between molecules. The particles are arranged in a lattice and there is minimal space between particles

Question 16

Particle structure of liquid in terms of arrangement, separation and motion of the particles

Answer 16

Fluid shape (takes shape of container)
Particles are close together, so have a fixed volume and can only be compressed slightly
Particles are loosely packed together and irregularly arranged
Liquid particles can move randomly in any direction, provided the particles stay close to one another - they can vibrate and slide over each other

Question 17

Particle structure of gas in terms of arrangement, separation and motion of the particles

Answer 17

Randomly arrangement, unrestricted by each other so have completely random motion in any and all directions .

Question 18

Relationship between motion of particles and temperature

Answer 18

Average kinetic energy is related to temperature, meaning the higher the temperature, the more kinetic energy and the more, quicker movement of particles. Particles have the least movement at 0K / -273*C

Question 19

Boyle’s law

Answer 19

Pressure and volume of a gas
The less volume the more collisions between the particles and the wall of the containers. When they collide they exert a force meaning more collisions = more force causing pressure to increase
PRESSURE OF GAS IS INVERSELY PROPORTIONAL TO VOLUME

Question 20

Evidence for the kinetic particle model of matter

Answer 20

Random motion of particular in a suspension. This (brownian) motion seen in dust + pollen is explained in terms of random molecular bombardment, massive particles moved by light, fast moving molecules of air.

Question 21

What affects the properties of solids, liquids and gases

Answer 21

Forces, distances between particles (atoms, molecules, ions and electrons) and the motion of particles

Question 22

How may microscopic particles be moved

Answer 22

Through collisions with light fast-moving molecules

Question 23

Internal energy

Answer 23

Sum of potential and kinetic energies of the particles (atoms/molecules/ions) of a body. Thermal energy transferred to/from a body results in a change in internal energy. More distance means more potential energy

Question 24

What does the amount of expansion of solids/liquids/gases depend on

Answer 24

The strength of the bonds between particles and the temperature increase

Question 25

Expansion in solids

Answer 25

When heated, kinetic energy increases causing particles to vibrate faster and over a larger distance. Forces the particles exert on each other overcome the forces of the bonds, forcing them further apart (expansion). This distancing is minimal as the bonds are very strong

Question 26

Expansion in liquids

Answer 26

More than in solids as the forces of cohesion are weaker

Question 27

Expansion in gases

Answer 27

Forces are very small, resulting in a lot of expansion as the molecules are able to move faster at higher temperatures, increasing the magnitude of the forces during collisions

Question 28

Describe an increase in temperature of an object

Answer 28

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

Question 29

What causes the cooling of a liquid

Answer 29

Evaporation

Question 30

Specific heat capacity

Answer 30

Amount of energy required to raise the temperature of 1kg of a substance by 1*C

Question 31

Unit of specific heat capacity

Answer 31

J kg-1 C-1 J kg-1 K-1

Question 32

Experiment to find specific heat capacity of metal

Answer 32

Place immersion heater into central hole at top of block Place thermometer into smaller hole with oil to ensure thermometer is surrounded by hot metal Fully insulate the block by loosely wrapping with cotton wool Record temperature Connect heater to power supply and turn off after 10 minutes, then record the highest temperature it reaches as it cools

Question 33

Melting and boiling

Answer 33

Energy input without change in temperature

Question 34

When does condensation occur

Answer 34

When gas molecules in the air lose their kinetic energy as they collide with a cool surface. They become closer and form bonds to become a liquid

Question 35

Factors that affect evaporation (3)

Answer 35

Temperature Surface area Air movement

Question 36

Cooling of an object in contact with an evaporating liquid

Answer 36

As the liquid cools, the solid does too. Used in fridges and air conditioning units

Question 37

Temperature

Answer 37

The average kinetic energy of molecules in a substance

Question 38

Conduction in non-metal

Answer 38

Transfer of heat through vibration of atoms with nearby atoms

Question 39

Describe experiments to demonstrate the properties of good and bad conductors of heat.

Answer 39

Take rods of different materials with the same dimensions (same length and cross-sectional area), and attach a drawing pin to the end of each using the same mass of wax. Using a container with four rubber-lined holes in the side. Insert the rods through the holes, pushing them in the same amount. Fill the container with boiling water and start the stopwatch. Time how long it takes the drawing pin to fall off each rod and compare the times. The rod that allowed the pin to fall off fastest is the best conductor.

Question 40

Thermal conduction in metals

Answer 40

The transfer of heat due to vibration of atoms with nearby atoms and free moving electrons which heat farther atoms

Question 41

Convection

Answer 41

The transfer of heat in liquids and gases

Question 42

Best emitter and absorber of infrared rays

Answer 42

Dull black

Question 43

Worst emitter and absorber of infrared rays

Answer 43

Shiny white

Question 44

Radiation

Answer 44

Infrared waves emitted from the surface of all objects that, the rate of emission increases as the surface temperature increases and this method of thermal energy transfer does not require a medium

Question 45

what happens to an object if the rate at which it receives energy is less or more than the rate at which it transfers energy away from the object

Answer 45

If it is less, then the temperature of the object will cool down More, it will increase

Question 46

What needs to happen for an object to be at a constant temperature

Answer 46

it needs to transfer energy away from the object at the same rate that it receives energy

Question 47

how is the temperature of the Earth affected

Answer 47

by factors controlling the balance between incoming radiation and radiation emitted from the Earth’s surface

Question 48

Everyday consequences of thermal conduction, convection and radiation (3)

Answer 48

Handle of a pan getting hot Metal roof of a house getting hot Rubber soles melting next to a radiator

Question 49

Everyday applications of conduction, convection and radiation (3)

Answer 49

Heating kitchen pans to cook with Heating a room by convection Refrigerators Greenhouses

Question 50

Explain some of the complex applications and consequences of conduction, convection and radiation where more than one type of thermal energy transfer is significant (2)

Answer 50

Radiator in a car A fire burning wood or coal