Particle model

Question 1

What does the kinetic theory state?

Answer 1

Everything is made of many small particles which are constantly moving

Question 2

Describe the arrangement for solids

Answer 2

Forces of attraction hold the particles very closely together - they vibrate but do not move around which explains why solids can keep their shape but not be compressed

Question 3

Describe the arrangement for liquids

Answer 3

• Particles are moving faster and so forces of attraction between the particles are not strong enough to keep the fixed position
• the particles can move past each other so liquids flow and take shape of their container
• the particles are still close together so cannot be compressed

Question 4

Describe the arrangment for gases

Answer 4

• particles are far apart and moving around quickly

- gases are compressible and expand to fill their container

Question 5

Explain how a state change is a physical change

Answer 5

The particles end up in a different arrangement, but the number of particles does not change (mass conservation) - no new substances are made, and the substance can recover its original properties

Question 6

What is the density of a substance

Answer 6

The mass of a certain volume of the substance

Question 7

When is a substance the most and least dense?

Answer 7

Most - solid

Least - gas

Question 8

How do you investigate the densities of solids and liquids

Answer 8

1. put an empty beaker on a balance and set it to 0
2. use a measuring cylinder to measure 50cm3 of a liquid and pour it into a beaker and write down the reading on the balance which is the mass of 50cm3
3. find the mass of the solid and write it down
4. stand a displacement can on the bench with its spout over a bowl and fill it with water until the water just starts to come out the spout
5. hold a cylinder under the spout and carefully drop the solid into the can and if it floats, push it down (your finger shouldn’t be in the water though)
6. stand the cylinder on the bench and read the volume of the water collected which is the same as the volume of your solid

Question 9

What is the formula for density?

Answer 9

density = mass / volume

Question 10

What is thermal energy

Answer 10

Energy transferred to a system by heating that is stored in the movement of particles

Question 11

What happens to the vibrations of the particles when the thermal energy increases?

Answer 11

The vibrations increase

Question 12

What is the temperature a measure of?

Answer 12

A measure of the movement of the particles

Question 13

How do you maintain a store of thermal energy

Answer 13

The amount of energy transferred to the surroundings by heating needs to be reduced by surrounding the warm object by insulating materials such as wool, foam or bubble wrap

Question 14

What does the amount of thermal energy stored in an object depend on?

Answer 14

• its temperature
• its mass
• material its made of

Question 15

What is the specific heat capacity of an material

Answer 15

The amount of energy it takes to increase the temperature of 1kg of the substance by 1 degree

Question 16

When does the temperature change during a state change?

Answer 16

The temperature increases as more energy is being supplied to the solid, but while it’s melting, the temperature stays constant because the energy is being used to break the arrangement

Question 17

What is the specific latent heat

Answer 17

the amount of energy it takes to make 1kg of a substance, change state

Question 18

Which needs more energy, evaporation or melting?

Answer 18

Evaporation

Question 19

How do you melt ice before finding the specific heat capacity

Answer 19

• Put a boiling tube full of crushed ice into a heatproof beaker and note the temperature
• Put the beaker on a tripod and gauze and pour hot water from a kettle and keep it warm using a bunsen burner
• Measure the temperature every minute and stop after three minutes when all the ice is melted
• make sure you have noted the time when the ice appeared to start melting and when it has now fully melted

Question 20

How do you take the measurements for calculating the specific heat capacity

Answer 20

• put a polystyrene cup in a beaker on a battery scale balance note it down and then change it to 0
• add water to the cup and measure the mass
• put a thermometer in the cup and use a 12V electric heater making sure its fully submerged under the water and connect it to a joulemeter
• record the water temperature, turn on the heater and then gently stir the water using a thermometer
• after 5 minutes, check the temperature and record it also checking the joulemeter

Question 21

What is the temperature of a gas a measure of?

Answer 21

The average kinetic energy of the particles in the gas - the faster the average speed, the higher the temperature (heating the gas increases the kinetic energy and so the temperature increases)

Question 22

What is the pressure of gas based on?

Answer 22

Due to forces on the walls of a container caused by the moving particles hitting the walls - the faster the particles are moving, the more frequent the collisions will be and so exert more force when they collide

Question 23

What does increasing the temperature of a gas do?

Answer 23

Increases the speed of the particles and so increases the pressure

Question 24

What is the unit for pressure

Answer 24

Pascals (1Pa = 1 N/m^2)

Question 25

What is absolute zero

Answer 25

The lowest temperature that is theoretically possible at which the motion of particles which constitutes heat would be minimal

Question 26

What is the temperature for absolute zero

Answer 26

-273.15 degrees C

Question 27

What does the Kelvin temperature scale measure

Answer 27

measures temperatures relative to absolute zero (units are kelvin) - absolute zero is 0K on the scale

Question 28

How do you convert Kelvin to Celcius and vice versa

Answer 28

Kelvin to Celcius = subtract 273 | Celcius to Kelvin = add 273

Question 29

What is gas pressure?

Answer 29

The force exerted by gas particles colliding with the wall of their container. Gas pressure is the force exerted by a gas on a specific area.

Question 30

How does gas pressure increase?

Answer 30

When the gas particles in a larger volume are forced into a smaller volume and so hit the walls more often and so the force on the walls increases

Question 31

How does work done tie into gas pressure?

Answer 31

For example, when using a bicycle pump, each time you push the pump handle, the force is transferring energy to the gas inside the pump (work done)

Question 32

What does elastic and inelastic meaning

Answer 32

Elastic - the object will return to its original shape when forces are removed Inelastic- they will keep their new shape after the forces are removed

Question 33

Give an example of an object which behaves elastically with small forces but with larger forces behaves inelastically

Answer 33

Metal springs (behave elastically) but if they are stretched too big they become permanently damaged

Question 34

What is the extension of a spring (or another object)?

Answer 34

The change in length when forces are applied

Question 35

What is the relationship between the extension and force

Answer 35

They are directly proportioanl - if the extension doubles, the force doubles

Question 36

When does the relationship between the extension and force become non-linear?

Answer 36

When the spring is stretched too far

Question 37

What is the spring constant?

Answer 37

The force needed to produce an extension of 1 metre

Question 38

What is pressure a measure of?

Answer 38

The force on a unit of surface area where the force is normal (at right angles) to the surface

Question 39

What is the pressure at sea level?

Answer 39

100 000 Pa

Question 40

What does the pressure of a fluid depend on?

Answer 40

The depth of the fluid - the deeper you are the more weight of the fluid there is above you to exert pressure (e.g when you are at the bottom of the ocean, the pressure is high and when you are at the top of a mountain the air pressure decreases as there is less air above you)

Question 41

What is atmospheric pressure due to?

Answer 41

The whole depth of the atmosphere above you

Question 42

If you dive 10 underwater, how much pressure will you feel compared to at the surface

Answer 42

Double the pressure than at the surface

Question 43

How many more times is water denser than the air at sea level

Answer 43

800

Question 44

What is upthrust in a fluid due to?

Answer 44

Due to the difference in pressure above and below the object

Question 45

What must happen to the upthrust in order for an object to float

Answer 45

The upthrust must be equal to the weight of the block

Question 46

What happens to objects which are not equal in upthrust and weight in the block

Answer 46

They sink