Matter

Question 1

What is density?

Answer 1

A measure of the ‘compactness’ of a substance, relating its mass to how much space it takes up. It does not vary with size or shape.

Question 2

How is density calculated?

Answer 2

Density = mass / volume
P = m / V
g/cm^3 or kg/m^3 = g or kg / cm^3 or m^3

Question 3

How can you find the density of a solid?

Answer 3

Measure its mass using a balance. (M1)
Fill a bottle with a liquid of known density, place a stopper and dry the outside. Measure its mass. (M2)
Empty the bottle, put the object in, and repeat step 2. Measure its mass. (M3)
Find the mass of displaced water (M2 - (M3 - M1))
Find the volume displaced using the density formula. This equals the object’s volume.
Calculate density using the density formula.

Question 4

What is kinetic theory?

Answer 4

A way of explaining matter using tiny balls to represent particles.

Question 5

What are particles like in a solid?

Answer 5

Strong forces of attraction hold particles close together in a fixed, regular arrangement. Particles have little energy so can only vibrate in fixed positions.

Question 6

What are particles like in a liquid?

Answer 6

Forces of attraction between particles are weaker. Particles are close together but can move past each other and form irregular arrangements. They have more energy so move in random directions at low speeds.

Question 7

What are particles like in a gas?

Answer 7

There are almost no forces of attraction between particles. Particles have more energy than in liquids and are free to move. They travel in random directions at high speeds.

Question 8

What are the names for the different changes of state?

Answer 8

Solid to liquid - melting
Liquid to solid - freezing
Liquid to gas - evaporating
Gas to liquid - condensing
Gas to solid - deposition
Solid to gas - sublimation

Question 9

What is water’s specific heat capacity?

Answer 9

4200 J/kg degreesC

Question 10

What is specific heat capacity?

Answer 10

The amount of energy required to raise 1kg of a substance by 1 degree C.

Question 11

What is the equation for specific heat capacity?

Answer 11

Change in thermal energy = mass x specific heat capacity x temperature change
Q = m x c x theta
J = kg x J/kg degreesC x degreesC

Question 12

How can you find the specific heat capacity of water?

Answer 12

Use a balance to find the mass of the insulating container
Fill it with water and find the mass again, calculate the water’s mass
Use a power supply, a circuit, and an immersion heater to warm up the water. Use E = I x V x t to find the energy transferred over a set time
Measure the temperature change with a thermometer
Find the specific heat capacity

Question 13

Why does temperature not change in a change of state?

Answer 13

Energy is used for breaking intermolecular bonds rather than raising the temperature

Question 14

How can you see how a change of state affects temperature in ice?

Answer 14

Fill a beaker with crushed ice
Put a thermometer in and record the temperature
Use a Bunsen burner to gradually heat the beaker
Record the temperature and state of ice every 20 seconds
Continue this until the water starts to boil
Plot a graph of temperature against time

Question 15

What is specific latent heat?

Answer 15

The amount of energy needed to change 1kg of a substance from one state to another without changing its temperature

Question 16

What are the two types of specific latent heat?

Answer 16

Latent heat of fusion - the latent heat for melting or freezing
Latent heat of vaporisation - the latent heat for evaporating or condensing

Question 17

What is the equation for specific latent heat?

Answer 17

Thermal energy = Mass x Specific Latent Heat
Q = m x L
J = kg x J/kg

Question 18

What creates gas pressure?

Answer 18

Gas particles move around at high speeds, colliding into other particles and things in the way. When they collide, they exert a force and so a pressure. In a sealed container, the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the container walls.

Question 19

What causes gas pressure to vary and why?

Answer 19

Temperature - higher kinetic energies of particles so more frequent and forceful collisions
Volume - particles get closer together and hit the walls more often

Question 20

What is the equation linking pressure and volume?

Answer 20

P1V1 = P2V2
Pressure in Pa or N/m^2
Volume in m^3

Question 21

What is absolute zero?

Answer 21

The temperature at which particles have as little energy in their kinetic stores as possible. It is -273 degrees C or 0 Kelvin

Question 22

How can you change the pressure of a gas in a container?

Answer 22

Heat or cool it

Reduce or increase the volume e.g. in a syringe

Question 23

How does doing work on a gas affect its temperature?

Answer 23

It can increase its energy, which increases its temperature. The gas exerts pressure and so a force and so work has to be done against it. This transfers kinetic energy to it, so increases the internal energy and so the temperature.

Question 24

What is an elastic object?

Answer 24

An object that can be elastically distorted (goes back to its original shape and length after force is removed)

Question 25

What is the elastic limit?

Answer 25

The point at which an object stops distorting elastically and begins to distort inelastically

Question 26

What is the equation for the force on a spring?

Answer 26

Force = Spring constant x Extension
F = k x x
N = N/m x m

Question 27

What does the graph of a spring’s extension look like?

Answer 27

It is linear up until the limit of proportionality, where the graph begins to flatten out. After this is the elastic limit, where the spring becomes permanently stretched.

Question 28

How could you carry out the practical to investigate the link between force and extension in springs?

Answer 28

First do a pilot experiment with an identical spring: load it with masses and plot a force-extension graph. The line should stay straight for at least the first 6 masses, if not use smaller masses.
Actual experiment: measure the spring’s natural length, taking the reading at eye level. Put markers on the bottom and top of the string to make more accurate readings. Add a mass to the string and measure its new length; find the extension. Repeat this process and plot a force-extension graph.

Question 29

What is the equation for energy/work done on a spring?

Answer 29

Energy = 1/2 x spring constant x extension^2
E = 1/2 x k x x^2
J = 1/2 x N/m x m^2

Question 30

What is the equation for pressure?

Answer 30

Pressure = Force / Area
P = F/A
Pa = N/m^2

Question 31

What is the equation for fluid pressure?

Answer 31

Pressure due to a column of liquid = height of the column x density of liquid x gravitational field strength
P = h x rho (like a p) x g
Pa = m x kg/m^3 x N/kg

Question 32

What is upthrust the resultant force to?

Answer 32

Pressure, as pressure increases with depth, so pressure is greater on the bottom of an object than the top. Upthrust is the resultant force upwards.

Question 33

What is upthrust equal to?

Answer 33

The weight of water displaced by the object

Question 34

What makes objects float or sink?

Answer 34

If upthrust is equal to an object’s weight, forces balance and it floats. If an object’s weight is greater than upthrust, the object sinks, so it is to do with density. The denser the object, the more fluid is needed to be displaced for it to float. If it is denser than the fluid, it will sink,

Question 35

What is the relationship between atmospheric pressure and height?

Answer 35

The higher you go, the less the atmospheric pressure, as the atmosphere is less dense, so fewer air molecules are colliding with the surface of the Earth. There are also fewer air molecules, so the weight of the air is less, which contributes to atmospheric pressure, so pressure is less.