molecules and matter (required practical)

Question 1

what is density?

Answer 1

how much mass in contained in a specific volume of a material.

Question 2

what is the formula for density?

Answer 2

density kg/m³ = mass kg ÷ volume m³

Question 3

rank the 3 states of matter in order of density.

Answer 3

1. solid. strong forces hold particles close together in a regular arrangement so they generally have the highest density
2. liquid. weaker forces hold particles in an irregular arrangement so they are less dense than solids
3. gas. almost no force between particles so they freely move and are less dense than liquids

Question 4

how do you find the density of a regular solid? (required practical)

Answer 4

1. use a balance scale to get the mass of the object.
2. use a ruler to measure the height width and length to calculate volume.
3. density = mass ÷ volume

Question 5

how do you find the density of an irregular solid? (required practical)

Answer 5

1. use a balance scale to get the mass of the object.
2. fill a eureka can to just below the spout.
3. hold a measuring cylinder below the spout and place the object in the can.
4. find the volume of the water displaced into the cylinder.
5. density = mass ÷ volume of water

Question 6

how do you find the density of a liquid? (required practical)

Answer 6

1. place a measuring cylinder on a balance scale and zero the scale.
2. pour 10ml of the liquid into the cylinder and note the mass.
3. repeat this until all the liquid is in the cylinder and has been weighed.
4. for every measurement calculate the density with density = mass ÷ volume.
5. find the average density.

Question 7

what is internal energy?

Answer 7

the total energy stored by particles in a system. kinetic and potential energy stores

Question 8

what are the changes of state between gas ⇌ liquid? (2)

Answer 8

evaporating.
condensing.

Question 9

what are the changes of state between liquid ⇌ solid? (2)

Answer 9

freezing.
melting.

Question 10

what is the change of state from solid to gas? (2)

Answer 10

sublimating.

Question 11

what happens to the mass in a change of state?

Answer 11

mass is conserved. stays the same

Question 12

what happens to the temperature of a substance when it is melting or evaporating?

Answer 12

the temperature stays the same. energy is being used to break bonds instead of changing the temperature

Question 13

what happens to the temperature of a substance when it is condensing or freezing?

Answer 13

the temperature stays the same. energy is being released to form bonds but the temperature doesn’t decrease

Question 14

what is the energy needed to change state called?

Answer 14

latent heat.

Question 15

what is latent heat?

Answer 15

the energy need for 1kg of a substance to change state.

Question 16

what is the latent heat needed for melting or freezing called?

Answer 16

latent heat of fusion.

Question 17

what is the latent heat needed for evaporating or condensing called?

Answer 17

latent heat of vaporisation.

Question 18

what is the formula for latent heat?

Answer 18

energy jules = mass kg x specific latent heat j/kg

Question 19

what is pressure?

Answer 19

the force exerted over an area.

Question 20

how do gas particles create pressure?

Answer 20

gas particles collide with eachother and other objects exerting a force. the outwards force is the total force of all the particles

Question 21

how do you increase the pressure of a gas? (2)

Answer 21

1. heating. increase the speed of particles so collisions are more frequent increasing total force
2. decrease the volume of the gas. the particles have less space and collisions are more frequent

Question 22

why are pressure and volume inversely proportional?

Answer 22

when the volume increases the pressure decreases.

Question 23

what can a difference in pressure between 2 sides of an object cause? e.g. a balloon

Answer 23

expansion.
compression.

Question 24

what happens if you do work on a gas?

Answer 24

the temperature increases. in a bike pump the gas resists the plunger and so to pump you have to do work against this force