particles - physics revision

Question 1

what is brownian motion?

Answer 1

this is evidence that invisible gas particles exist

what it shows is that smoke particles move randomly, because of collisions with other smoke particles resulting a random motion

Question 2

what are the names of the changes of state?

Answer 2

solid to liquid - melting
liquid to solid - solidifying
liquid to gas - boiling / evaporating
gas to liquid - condensing

Question 3

what is boiling?

Answer 3

particles need heat added to change to a gas - at boiling temp

Question 4

what is evaporating?

Answer 4

particles gain enough energy from collisions to change to a gas - happens at any temperature

Question 5

what happens to the temperature when ice changes state?

Answer 5

it stays the same as the energy is being used to push the particles together/apart

Question 6

which state is the densest?

Answer 6

solids

Question 7

which state has the most mass?

Answer 7

solids have more mass than liquids and gases for the same volume

Question 8

what is density?

Answer 8

the measure of compactness of a substance

Question 9

what is the equation for density?

Answer 9

density (kg/m³)= mass (kg)
————–
volume (m³)

Question 10

what does density depend on?

Answer 10

what an object is made of, not the size

Question 11

how do you measure the density of a liquid?

Answer 11

1. put a measuring cylinder on a balance and pour 10ml of the liquid inside, recording its mass
2. put 10ml more in and recorded the total volume and mass
3. repeat until the cylinder is full
4. then find the density using density = mass/volume to find the density of each set of measurements and find the average
   OR
5. weigh the empty cylinder and the full cylinder and subtract them to find the mass
6. then read the cylinder to see the volume of the liquid
   then divide the mass by the volume to find the density

Question 12

how do you find the density of a gas?

Answer 12

1. measure the mass of the full flask
2. measure the mass of the empty flask
3. subtract them to find the mass of the gas
4. using the volume of the gas, divide it by the volume to find the density

Question 13

which state change takes longer- liquid to gas or solid to liquid, and why?

Answer 13

for solid to liquid, you only need to loosen the bonds

for liquid to gas, you need to break the bonds and completely seperate them, so it takes longer

Question 14

what is latent heat?

Answer 14

the energy needed to change the state of 1kg of something

Question 15

what is latent heat of fusion?

Answer 15

the energy needed to change a solid into a liquid

Question 16

what is latent heat of vaporisation?

Answer 16

the energy needed to go from liquid to gas

Question 17

how do you calculate latent heat?

Answer 17

latent heat (J/kg) = energy (J)
————–
mass (kg)