p6 - molecules and matter

Question 1

define density

Answer 1

mass per unit volume

Question 2

give units and symbol for density

Answer 2

units: km/m(3) or g/cm(3)
symbol: p

Question 3

how do you know if an object will float in water?

Answer 3

objects with a density less than the density of a given liquid will float in that liquid e.g: objects with a density less than 1000kg/m(3) will float in water

Question 4

what is the volume of a cuboid formula?

Answer 4

a x b x c

Question 5

define melting point

Answer 5

temperature at which a solid changes to a liquid

Question 6

define freezing point

Answer 6

same temperature at which liquid changes to a solid

Question 7

define boiling point

Answer 7

temperatue at which loquid changea to.a gas (same temp as condensation)

Question 8

define the latent heat

Answer 8

the energy transferred to or from a substance

Question 9

define internal energy of a substance

Answer 9

total energy in the kinetic energy store and potential energy store of the particles in the substance

Question 10

where is the kinetic energy from?

Answer 10

due to individual motions relative to eachother

Question 11

where is the potential energy from?

Answer 11

due to individual positions relative to eachother

Question 12

what happens when a substance is heated?

Answer 12

energy of particles increases, so internal energy increases

Question 13

what happens if the total kinetic energy of the particles increases?

Answer 13

temperature of the substance increases

Question 14

what happens if a substance changes state?

Answer 14

potential energy of its particles increases

Question 15

what happens when a solid is heated?

Answer 15

when a solid is heated, the particles’ energy stores increase and they vibrate more

Question 16

what happens when a liquid is heated?

Answer 16

some particles gain enough energy to break away from the other particles and are in a gas state

Question 17

what happens when a gas is heated?

Answer 17

particles gain kinetic energy and move faster

Question 18

what happens when gas molecules are in a box?

Answer 18

• particles in a gas collide with eachother and with the walls of their container
• during these particles exert a force and hence a pressure on the walls of the container

Question 19

define the latent heat of fusion

Answer 19

energy required by a substance to change from a solid to a liquid, with no change in temperature

Question 20

in what conditions is latent heat transferred to surroundings?

Answer 20

if a substance is cooled and changes from a liquid to a solid

Question 21

define the specific latent heat of fusion

Answer 21

energy needed to change 1 kg of the substance from a solid to a liquid, with no change in temperature

Question 22

give equation for specific latent heat of fusion

Answer 22

specific latent (J/kg) = energy (J) / mass (kg)