# P1.2 - Change of State Flashcards

1
Q

define density

A

mass per unit volume

2
Q

what is the equation for density?

A

density = mass(kg)/ volume (m3)

3
Q

what three factors does density depend on?

A
• mass of material
• particle arrangement
• volume
4
Q

explain why the density of a substance in that the solid state is greater than the density of the same substance in the liquid state

A
• there are more particles in the same volume (solid)
• and so the mass is greater
in a liquid, there are less particles in the same volume
so the mass is less
5
Q

why do substances in different matters have different densities?

A

they have different arrangement of particles

6
Q

define temperature

A

the average kinetic energy per particles

7
Q

is temperature a measure of heat energy?

A

no, particles do not know heat energy, only kinetic

8
Q

why does your hand not burn if a spark lands on you?

A
• the mass of the sparkler is very small
• the total energy stored by all the particles is small
• energy is so little, does not burn you
9
Q

what does the energy in a thermal store depend on?

A
• the arrangement of the particles

- how fast they are vibrating or moving

10
Q

what does the energy needed to raise the temperature of an object depend on?

A
• type of material
• the mass of the material
• temp rise
11
Q

what is specific latent heat?

A

the energy transferred when 1kg of a substance changes state

12
Q

what equation is required to calculate the change in thermal energy?

A

mass (kg) x specific heat capacity (j/kg C) x change in temperature (C)

13
Q

what does specific heat capacity show?

A

the amount of energy needed to increase the temperature of 1kg of the substance by 1oC

14
Q

why is water good to use in radiators?

A

because it has a high specific heat capacity, making it resistant to temperature change (so would have a lot of energy to transfer)
- almost 4200J/kg

15
Q

why are saucepans made with low specific heat capacities?

A
• as they need to heat up quickly to heat the food
16
Q

where does the energy from tropical storms come from?

A
• water vapour condensing and transferring energy to its surroundings
17
Q

explain why there is no temperature increase while water is boiling

A
• energy transferred is used to break attractive forces between the water molecules
• internal energy is increasing but temp is not
18
Q

what is the specific latent heat of fusion?

A

(melting)
- the energy transferred when 1kg of a substance changes from the solid state to the liquid state (or vise versa)
WITHOUT CHANGING TEMPERATURE

19
Q

what is the specific latent heat of vaporisation?

A

the energy transferred when 1kg of a substance changes from liquid to gas WITHOUT CHANGING TEMPERATURE

20
Q

what is the equation to calculate the thermal store for a change in state?

A

energy store (J) = mass (kg) x specific latent heat (J/kg)

21
Q

what are the similarities and differences between specific latent heat and specific heat capacity?

A
• they both involve energy changes for 1kg of a substance
• latent heat is about change in state
• heat capacity is about change of temperature
22
Q

what is the law of displacement?

A

an object completely submerged in a fluid will replace an amount of fluid of its own volume

23
Q

what is the force that keeps an object afloat?

A

upthrust

24
Q

what is the equation to calculate specific heat capacity?

A

change in internal energy / mass x change in temperature

25
Q

when a substance changes state, where does the latent heat go?

A

to create or weaken bonds, rather than transfer kinetic energy to the particles

26
Q

what does it mean when a term starts with ‘specific’?

A

means it is measured in kilograms (standardises)

27
Q

what are the units of latent heat of vaporisation?

A

J/Kg

28
Q

What happens to the energy supplied during a change of state at both the melting and boiling points?

A

kinetic energy remains constant while the potential energy increases

29
Q

which two stores of energy are added together to calculate the internal energy?

A

kinetic store + chemical store

30
Q

how does heating a system affect energy stored (in terms of temperature and state)?

A
• increase energy within system
• raises temperature, but remains in same state
• remains same temperature, changes state
• make chemical reactions occur
31
Q

name for when solids turn straight into gases

A

sublimination

32
Q

unit for specific heat capacity?

A

J/Kg°C

33
Q

what does specific heat capacity show?

A

how resistant a material is to temperature change