thermal properties of matter 🌞

Question 1

define internal energy

Answer 1

internal energy is the sum of internal potential energy and internal kinetic energy

Question 2

describe internal kinetic energy

Answer 2

energy due to the motion of particles - the higher the temperature, the more vigorous the particcle motion

Question 3

describe internal potential energy

Answer 3

due to the stretching and compression of intermolecular bonds - when particles are further apart, their bonds are stretched and they have more internal potential energy (think rubber band) ; same states of matter have the same internal potential energy

Question 4

define specific heat capacity

Answer 4

the amount of thermal energy required to change the temperature of 1KG of a substance by 1C / 1K

Question 5

specific heat capacity formula

Answer 5

Q = mc change in temperature

Question 6

define melting

Answer 6

melting is the process where thermal energy is absorbed by a substance and it changes from solid to liquid state without a change in temperature (same for boiling)

Question 7

define (specific) latent heat of fusion / vapourisation

Answer 7

the amount of thermal energy needed to change 1kg of a substance from solid to liquid state (or vice versa) without a change in temperature

Question 8

why is latent heat of vapourisation higher than latent heat of fusion?

Answer 8

in addition to thermal energy absorbed being used to overcome forces of attraction between particles, thermal energy is also used to do work against atmospheric pressure in order to escape into the surroundings

Question 9

define evaporation

Answer 9

evaporation is the process where a liquid changes into gas without boiling

Question 10

why does evaporation decrease temperature?

Answer 10

particles with higher average kinetic energy at the surface of the water escape into the atmosphere. lowering the average kinetic energy of the particles left behind