Particle model of matter

Question 1

What is internal energy?

Answer 1

energy stored by the particles making up a system

Question 2

What is internal en ergy made up of?

Answer 2

total energy the particles have in their kinetic and potential energy stores

Question 3

What happens when a substance is melting or boiling?

Answer 3

• still putting energy in - internal energy increases - energy used for breaking bonds between particles rather than raising temperature

Question 4

What happens when a substance is condensing or freezing?

Answer 4

• bonds are forming between particles - releases energy - internal energy decreases - temperature doesnt decrease until all the substance has condensed or froze

Question 5

What is latent heat?

Answer 5

energy needed to change the state of a substance

Question 6

What is specific latent heat?

Answer 6

amount of energy needed to change 1kg of a substance from one statea to another without changing its temperature

Question 7

What is the specific latent heat of fusion?

Answer 7

changing between a solid and a liquid

Question 8

What is the specfic latent heat of vaporisation?

Answer 8

changing between a liquid and a gas

Question 9

Formula for specific latent heat?

Answer 9

E = mL (Energy = mass x specific latent heat)

Question 10

What is pressure in gasses?

Answer 10

• as gas particles move around at high speeds, they bang into each other
• when they collide with something they exert a force
• in a sealed container - outward gas pressure is total force exerted by all particles in the gas on a unit area of the container walls

Question 11

Why does increasinsg temperature increase the pressure?

Answer 11

• faster particles - more frequent collisions - increase in net force - larger force for same area = larger pressure

Question 12

Why does increasing volume decrease the pressure?

Answer 12

• particles more spread out - less collisions - less pressure

Question 13

relationship between volume and pressure at constant temperature?

Answer 13

pV = constant

Question 14

How can a change in pressure change the volume?

Answer 14

• pressure of gas causes net outward force at right angles to surface of container
• also force on outside of container due to pressure of gas around it
• if the container can change size e.g. balloon, any change in these presure causes container to compress or expand