thermal properies

Question 1

define internal energy

Answer 1

internal energy is the energy store made up of the kinetic energy associated with the random motion of all particles and the total potential energy between the particles in the system

Question 2

boiling

Answer 2

• occurs only at boiling point
• vapourisation takes place throughout liquid
• liquid temp remains constant
• rate of vapourisation is fast
• requires a heat source

Question 3

evaporation

Answer 3

• occus at any temp
• vapourisation takes place only at the surface of the liquid
• liquid temp decreases
• rate of vapourisation is low
• does not require a heat source

Question 4

heating curve

Answer 4

during heating energy transferred to the body and particles gain kinetic energy, moving faster. As the average kinetic energy of particles increases, temperature also increases. This is an increase in energy in kinetic store

During melting and boiling, energy transferred to the substance is used to do work against the FOA between particles. Hence potential energy of the particles increase as the average separation between particles increase. As kinetic energy did not change, temperature remains constant. This represents an increase in energy in potential store.

Question 5

cooling curve

Answer 5

During cooling, enerygy is transferred iut of the body and particles lose kinetic energy, moving slower. As the average kinetic energy of the particles decrease, temperature also increases also decreases. This is a decrease in energy in kinetic store

During condensation and solidification, energy is transferred out of the substance. Potential energy of the particles decrease as the average kinetic separation between particles decrease. As kinetic energy did not change, temperature remains constant. This represents a decrease in potential store.