Thermal Properties of Matter Flashcards
What is the equation for heat capacity
Q = C*(change in temperature)
Where C is heat capacity and Q is heat(or energy transferred by heating) in J
**capital C
What is the equation for specific heat capacity
Q = mc*(change in temperature)
Where m is mass in kg
c is specific heat capacity in
J kg-1 K-1 or C-1
What is ratio of specific heat capacity to heat capacity
1/mass in kg
Explain latent heat in terms of behaviour of particles during melting
During melting, energy supplied is used to do work against forces of attraction between particles. Particles have a wider range of movement and average distance between the particles increases. This increases internal potential energy of the substance whereas internal kinetic energy remains constant
Explain latent heat in terms of behaviour of particles during boiling
During boiling, energy supplied is used to do work against the forces of attraction between particles so they can move much further apart, as well as do work against atmospheric pressure in order to escape to the surroundings. This increases internal potential energy of substance whereas internal kinetic energy remains constant
Which is higher, latent heat of vapourisation or latent heat of fusion
Latent heat of vapourisation is usually higher than latent heat of fusion as extra energy is needed for molecules to escape into the surrounding atmosphere as vapour
What is the formula for specific latent heat of __
Q = ml
OR L = ml
Where Q is energy transferred by heating and L is latent heat of __
Why is a jet of steam more dangerous than the same mass of boiling water
At same temperature, jet of steam has higher internal energy than the boiling water. When steam condenses, heat released can cause injury.
Why will a hot liquid lose heat throughout a period of time
The liquid has a higher temperature than the surroundings, so there is net transfer of heat from the liquid to the surroundings
Define evaporation
The process where a liquid changes into a gas without boiling. (Boiling and evaporation both involve change of state from liquid to gas and absorb latent heat of vapourisation but are different)
How does evaporation occur
Particles in iquid are moving randomly at different speeds.
Particles at surface of the liquid can escape into the atmosphere if they have sufficient kinetic energy to overcome attractive forces of other liquid particles and do work against atmospheric pressure. Less energetic particles are left behind and average kinetic energy of particles in liquid decreases. Average temperature of the liquid decreases, cooling effect.
What are factors affecting rate of evaporation
Temperature of liquid, area of exposed surface, humidity of surrounding air, motion of air, pressure, nature of liquid
How does temperature increase the rate of evaporation
Higher the temperature, the higher the average kinetic energy of the particles. More particles have minimum amount of kinetic energy required to escape from the surface.
How does area of exposed surface affect the rate of evaporation
The larger the area of exposed surface, the higher the rate of evaporation. There will be more particles at surface that have minimum amount of kinetic energy required to escape into the atmosphere
How does motion of air affect rate of evaporation
Moving air removes the fluid particles as soon as they escape from the surface
