thermal physics

Question 1

what is meant by the internal energy?

Answer 1

• sum of all the kinetic energies and potential energies of all its particles

Question 2

how can the internal energy of a system be increased?

Answer 2

• do work on the system
• increase the temperature of the system

Question 3

why does the internal energy change when a state of a substance is changed?

Answer 3

• potential energy of the system changes, while kinetic energy is kept constant

Question 4

what is meant by temperature?

Answer 4

• a measure of the average kinetic energies of the particles

Question 5

what is the specific heat capacity of a substance?

Answer 5

• the amount of energy required to increase the temperature of 1kg of a substance by 1K, without changing its state

Question 6

how can we measure amount of energy required to change the temp of a substance?

Answer 6

Q = mc ^T

m = mass
c = specific heat capacity
^T = change in temp

Question 7

how can we measure the amount of energy required to change the state of a substance?

Answer 7

Q = ml

m = mass
l = specific latent heat

Question 8

what is the specific latent heat of a substance?

Answer 8

• amount of energy required to change the state of 1kg of material, without changing its temperature

Question 9

what are the two types of specific latent heat?

Answer 9

• latent heat of fusion ( solid to liquid )
• latent heat of vaporisation ( liquid to gas )

Question 10

what do the gas laws describe?

Answer 10

• experimental relationship between pressure, volume and temperature for a fixed mass of gas

Question 11

what is Boyle’s Law?

Answer 11

• when temperature is constant, pressure and volume are inversely proportional

pV = k

Question 12

what is Charles’ Law?

Answer 12

• when pressure is constant, volume is directly proportional to absolute temperature

V / T = k

Question 13

what is the Pressure Law?

Answer 13

• when volume is constant, pressure is directly proportional to absolute temperature

P / T = k

Question 14

what is absolute zero?

Answer 14

• lowest possible temperature
• temperature at which particles have no kinetic energy.
• volume and pressure of a gas are zero

Question 15

what is the ideal gas equation?

Answer 15

pV = nRT

p = pressure
V = volume
n = moles
R = 8.31
T = temp

Question 16

what is 1 mole of a substance equal to?

Answer 16

6.02 x 10^23 atoms

Question 17

how can we find number of molecules within a gas?

Answer 17

N = n x 6.02x10^23