Unit 3 - thermal properties of matter

What is the Si unit for heat?

J

how many J is one cal

4.186

What is thermal energy?

The thermal energy of the system is due to the motion of its atoms and molecules and of the stretching and compressing of spring like molecular bonds

it is a state variable

What is heat?

the energy transferred between the system and the enviroment as they interact.

What is temperature?

state varaible which quantifies how hot or cool a system is

related to the thermal energy per molecule

a temperature difference is required for a thermal interaction

What can happen to a system when you change the thermal energy?

Temperature of the system changes

can undergo a phase change

What is the definition of specific heat capacity?

The amount of energy required to raise the temerature of 1Kg of substance by 1K

What is the equation for specific heat capacity?

Q = Mc temperature change

What is the molar specific heat capacity?

the amount of energy that raises the temperature of 1 mol of substance by 1K

C

What is the equation for molar specific heat?

Q = n C temperature change

What are features of the temperature vs heat graph?

slope = 1/Mc

horizontal line segments - phase changes, thermal energy is breaking bonds

What is the heat of transformation?

the amount of heat energy that causes 1Kg of a substance to undergo a phase change

L

Q = ML

What is the specific heat of fusion?

The heat of transformatio between a solid and a liquid

What is the specific heat of vapourisation?

the heat of transformation between a liquid and a gas

What are the equations for specific heat of transformation?

Q = ± MLf

melt / freeze

Q = ±MLv

boil / condense

What is calorimetry?

Systems are thermally interacting with each other but isolated from everything else

heat energy is transferred from the hotter to the cooler one until a common final temperature is reached

What is energy conversation?

Any energy leaving the hotter system must enter the cooler one

Q1 = -Q2

Qnet = Q1 + Q2 = 0

What are the equations for the specific heat of gases?

Q = nCv temperature change ( constant volume )

Q = nCp temperature change ( constant pressure

What is the first law of thermodynamics?

thermal energy change = Work done + heat energy

What is the equation which links specific heat of gases at constant pressure and volume?

Cp = Cv + 8.31

What are adiabatic processes?

no heat energy is transfered q=0

What are the methods to achieve a adiabatic process?

gas cylinder can be completely surrounded by thermal insulation

the gas can be expanded or compressed rapidly

What is the value of gamma in the adiabatic index for monotomic gas?

1.67

What is the value of gamma in the adiabatic index for diatomic gases?

1.4

What is the equation for the adiabatic index? specific heat ratio

gamma = Cp / Cv

What is the adiabatic relation?

PV^ gamma = constant

What is the equation for the adiabatic in terms of initial and final?

piVi^gamma = pfvf^gamma

What is conduction?

transfer of heat through a material without the movement of the material

energy is passed from one object to another due to a temperature gradient

What is the equation for the law of heat conduction?

DQ/Dt ( rate of heat transfer ) = K x Area/Length x temperature change

What is convection?

The transfer of thermal energy by the motion of fluid

heat rises

What is radiation?

all objects emit energy in the form of radiation, electromagnetic waves

What is the equation for radiation?

Dq/Dt (rate of heat radiated) = emissivity x 5.67×10-8 x surface area x temperature ^4

What is the first law of thermodynamics?

change in thermal energy = w + q