Heat and Temperature

Temperature

The measure of the average kinetic energy of all of the particles within an object.

Temperature and Energy

All particles are moving and have kinetic energy.

We can not measure the KE of each molecule, so we take an average of each one.

Taking temperature is finding the average KE of molecules.

Feeling hot or cold is a rough estimate.It is subjective.

Thermometer

A device that measures temperature

Most thermometers rely on the expansion of either fluids or metal to work.

Electric thermometers rely on a change in current.

Temperature Scales

Image/Text/Data from the University of Illinois WW2010 Project

Celsius-Fahrenheit

Celsius – Fahrenheit Conversion Equation

Fahrenheit temperature = (9/5 X Celsius temperature) +

32.0

TF = 9/5t + 32.0

Fahrenheit-Celsius

Fahrenheit – Celsius Conversion Equation

Celsius temperature = 5/9 (Fahrenheit temperature –

32.0)

T = 5/9(TF – 32.0)

Kelvin Based on Absolute

Zero (theoretical)The temperature at

which an object’s energy is minimal

Celsius – Kelvin Conversion EquationKelvin temperature =

Celsius temperature + 273T = t + 273

Relating Temperature to Energy Transfer as Heat

You feel hot and cold because of transfer of energy. Molecules must come into contact with one another.

Hot = absorbing energy from objectCold = releasing energy from object

Heat

The transfer of energy from the particles of one object to those of another object due to a temperature difference between the two objects

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Increases the kinetic energy of the atoms or molecules

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Increases the kinetic energy of the atoms or molecules

Pull atoms or molecules that attract one another farther apart

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Increases the kinetic energy of the atoms or molecules

Pull atoms or molecules that attract one another farther apart

Increases the potential energy of the atoms or molecules

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Increases the kinetic energy of the atoms or molecules

Pull atoms or molecules that attract one another farther apart

Increases the potential energy of the atoms or molecules

Add mass to the object, without changing its temperature

Thermal Energy

Actions that Increase

Thermal Energy

Explanation

Raise the temperature of the object

Increases the kinetic energy of the atoms or molecules

Pull atoms or molecules that attract one another farther apart

Increases the potential energy of the atoms or molecules

Add mass to the object, without changing its temperature

More molecules at the same level of energy means more total energy in the object.

Thermal Energy Equation

Q = m ΔT CQ = change in thermal energy (J)

m = mass (kg)ΔT = change in temperature (˚C)

C = specific heat (J/kg ˚C)

Problem Plug and Chug

Q = 0.5 kg • 60 ˚C • 800 J/kg ˚C mass x change of temp x

specific heat

Q = 24,000 J