Temperature, Heat, and Laws of Thermodynamics

Kinetic Energy Tie In• There were 4 main types of kinetic

energy that we went over. • Translational KE• Rotational KE• Mechanical KE• Vibrational KE

• Translational KE is when an object is moving forward. • Rotational KE is when an object is

spinning. • Mechanical KE is when the parts of

something are moving together.• Vibrational KE is when an object is

moving in a repetitive back and forth motion, like shaking.

• Translational and rotational KE happen on a larger scale. • The large object moves from point A to

point B. We covered most of that in the first half of the unit. • Mechanical KE happens on a smaller

scale. • Vibrational KE happens mostly on a

microscopic or molecular level.

• We’ll mostly be looking at Vibrational KE for the rest of the unit.

• Temperature is the measure of average kinetic energy of matter.

Temperature• We can say temperature is a

measure of an object’s hotness or coldness.• It is NOT a measure of heat. But it

can be used as an indicator of heat or internal energy.

• The faster the molecules are vibrating and moving, the hotter the object feels. • This gives it a higher temperature. • The slower the molecules are vibrating

and moving, the colder the object feels. • This gives it a lower temperature. • TL;DR – The faster the molecules are

moving, the higher the temperature.

• Another factor for temperature is how crowded the molecules are together.

• Think about what happens during a fire or bomb drill here at the school, or in your cramped classrooms.

• The closer the molecules, the more they’ll bump into each other. • That increased molecular friction

and makes the temperature rise. • The further away the molecules, the less they’ll touch. • That decreases molecular friction,

and makes the temperature lower.

States of Matter• Gases have the most KE. They move

freely and randomly. • Because they have more space to move,

these molecules move with 100% translational KE. • Liquids are in between solids and gases.• Solids have the least KE. The molecules

are crammed very close together. • Solid molecules move with 100% vibrational KE.

Measuring Temperature• We measure temperature with 3

different scales• Fahrenheit• Celsius• Kelvin

Fahrenheit• ºF is the English Standard unit for

measuring temperature. • Began by filling the thermometer

with mercury.• ºF can be positive or negative.• Freezing point of water: 32ºF.• Boiling point of water: 212ºF.

Celsius• ºC is the metric unit of measuring

temperature. • Based off of thermometers filled with ethanol.• ºC can be positive or negative.• Freezing point of water: 0ºC.• Boiling point of water: 100ºC.

Kelvin• K (NEVER ºK) is the scientific unit of

measuring temperature. • K uses the same increments as celsius.• K measures the movement/energy of

the molecules.• Absolute zero- no molecular vibration.

This is 0 K. • Nothing has ever hit absolute zero.

Even the blackness of space has 2.3 K.

Examples of Temperature

Kelvin Celsius Fahrenheit

Surface of temp of Sun 5800 K 5537ºC 9,999ºF

Boiling point temp of H2O 373 K 100ºC 212ºFHuman body temp 310 K 37ºC 98.6ºFMelting point temp of H2O 273 K 0ºC 32ºFZero Fahrenheit 255 K -18ºC 0ºFAbsolute Zero 0 K -273ºC -459ºF

Conversions!• Celsius and

Fahrenheit• Celsius to Kelvin

Heat• The transfer of internal energy from

one object to another. • CANNOT be directly measured. • Indicates temperature changes.• Temperature going down? Losing

energy = loss in heat. • Temperature going up? Gaining

energy = rise/gain in heat.

Internal Energy• Internal Energy = the energy within

the molecules of the matter in the object. • Examples: •Chemical PE that could be released during reaction.•KE of individual molecules moving.

Heat and Energy Transfer• When objects interact, there are 3

types of heat transfer that can occur. • Conduction• Convection• Radiation

Conduction• Conduction – transfer of energy/heat

by touch or contact.• This energy passes through matter

because of molecule to molecule vibration.• Most affective through solid.

Radiation• Transfer of energy from light passing

through air or space.• All light has energy.• We cannot see all forms of light. We

can’t see gamma, x-ray, UV, infrared, microwave, or radiowaves.

Convection• Transfer of energy that

happens in circular columns.• Occurs in liquids and

gases. • Warm air is less dense

than cold air, and this makes the warm air rise. As it gives off energy, it becomes more dense and sinks. • Think about tornados.

Insulators• Materials that Slow or prevent

transfer of energy. • Examples!•Plastics and Rubber•Water and Air•Glass•Wood•Styrafoam

Conductors• Materials that quickly transfer

energy easily. • Examples!•Metals•Salts

Thermodynamic Equilibrium• If two or more objects are touching

and are the same temperature, the energy transfer between them is equal.

Laws of Thermodynamics• There are 4 laws of thermodynamics.• The laws explain how energy will

move. They do not explain why the energy moves.

0th Law of Thermodynamics• If two or more objects are in contact

with each other and are the same temperature, they are at thermodynamic equilibrium.

1st Law of Thermodynamics• When heat energy is added to

matter, the total heat added to the matter equals the internal energy of the matter minus the work it preformed.

2nd Law of Thermodynamics• Energy moves down the energy

gradient. So energy will move toward where there is less energy: i.e., heat energy will move toward the cold

3rd Law of Thermodynamics• Absolute zero is a real number. If

anything is found at it, it will be a crystaline solid and will have NO energy transfer.

Entropy • A measure of disorder or randomness in molecules. • The more KE something has, the more entropy it has.