Heat, temperature, heat transfer, 1st Law of ThermodynamicsThursday, January 28, 2015

Thursday, 1/28 Respond to the following on your weekly warm-up sheet:1. What is kinetic energy?2. What variable in the equation KE=1/2mV2 will increase the kinetic energy of an object?Upcoming dates: Wednesday, 2/3 – Thermodynamics quiz Wednesday, 2/3 – Thermodynamics project due Friday, 2/5 – Thermodynamics test and missing work deadline Tuesday, 2/16 – Electricity quiz Wednesday, 2/24 – Electricity quiz Friday, 2/26 – Electricity Test and missing work deadline Thursday, 3/3 – Magnetism quiz Friday, 3/4 – 3NWS Extra credit due by 4:00 PM Wednesday, 3/9 – Magnetism test Friday, 3/11 – End of the 3NWS

Heat, temperature, and equilibrium – 7 minutes Go to today’s resources on my webpage and

click on ‘heat and temperature notes’ Use the following questions to guide your notes.

What is heat? How does heat flow? What is temperature? What happens at when a substance reaches

equilibrium? Complete the ‘check your understanding’

questions at the end of the notes.

Review notes

Heat Transfer of energy (macroscopic level) Changes the average kinetic energy of particles

(particulate level). Energy transfers from higher temperature to

lower temperatures. An object decreases its temperature by

releasing energy in the form of heat to its surroundings.

An object increases its temperature by gaining energy in the form of heat from its surroundings.

Temperature Measures the ability of substance/physical system

to transfer energy to another substance/physical system.

Is a measure of kinetic energy of the molecules which make up a substance.

The temperature of a substance will increase/decrease if the average kinetic energy of its particles is increased/decreased.

The higher the temperature transfer heat The lower the temperature receive heat

Equilibrium point As long as there is a difference in temperature

between the system and surroundings, heat will be transferred.

When the temperature difference between the system and surroundings is zero the system and surroundings have reached equilibrium.

Check your understanding

How is heat transferred? Three methods of heat transfer

Convection Conduction Radiation

You will work in pairs and do the following: Visit the resource links to my webpage Review the documents and take personal

notes as applicable. Search the web for diagrams, pictures,

photos, videos of the three forms of heat transfer.

Complete the summary form(one per person).

Heat Transfer Summary Sheet You will have 20 minutes to complete

the summary sheet. When you have finished turn it into the

black tray.

First and Second Laws of Thermodynamics – 5 minutes Go to today’s resources on my webpage and

click on ‘Laws of Thermodynamics notes’ Use the following questions to guide your notes.

What is Internal Energy? What is the first law of thermodynamics? What is a reversible and irreversible process? What is the second law of thermodynamics?

Complete the ‘check your understanding’ questions at the end of the notes.

First Law of Thermodynamics Energy can be changed from one form to

another, but it cannot be created or destroyed. The total amount of energy and matter in the

Universe remains constant, merely changing from one form to another.

The First Law of Thermodynamics (Conservation) states that energy is always conserved, it cannot be created or destroyed. In essence, energy can be converted from one form into another.

Processes in natureTypes of processes

Reversible – is a process that after it’s finished can go backwards and end up where it started.

Irreversible – is a process that cannot go back and restore itself

All processes that occur in nature are irreversible (ex. a flower pot is dropped and shatters on the ground – the pot cannot be restored to it’s original state on its own).

Entropy Is a measure of disorder of a system

Diagram source cnx.org

Entropy Relating entropy to different states of matter

When a substance is in a gas stage there’s more disorder than there is in a liquid stage because the molecules are held closer together in a liquid form.

When a substance is in a liquid stage there’s more disorder than there is in a solid stage because the molecules are held closer together in a solid stage.

Diagram sources www2.ucdsb.on.ca and cnx.org

Restating the 2nd Law of Thermodynamics Natural processes tend to move toward a state of

greater entropy.

Cool DownDo you think all substances/objects gain and lose heat at the same rate? Explain your position.

Share your cool downDo you think all substances/objects gain and lose heat at the same rate? Tell your elbow partner your thoughts and explain your position.

What is specific heat? Every substance gains or loses heat

based on its identity/physical property.

The physical property of a substance is its specific heat capacity.

Examples of specific heat

What is specific heat capacity? Is the amount of heat (thermal energy)

required to raise a unit of mass of the substance by one degree of temperature (liquids and solids).

Measure of how much thermal energy is required to change the temperature of a substance.

What is the equation for calculating heat change

How do you determine if heat is gained or lost If heat energy is gained Q is positive.

If heat energy is lost Q is negative.

Example problem

Practice Problems