Chapter 16: Temperature and Heat

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# Chapter 16: Temperature and Heat - PowerPoint PPT Presentation

Chapter 16: Temperature and Heat. Thermal energy that flows from something of high temp. to something of low temp. . Heat. Warm  Cold. Metric unit  Joules. Transfer of Thermal Energy. Temperature. Measure of how hot or cold an object is compared to a reference point.

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### Chapter 16: Temperature and Heat

Thermal energy that flows from something of high temp. to something of low temp.

Heat

• Warm  Cold
• Metric unit  Joules
• Transfer of Thermal Energy.

Temperature

• Measure of how hot or cold an object is compared to a reference point.
• Related to the kinetic energy in an object.
• The faster the particles move the higher the temperature.

Temperature

• The reference point on the Kelvin scale for temperature is absolute zero.
• Absolute zero – a temperature of 0°K.

Thermal Energy

• Total Potential and Kinetic Energy of an object.
• Depends on an objects mass, temperature, and phase.

Thermal Energy vs. Temperature

• Thermal energy is greater with an object with a greater mass.
• Temperature is greater with an object whose particles are moving faster.

Thermal Expansion

• Increase in an object’s volume because of an increase in temp.
• It occurs because particles tend to move farther apart as temp. increases. Example: Balloon
• Gas expands more than liquids and solids

Specific Heat

• Heat needed to raise the temp. of a 1g of an object 1o Celcius.
• Unique to every material
• The lower an object’s specific heat, the more the temp. increases when heat is absorbed.

Water has a large specific heat.

• Needs a lot of heat to change its temp

Heat is measured in Joules or calories.

• One calorie is the energy the required to raise the temp. of 1g of water by 1C.
• One calorie is equal to 1.184 J
• The unit for specific heat is J/g C

Q = m c ΔT

Heat mass specific change heat in temp.

Measuring Heat Changes

• A calorimeter is an instrument used to measure changes in thermal energy.
• It uses the principle that heat flows from hotter to colder objects until both reach the same temperature.

Conduction

• Transfer of heat through direct contact.
• Conduction in gases is slower than in liquids and solids.

or

Thermal Conductors

• Material that conducts thermal energy well.
• Examples: copper & aluminum pots & pans; wood vs. tile flooring

Thermal Insulators

• Material that conducts thermal energy poorly.
• Examples: air in a double pane window, wood, fiberglass, fat

Convection

• Transfer of heat through moving particles in fluids (liquids & gases).
• Convection Current occurs when a fluid circulates in a loop as it heats and cools. Example: oven

• Transfer of heat by electromagnetic waves

Examples: Heat from the sun, heat lamps used in restaurants

• light colored object 

Reflect heat

• dark colored object 

Absorb heat

Thermodynamics

• The study of conversions between thermal energy and other forms of energy.
• 3 Laws of Thermodynamics

1st Law of Thermodynamics

• “Energy is conserved.”
• Energy is never created or destroyed, and throughout a conversion all of the energy can be accounted for.

2nd Law of Thermodynamics

“Thermal energy can flow from colder objects to hotter objects only if work is done.”

A heat engine is any device that converts heat into work.

Thermal energy that is not converted into work is called waste heat.

Waste heat is lost to the environment.

3rd Law of Thermodynamics

• “Absolute zero cannot be reached.”
• Scientist have cooled matter almost to 0K, but have not been able to cool it completely.

### From his observations of cannon drilling, Count Rumford concluded that heat could NOT be a form of MATTER

1.Unit for temperature?2.Define heat3.What property of an object is related to the average kinetic energy of the particles of that object?4. As the temp of an object rises so does the _______________.5. Which device is based on the property of thermal expansion?6. Thermal energy depends on an objects ___________.

7. Know what each part of the equation represents.8. What does a calorimeter directly measure?9. Energy from the sun reaches the Earth by __________.10. Matter is needed to transfer thermal energy by _____________.11. Know a good conductor from a list of items.12. 1st law of thermodynamics says the amount of work done by a heat engine equals the amount of __________.13. Which law states that absoulute 0 can’t be reached.14. What is a consequence of the 3rd law of thermodynamics?(read from the book)15. What happens in a steam engine? (read)16. What is a fluid that vaporizes and condenses inside the tubing of a heat pump called?(read) 2 questions about heat pumps on the test!There will be fill in the blank questions with the following word bank:

Word bankconductor, compressor, phase, specific heat, from, thermodynamics, degrees Celcius, zero, vacuum, waste heat, convection, radiation, conduction, less, greater, equal, temperature, thermal expansion to, Kelvins, 1st law, 2nd law, 3rd lawProblem on specific heat