# Heat - PowerPoint PPT Presentation

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Heat. The motion of the particles of matter. Heat Transfer. Heat flows from an area of high heat to an area low in heat. Three methods of heat transfer. Conduction: Transfer from one substance to another by direct contact of molecules. Example: When you touch a hot stove. Convection:

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Heat

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## Heat

The motion of the particles of matter

### Heat Transfer

• Heat flows from an area of high heat to an area low in heat.

### Three methods of heat transfer

Conduction:

• Transfer from one substance to another by direct contact of molecules. Example: When you touch a hot stove.

• Convection:

• Heat carried from one place to another in a liquid or gas as molecules move in currents caused by density differences. Example: Warm air rising.

• Heat carried through empty space in the form of infrared rays. Example: When you face the sun and feel warmth on your face.

• ### Temperature:

• A measure of the average kinetic energy of molecules.

• The faster the molecules of a substance are moving, on average, the higher the temperature.

• Thermometer - An instrument for measuring temperature.

### How do you set a temperature scale? (watch the videos below!)

• How Fahrenheit made his Temperature scale-

• The Celsius Scale

• Fahrenheit based it on his own body temperature (100°F) and the freezing point of saturated salt water.

• Celsius based it on the boiling point of water (100°C) and the freezing point of water.

• Kelvin has the same degree scale as Celcius, but starts at absolute zero.—no negative temperatures!

### Temperature Scales:

• Celsius -

• Most common scale world wide - Used in all scientific measurements.

• Freezing point of water is 0o C.

• Boiling point of water is 100o C.

• Kelvin -

• An "absolute" scale used for kinetic theory calculations.

• Zero on this scale, 0 K, is the lowest possible temperature.

• Note the way the temperature is written, 0 K. This is read as "zero kelvins", without using the word degrees.

• To convert Celsius degrees to kelvins, add 273 to the Celsius temperature.

• Fahrenheit -

• The temperature scale generally used in the United States.

• Freezing point of water is 32 oF.

• Boiling point of water is 212 oF.

• While converting between oC and oF is not stressed in this class, a "ball park" conversion would be oC = (oF - 30) / 2. While this gives a Celsius temperature that is a little low, it is a quick way to compare the two scales.

### Absolute Zero

• - The lowest possible temperature.

• The temperature would be 0 K or about -273 oC.

### Calorie:

• The unit of heat.

• The amount of heat needed to raise the temperature of one gram of water one degree Celsius.

• A "Food Calorie" is 1000 calories, or a Kilocalorie

### Specific Heat

• The ability of a substance to absorb heat.

• Number of calories needed to raise the temperature of one gram of the substance one Celsius degree.

• The units of Specific Heat are - calories per gram Celsius degree.

### EQUATION

Q = cm DT

DT = final T – initial T

• Heat gain/lost =(mass) (change in Temp) (spec. heat)

• Specific heat of water

c = 1 calorie/gram°C