Heat

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Heat - PowerPoint PPT Presentation

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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PowerPoint Slideshow about ' Heat ' - tatyana-valdez

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Presentation Transcript

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 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