Heat and Temperature

Temperature Objective  Define temperature in terms of the average kinetic energy of atoms or molecules  Convert temperature readings between the Fahrenheit, Celsius, and Kelvin  Describe heat as a form of energy transfer

Temperature and Energy All particles in a substance are moving  Particles have kinetic energy  Temperature is the measurement of average kinetic energy  More kinetic energy the higher the temperature

Thermometers Use a simple physical property  Most objects expand when their temperature rises  Ordinary thermometers will use mercury or colored alcohol which expand and contract as temperature changes Caused by exchange of energy from thermometer and surroundings –Why not water?

Thermometer variations Dial thermometers with pointers  Use 2 types of metals for coil to control arrow – coil unwinds lowering pointer Digital thermometer  Measures temperature by change in current  Change in temperature changes electric current-it all has to do with kinetic energy

Fahrenheit, Celsius and Kelvin Fahrenheit Scale  Used in U.S. but no place else  Unit of measure is degrees- o F  Water freezes at 32 o F  Water boils 212 o F

Celsius (centigrade)  Used in most countries and in science  Water freezes at 0 0 C  Water boils at C  Difference between freezing and boiling is divided in 100 equal parts called degrees Celsius- 0 C  Degree of Celsius is 2x the degree of Fahrenheit

More Equations: Celsius-Fahrenheit Conversion Equation Fahrenheit temp=(9/5 x Celsius temp) T f = 9/5t Fahrenheit-Celsius Conversion Equation Celsius Temp = 5/9(Fahrenheit temp -32.0) t= 5/9 (T f )

Kelvin Scale  Based on absolute zero The point where the energy of an object cannot be any lower Equal to C Lowest point on Kelvin Scale is 0K No negative numbers  Another equation (it easy)-Celsius to Kelvin Kelvin temp = Celsius temp T= t + 273

Math Skills page 328 Practice questions Page 328 page 1-4

Relating Temperature to Energy Transfer as Heat Why does ice melt in your hand?  Ice has lower temperature than your hand  Molecules in ice are moving slower than molecules in hand  Energy transferred from fast moving molecules of hand to slower ice molecules  Ice molecules speed up which increases kinetic energy – causes ice to melt

The transfer of energy between the particles of 2 objects due to temperature difference between the 2 objects is called The transfer of energy goes from hotter to colder What happens if you hold a hot water bottle? What happens when drinks are put into ice? What happens when you put your hands together?

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