Thermal Energy and Temperature Amole 2013

What is Thermal Energy? Energy is the ability to do work It is required to move or change matter in any way Thermal energy is the total kinetic energy of particles that make up a substance More kinetic energy in particles means greater thermal energy

Check your Understanding Which object in the pictures below has the most thermal energy?

What is Kinetic Theory? Kinetic Theory describes the behavior of particles in relation to thermal energy The three main points are… All matter is made up of atoms and/or molecules that act as tiny particles These particles are always in motion. Particles move faster at higher temperatures. At the same temperature, more-massive (heavier) particles will move slower than less massive (lighter) particles.

What is TEmperature? A measure of the average kinetic energy of the particles in an object Tells how hot or cold something is Thermometers are used to find this value Units for temperature are degrees… Celsius Fahrenheit Kelvin

Check your Understanding Which object in the pictures below has the greatest temperature?

How do thermometers work? Most substances expand when heated The liquid in the thermometers (usually colored alcohol or mercury) expand as the temperature increases 1. Temperature rises 2. Particles in thermometer gain energy 3. Faster particles cause them to move farther apart and up the tube

What is TEmperature? A measure of the average kinetic energy of the particles in an object Tells how hot or cold something is Thermometers are used to find this value Units for temperature are degrees… Celsius Fahrenheit Kelvin

Temperature has 3 scales Fahrenheit Used in Unites States Water freezes at 32˚F Water boils at 212˚F Celsius Used by most other countries and scientists One ˚C is 1.8 (9/5) larger than one ˚F Water freezes at 0˚C Water boils at 100˚C

Temperature has 3 scales Kelvin Used to express very cold temperatures One Kelvin is equal to the size of one °C. Based on absolute zero Absolute zero is the temperature at which all molecular motion stops (0 K)

Temperature scales

Check your Understanding A. What is the temperature of freezing water? 1) 0°F 2) 0°C 3) 0 K B. What is the temperature of boiling water? 1) 100°F 2) 32°F 3) 373 K C. What is the temperature of absolute zero? 1) 0°C 2) 32°F 3) 0 K

Temperature Conversions On the Fahrenheit scale, there are 180°F between the freezing and boiling points and on the Celsius scale, there are 100°C. 180°F = 9°F = 1.8°F 100°C 5°C 1°C In the formula for the Fahrenheit temperature, adding 32 adjusts the zero point of water from 0°C to 32°F. TF = 9/5 TC + 32 or TF = (1.8 TC ) + 32

Temperature Conversions TC is obtained by rearranging the equation for TF. TF = 1.8TC + 32 Subtract 32 from both sides. TF - 32 = 1.8TC ( +32 - 32) TF - 32 = 1.8TC Divide by 1.8 =°F - 32 = 1.8 TC 1.8 1.8 (TF - 32) = TC 1.8

Temperature Conversions The Kelvin temperature scale has 100 units between the freezing and boiling points of water. 100 K = 100°C or 1 K = 1°C is obtained by adding 273 to the Celsius temperature. TK = TC + 273

Solving A Temperature Problem A person with hypothermia has a body temperature of 34.8°C. What is that temperature in °F? TF = 1.8 TC + 32 TF = 1.8 (34.8°C) + 32° = 62.6 + 32° = 94.6°F Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Check your Understanding The normal temperature of a chickadee is 105.8°F. What is that temperature on the Celsius scale? Formulas: °F = 1.8 (°C) + 32 K = °C +273 °C = (°F – 32) °C = K -273 1.8

Solution 41.0 °C TC = (TF - 32°) 1.8 = (105.8 - 32°) = 73.8°F = 41.0°C = (105.8 - 32°) = 73.8°F = 41.0°C 1.8°

Check your Understanding On a cold winter day, the temperature is –15°C. What is that temperature in °F? Formulas: °F = 1.8 (°C) + 32 K = °C +273 °C = (°F – 32) °C = K -273 1.8

TF = 1.8 TC + 32 Solution 5°F TF = 1.8(–15°C) + 32° = – 27 + 32° = – 27 + 32° = 5°F

Check your Understanding What is normal body temperature of 37°C in Kelvins? Formulas: °F = 1.8 (°C) + 32 K = °C +273 °C = (°F – 32) °C = K -273 1.8

Solution 310. K TK = TC + 273 = 37°C + 273 = 310. K