Chapter 9 Heat

Heat form of energy from the motion of particles Lesson 1: What is Heat? Heat form of energy from the motion of particles Heat always flows from warmer to cooler Machines change heat energy into mechanical energy

The sun is earth’s most important heat source Lesson 1 Heat Sources The sun is earth’s most important heat source Heat source place from which heat comes The other types of energy can produce heat energy

Examples: Rubbing your hands changes mechanical to heat Lesson 1 cont. Examples: Rubbing your hands changes mechanical to heat Burning fuel changes chemical to heat A toaster changes electric to heat

Review In a solid particles are closely packed and move little In a liquid particles are slightly farther apart and move a little more In a gas particles can move anywhere in the space

Lesson 2: Heat Affects Matter Adding heat: particles move faster and farther apart Liquid to gas evaporation Solid to liquid melting Solid to gas sublimation

Taking heat away: particles move less and closely packed Lesson 2 cont. Taking heat away: particles move less and closely packed Gas to liquid condensation Liquid to solid freezing Gas to solid deposition

Lesson 2: Expansion/Contraction Expand fill more space Gases = most Solids = less Contract fill less space Exception: Water contracts until 4° then expands until 0°

Temperature measure how fast particles are moving Lesson 3: Temperature Temperature measure how fast particles are moving Faster particles = higher temp. Thermometer device used to measure temperature

Fahrenheit To Celsius: 5/9 * (Fahrenheit - 32) Fahrenheit & Celsius Fahrenheit To Celsius: 5/9 * (Fahrenheit - 32) Celsius To Fahrenheit: (1.8 * Celsius) + 32

Celsius To Kelvin: Celsius + 273 Celsius & Kelvin Celsius To Kelvin: Celsius + 273 Kelvin To Celsius : Kelvin - 273

Fahrenheit To Kelvin: (5/9 * (Fahrenheit - 32) + 273 ) Fahrenheit & Kelvin Fahrenheit To Kelvin: (5/9 * (Fahrenheit - 32) + 273 ) Kelvin To Fahrenheit: ((Kelvin - 273) * 1.8 ) + 32

Lesson 3: Freezing Point/Melting Point Freezing point temperature at which liquid changes to solid Melting Point temp. at which solid changes to liquid Water’s freezing/melting points 32°F or 0°C

Boiling point temp. at which liquid changes to gas Lesson 3: Boiling Point Boiling point temp. at which liquid changes to gas Water’s boiling point is 212°F or 100°C

Lesson 3: changing freezing/boiling point To change the freezing pt. of H2O add antifreeze (it has alcohol) Compounds of Na & Ca are used on icy roads to keep H2O from freezing

Lesson 4: Measuring Heat Temperature avg. kinetic energy Heat total kinetic energy Heat depends on temp. & amount of matter (mass)

Lesson 4: heat vs. temp. 2 objects same temp. but different masses  the 1 w/ more mass = more heat 2 objects diff temp & diff mass  the 1 w/ more mass = more heat even if temp

A candle flame and a bonfire  bonfire has more heat Lesson 4 cont. A candle flame and a bonfire  bonfire has more heat An cup of hot cocoa and a frozen pond  frozen pond has more heat because it has more mass even though it is colder

Lesson 4: Measuring Heat Calorie unit of heat Calorie the amt of heat needed to raise 1 gram of water 1°C Heat = ∆ temp x mass calories = mass H2O × ΔH2O temp. × 1.0 cal /g/°C

Simple Calorimeters

Lesson 4: endothermic vs. exothermic Endothermic absorbing heat leaving the surroundings cooler Endothermic requires kinetic energy

Exothermic giving off heat leaving the surroundings warmer Exothermic kinetic energy is released

Lesson 5: How Does Heat Travel? Energy always goes from warmer to cooler There are 3 ways heat can travel: Radiation Conduction Convection

We get sun’s heat through radiation Radiation movement of heat through a vacuum Vacuum space with no matter

Conduction movement of heat from one molecule to another Conductor heat travels through easily Insulator does not conduct heat easily

Convection Convection movement of heat where warm liquids or gases rise and cool liquids or gases sink

Dark colors absorb heat Light colors reflect heat