Heat

Chapter 9

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

Lesson 1 Heat SourcesThe sun is earth’s most important heat source

Heat source place from which heat comes

The other types of energy can produce heat energy

Lesson 1 cont.Examples:Rubbing your hands changes mechanical to heat

Burning fuel changes chemical to heat

A toaster changes electric to heat

ReviewIn 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 apartLiquid to gas evaporation

Solid to liquid meltingSolid to gas sublimation

Lesson 2 cont.Taking heat away: particles move less and closely packedGas to liquid condensation

Liquid to solid freezingGas to solid deposition

Lesson 2: Expansion/Contraction

Expand fill more spaceGases = mostSolids = less

Contract fill less spaceException:Water contracts until 4° then expands until 0°

Lesson 3: TemperatureTemperature measure how fast particles are moving

Faster particles = higher temp.

Thermometer device used to measure temperature

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

Celsius To Fahrenheit:(1.8 * Celsius) + 32

Celsius & KelvinCelsius To Kelvin: Celsius + 273

Kelvin To Celsius :Kelvin - 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 liquidWater’s freezing/melting points 32°F or 0°C

Lesson 3: Boiling Point

Boiling point temp. at which liquid changes to gasWater’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 HeatTemperature 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

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 HeatCalorie unit of heatCalorie the amt of heat needed to raise 1 gram of water 1°C

Heat = ∆ temp x masscalories = 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:

RadiationConductionConvection

RadiationWe get sun’s heat through radiation

Radiation movement of heat through a vacuum

Vacuum space with no matter

ConductionConduction 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