2 Section 1: Temperature, Thermal Energy, and Heat
3 TemperatureA measure of the average kinetic energy of the individual particles in matter.The faster the particles move, the more kinetic energy.We use a thermometer to measure temperature.3 Scales: Celsius, Fahrenheit, Kelvin
4 Celsius scaleBoiling point of water = 100˚CFreezing point of water = 0˚CFahrenheit scaleBoiling point of water = 212˚FFreezing point of water = 32˚FKelvin scaleBoiling point of water = 373KFreezing point of water = 273K
5 ˚C = K - 273K = C formulasConvert 303K to ˚C303K – 273 = 30˚CConvert 70˚C to K 70˚C = 343Kabsolute zero = 0K or -273 ˚ CAt absolute zero, there is no kinetic energy in the particles / no thermal energy can be removed
6 Thermal Energy and Heat Thermal Energy depends upon:1. the number of particles in the object2. the temperature of the object3. the arrangement of the particlesHeat is:thermal energy which moves from a warmer object to a less warm object.Example-ice cube melting in your hand
7 Examine the beakers below. Which beaker holds more water molecules?Which beaker has a higher temperature?Which beaker has more kinetic energy?Which beaker has more thermal energy?Which beaker has the greatest mass?
8 Specific HeatThe amount of energy required to raise the temperature of one kilogram of a material by one Kelvin.Unit for specific heat: J/(kg*K) Formula:change in energy = mass x specific heat x change in temperatureMaterial with a high specific heat can absorb a lot of thermal energy without a great change in temperature.
9 Materials with a low specific heat will absorb heat quickly and easily. Ex: Sand on the beachEx: gold (bracelet)Ex: concrete/pavement/tarEx: ironEx: copperEx: silver
10 Sample ProblemHow much heat energy is required to raise the temperature of 5kg of water by 10 Kelvins?Given information:mass = 5kgchange in temp (∆T) = 10Kspecific heat of water = 4180J/(kg*K)Unknown: change in energy
11 3 Steps to Solve This Problem Formula:change in energy = mass x specific heat x ∆TSubstitution:energy = 5kg x 4180J/(kg*K) x 10KAnswer:20,900 J
13 How is Heat Transferred? 3 ways that heat can move:1. Conduction2. Convection3. Radiation
14 Conduction Heat is transferred by the direct contact of particles Example: the heat energy from the hot soup is transferred by conduction to the spoon—the spoon then becomes warm.
15 ConvectionHeat is transferred by the movement of currents within a fluid (liquid or a gas)Example: boiling water—water is moved by the currents in the fluidWhen fluids are heated, the particles move faster and further apart.Pizza ovenOpening an oven and feeling a blast of hot air
16 When fluids are heated, they rise upward because they become less dense Example: hot water/air rises and cool water/air sinksThe rise and fall of these fluids create convection currents (circular motion)
17 Radiation The transfer of heat energy by electromagnetic waves Example: fire, sun’s energyDoes not require matter to transfer thermal energy
18 Heat Moves One WayHeat will always flow from a warmer object to a cooler object.As thermal energy increases, the temperature of matter absorbing the heat increases.The temperature of the matter losing the thermal energy is dropping.Note: there is no such thing as “coldness”
19 Conductors and Insulators Conductor: material that transfers thermal energy wellmetal spoonmost metalsInsulator: material that does not transfer thermal energy wellwoodwoolstrawgoose feathers/down comforterinsulation
21 States of MatterSolidParticles are packed tightly togetherParticles only vibrateRetain their shape and volume
22 Liquidparticles are close togetherparticles are free to move arounddoes not have a definite shapehas a definite volume
23 Gasparticles are moving very fast!particles are spread very far apartgases expand to fill available spacelack a fixed shape and volume
24 Changes of StateChange of State: physical change of matter from one state of matter to another (occurs when heat energy is absorbed or released)Solid-Liquid Changes:1. melting: solid changes to a liquid2. freezing: liquid changes to a solid
25 Liquid-Gas Changes:Vaporization: change from a liquid to a gas (absorbs heat energy)1. evaporation: vaporization that takes place at the surface of a liquid2. boiling: vaporization that takes place below the surface of a liquid3. condensation: a change from a gas to a liquid (cold drink in the summer-loses heat energy)
27 Thermal ExpansionAs the thermal energy of matter increases, its particles spread out and the substance expands.The expansion of matter when it is heated is thermal expansion.Example: metal grooves on a bridge