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Chapter 10 Heat and Heat Technology Word Ball & Ring Set Demonstration (PS 7) Name ____________________________ Explanation What happened when ball was heated? The ball wouldn't fit through the ring - the ball got larger/metal expanded Drawings/Examples What happened when the ball was placed in water? The water vaporized to steam/energy from the metal transferred quickly to the water (high to low temp) so the ball contracted and fit back through the ring Temperature (BrainPop) The measure of the AVERAGE ___kinetic energy___ of the particles/molecules in an object. (not all particles moved at the same speed) NOT affected by amount: Temp _is not__ determined by how much of a substance you have so a pot of tea __will___ have the same temperature as a cup of tea poured from the pot even though there is more tea in the pot. Same temp when you first pour! More energy = higher temp! Kinetic Energy of Particles The __movement___ of the object's particles the __faster___ the particles are moving, the _more___ kinetic energy they have. Temperature: Used in Science: Celsius & Kelvin (SI) 100 ºC Celsius Celsius - Unit__ºC__ Boiling Point__100 ºC __ Freezing Point __0 ºC ___ Room Temp ___20 ºC ___ Kelvin - Unit _K__ (no degree sign/ no negative numbers) Boiling Point ___373 K__ Freezing Point __273 K__ Room Temp _293 K__ 373 K Kelvin 0ºC 273 K Zero Kelvin = 0 K Absolute Zero The _lowest_ point on the Kelvin scale when all molecular motion ceases/stops. Thermal Expansion Heat The increase in _ volume_ of a substance due to an __increased___ change in temperature because the molecules move __faster__ and __spread apart__, taking up more space ( ___volume__ ). The particles themselves don't expand... they spread out causing the whole object to expand and take up more space (less attraction between the particles) Ex: bridge joins and alcohol in thermometers (expands when higher temp) Most substances _contract_ when cooled and energy is __released_. The temperature _decreases_ as the average kinetic energy __decreases_. Unit __Calories / (C) or Joules (J)__ The _TRANSFER_ of energy between objects that are at different _temperatures__ (BrainPop) Transfer enough energy & you get a change of state – physical change! Temperature vs Temperature is a measure of the average amount of __Kinetic Energy__ and heat is the __transfer_ of energy due to a difference in temperature. Heat Thermal Energy (TE) Relationship between Heat and Thermal Energy Pick up a wooden vs a metal spoon. Why does the metal spoon "feel cold" and the wooden spoon does not? (hint: think about insulators & conductors) you are transferring energy from your hand to the metal spoon but not so much energy from your hand to the wooden spoon Insulators don’t transfer energy Low or high amounts of TE? The __TOTAL_ amount of energy of __all__ the particles in a substance. Unit: __Joules (J)___ High temp = _more_ thermal energy Low temp = _less__ thermal energy Why? the higher temp is due to the particles moving faster and therefore more movement = more TE More particles = __more__ thermal energy More particle movement = _more__ thermal energy. True or False: A cup of hot coffee has the same amount of thermal energy as a cup of iced coffee. Does thermal energy depend partly on temperature? Yes, because the amount of movement determines the amount of TE Which has more Thermal Energy - pot or cup of same temp. tea? Pot because it has more particles... but the temperature would be the same Energy is always transferred from the object with the ____higher______temperature to the object with the ___lower_______ temperature until both objects reach the ___same___ temperature. This will continue until both objects reach the same temperature and is called _____thermal equilibrium___. One object may have more thermal energy because there is more of it, but both objects would have the same temperature. So, why does the ice melt in a cooler when you add cans or bottles of drinks that are at room temperature? Because the energy from the higher temp drinks is transferred to the lower temp ice until the temperature of everything is equal Word *Conduction (Energy Transfer) Explanation The __transfer___ of thermal energy through ____direct contact___ - requires matter. Drawings/Examples Touch the metal spoon that has been sitting in the boiling soup on the stove. Why did the spoon get hot? Because the transfer of energy from the soup to the spoon and then transferred to your hand when you touched the spoon. Substances that transfer thermal energy well Example: Metals Substances that do not transfer thermal energy well (may slow the transfer or reduce the amount of transfer) The __transfer__ of thermal energy by movement of __liquids_ or __gasses__. (called “fluids” in the CE Lab) Examples: Glass, rubber, plastic, wood, insulation, paper, fabrics Drop food coloring into different temps of water. What happened in the Low Temp Particles not moving quickly so spread slowly Higher Temp - Particles moving quickly so spread quickly...warmer water rises & cooler water sinks Examples: heat/cooling our homes (where are our vents?), warming a swimming pool, convection oven Conductor Insulator *Convection (Energy Transfer) Convection flow & density... Denser air/liquid (cooler/lower temp contracts) _sinks__ and pushes the less dense (warmer/higher temp - expands) air/liquid _up_ *Radiation (Energy Transfer) Examples: campfire or sun The __transfer_ of thermal energy through Or the waves of energy radiating __matter___or ___space__ as electromagnetic off of the asphalt on a hot day __waves__. No matter needed! Greenhouse Effect Thermal Conductivity - the rate at which substances conduct thermal energy Heat & Temperature Change Which will reach a higher temperature faster? Why? metals are good conductors Silver coins or water Cooper pan on a stove or its wooden handle Unit: _______________ The amount of energy needed to change the Specific Heat __temperature___ of 1 kg of a substance by Capacity 1 ºC Water 4284 J/kgºC / Sand 830 J/kgºC (Why coastal areas Low Specific Heat (gain/lose energy easily) stay warmer longer gain a little energy & temp increases quickly than inland areas) Example: metals (conductors!) – water has a High Specific Heat (gain/lose energy slowly)higher specific need to gain a lot of energy in order to heat capacity increase temp compared to land Example: water – used in LOTS of systems to remove excess TE – cars/home As thermal energy is added to or taken away Phase Change & from a system, the temperature does not Temperature always change! There is no change in temperature during a __phase change____ because the energy is being used to make or break bonds between molecules, but not change the temperature. Change in amount of energy! Air is heated by a furnace and the fan Heat Pump forces/pumps the heated/high temp air (Heat Technology) through a system of ducts to the vents in each room. The cooler/low temp air returns through the "intake" where you put your air filters. (convection currents) Thermostat Uses __thermal expansion__ of metal inside (Heat Technology) to turn on/off the AC or heat Refrigerator (Heat Technology) ___Removes__ the higher temp air using a coolant that removes the thermal energy Heat Engine (Heat Technology) Devices that convert __thermal__ energy into __mechanical__ energy. Geothermal Systems (Heat Technology) Thermal Pollution Changes the thermal energy in the ground (temp around 50ºF) into useful energy for homes/buildings The excessive heating of a body of ____water___ by power plants or industrial plants Why is the metal buckle of a seat belt at a much higher temperature than the cloth seat belt in a car on a hot/high temp day? metal has low specific heat capacity and gets hotter quicker with just a little bit of heat whereas the cloth has a higher specific heat capacity and it takes a lot of energy to raise its temperature Heat Transfer Investigation TWO Freezing/melting occur at same temp! Condensation and vaporization occur at same temp! Pg 264 Also used for AC system – removes thermal energy Pg 250 - bimetallic strip expands/contracts to open/close circuit Pg 268 Pg 266 Internal combustion engine - ex: car or lawn mower engine External combustion engine ex: rocket Ex: hot water heaters, heat pumps, geothermal power plants Pg 269 Ex: water used to cool machines, now at higher temp, is dumped into ponds/lakes