7Endothermic change Occurs when object gains energy from other sources Added energy result in less restrictive connections between atoms, moleculesTypes of endothermic changeMeltingEvaporation or boilingSublimation
8Exothermic changeOccurs when an object loses energy to other objects or the environmentResults in more restrictive connections between atomsTypes of exothermic change:FreezingCondensationDeposition (sublimation)
9Energy transfers associated with water Energy released to solidify into iceEnergy absorbed to liquefy into waterEnergy released to condense into liquidEnergy absorbed to vaporize into a gas
10Making SmoresWhich material involved with making a smore undergoes a phase change?Endo or Exo changes?
11FireHeat from an outside source must be applied to the combustable material to make it burn (endothermic action)The products(hot air, ash) released from the chemical reaction have an increased amount of heat (endo)These products lose their heat as the move away from the source of the reaction (exothermic)The surrounding environment (air, the ring of rocks that border the fire, the marshmallow, you) become hotter as energy is transferred to you from the products of the fire
34Which phase changes are connected with sweating?
35As you sweat, energy is transferred from your body to the water/oil droplets
36Sweating Exercising increases the energy in your body Some of that energy is transferred to the molecules of water and oil that make up your sweat.Those water/oil molecule move through pores, evaporate when no longer confined inside the body, taking heat with themThe transfer of that heat helps your body cool off
37Example Sweating: You lose energy (exothermic) Sweat gains energy (endothermic)Energy has been transferred, not created or destroyedYou feel coolerSweat goes from liquid to gas (boiling, evaporation)
38Temperature and phase change When substance gains or loses energy, either its temperature or its phase will change, but not both at the same timeWhen adding heat to ice, temp will not rise until all ice has melted
39Conservation of mass and energy In a closed environment:Mass can not be created or destroyedEnergy can not be created or destroyedIf some atom/molecule gains energy in some form, another must lose energy in some form
40Conservation of a system The amount of mass or energy in a closed system remains constant, but can be rearranged or transformed
41Closed SystemA closed system is a collection of objects that can transfer energy, mass only between themselvesThere is no gain or loss of energy, mass from a closed system
43RefrigeratorsThe refrigerant in the coils at the back of the refrigerator take out energy from air inside the refrigerator Refrigerant evaporates inside coilsGas flows to outside of refrigerator, releases heat to environment, refrigerant condenses
46Air Conditioner Hot, humid air is sucked in from the room Heat is extracted from air and transferred to water in pipingThe cool dry air is recycled back into roomWater condenses inside the air conditionerA fan takes the heat from the water and blows it away from unit outside of home