Endothermic change Occurs when object gains energy from other sources Added energy result in less restrictive connections between atoms, molecules Types of endothermic change I.Melting II.Evaporation or boiling III.Sublimation
Exothermic change Occurs when an object loses energy to other objects or the environment Results in more restrictive connections between atoms Types of exothermic change: I.Freezing II.Condensation III.Deposition (sublimation)
Energy transfers associated with water Energy released to solidify into ice Energy absorbed to liquefy into water Energy released to condense into liquid Energy absorbed to vaporize into a gas
Making Smores Which material involved with making a smore undergoes a phase change? Endo or Exo changes?
Fire Heat 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
Which phase changes are connected with sweating?
As you sweat, energy is transferred from your body to the water/oil droplets
Sweating 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 them The transfer of that heat helps your body cool off
Example Sweating: You lose energy (exothermic) Sweat gains energy (endothermic) Energy has been transferred, not created or destroyed You feel cooler Sweat goes from liquid to gas (boiling, evaporation)
Temperature and phase change When substance gains or loses energy, either its temperature or its phase will change, but not both at the same time When adding heat to ice, temp will not rise until all ice has melted
Conservation of mass and energy In a closed environment: Mass can not be created or destroyed Energy can not be created or destroyed If some atom/molecule gains energy in some form, another must lose energy in some form
Conservation of a system The amount of mass or energy in a closed system remains constant, but can be rearranged or transformed
Closed System A closed system is a collection of objects that can transfer energy, mass only between themselves There is no gain or loss of energy, mass from a closed system
Refrigerators The refrigerant in the coils at the back of the refrigerator take out energy from air inside the refrigerator. Refrigerant evaporates inside coils Gas flows to outside of refrigerator, releases heat to environment, refrigerant condenses
Air Conditioner Hot, humid air is sucked in from the room Heat is extracted from air and transferred to water in piping The cool dry air is recycled back into room Water condenses inside the air conditioner A fan takes the heat from the water and blows it away from unit outside of home