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Thermochemistry
| Term | Definition |
|---|---|
| Thermochemsitry | the study of heat changes that occur during chemical reactions and phase changes (physical changes of state) |
| Exothermic process | heat flows from the system to the surroundings, feels hot |
| Endothermic process | heat flows from the surroundings to the system, feels cold |
| Collision Theory | atoms, ions, and molecules can react to form produces when they collide, provided that the particles have enough kinetic energy |
| Activation energy | the minimum amount of energy that particles must have in order to react |
| Activated Complex | name for the arrangement of atoms at the peak of the activation energy barrier, in-between state, neither reactants nor products |
| Endothermic Reaction | reactants have less potential energy than products (reactants lower on diagram than products) Energy absorbed > Energy released |
| Exothermic Reaction | reactants have more potential energy than products (reactants higher on diagram than products) Energy released > Energy absorbed |
| calorie | commonly used unit for heat energy |
| Calorie | energy contained in the food we eat, measured in kilocalories |
| Joule (J) | SI unit for heat energy, will primarily be used for our calculations |
| calorie to Calorie conversion factor | 1000 calories = 1 Calorie =1 kilocalorie |
| Joule to calorie conversion, joule to kilojoule conversion | 4.18 J = 1 cal 1000 J = 1 kJ |
| Enthalpy (H) | represents the heat content of the material |
| change in enthalpy (ΔH) | difference in heat content between the products and reactants of a chemical reaction, referred to as heat of reaction |
| ΔH equation | ΔH=products - reactants |
| Heat flow out of the system | Hproducts – Hreactants < 0; negative ΔH, exothermic reaction |
| Heat flows into the system | Hproducts – Hreactants > 0; positive ΔH, endothermic reaction |
| energy located on products side of the reaction | Exothermic reaction, energy is released |
| energy located on reactants side of the reaction | Endothermic reaction, energy is absorbed |
| specific heat capacity (C) | amount of heat it takes to raise the temperature of 1 gram of the substance 1°C , also referred to as just specific heat |
| specific heat equation | q=mCΔT |
| units for specific heat | j/(g°C) or cal/(g°C) |
| calorimetry | way to measure the heat that is released during chemical reactions |
| Law of Conservation of Energy | energy cannot be created or destroyed, only converted into different forms |
| Calorimetry experiments | Heat released by a system = heat absorbed by its surroundings mCΔT=-mCΔT |
| calorimeter | device used to measure the absorption or release of heat in chemical and physical processes |
| bomb calorimeter | used to determine heat released during a chemical reaction or heat contained in the foods we eat |
| melting | solid to liquid, endothermic |
| freezing | liquid to solid, exothermic |
| vaporization | liquid to gas, endothemric |
| condensing | gas to liquid, exothermic |
| sublimation | solid to gas (without passing through liquid phase), endothermic |
| deposition | gas to solid (without passing through liquid phase), exothermic |
| two types of vaporizaton | evaporation and boiling |
| evaporation | vaporization only at the surface, occurs at temperatures below the boiling point |
| boiling | vaporization throughout the liquid, bubbles are bubbles of vapor forming and when pressure inside equals atmospheric pressure vapor is released |
| normal boiling point | boiling point at a pressure of 1 atmosphere |
| changes in boiling point based on external pressure | higher external pressure=higher boiling point lower external pressure=lower boiling point |
Created by:
msbaker
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