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 Chemical Reaction- When substances change chemically to form a new substance. 1. Forms new bonds between atoms. 2. Make new substances 3. Example- 2 hydrogen atoms (gas) +1 oxygen atom (gas) react to form 1 water molecule (h20)  What happens in a reaction? 1. Reactants react to create a product. Reactants- the materials that exist before the chemical reaction Products- Substances that are created by the chemical reaction 2. In a reaction atoms are arranged and no new atoms are created.  Electrons are the atoms that are effected by the chemical reaction.  Law of Conservation of mass is a relation saying that during the reaction the mass is neither created or destroyed.

4. The temperature of the chemical changes from before. 2. The chemical changes color. 1. A gas is produced 3. Chemical starts to bubble. How do you know a reaction occurred? All pictures from ps/chm/100/dgodambe/thedisk/chemrxn/signs4.ht m

 Energy is needed to break chemical bonds so they can start a chemical reaction. Energy is released when bonds form.  Chemical Energy- energy that is stored in atoms and molecules. Chemical energy can be released during a reaction.  Endothermic- Photosynthesis is an example of an endothermic reaction. Plants use the energy to form the sun to convert carbon dioxide and water into the glucose and oxygen.  Exothermic- Mixture of sodium and chlorine to yield table salt. This reaction produces 411 (kj) of energy for each mole of salt that is produced. Potential Energy is stored energy of position of an object. Activation Energy is usually when the chemical reaction result as a collusion between reacting particles. Image1: ss/energy/u5l1b.html Image2: sc/en/ch/12/oc/substitution/sn_2/aktivierungsenergie_s n2/tempkurven.gif

Exothermic processes Making ice cubes Formation of snow in clouds Condensation of rain from water vapor A candle flame Mixing sodium sulfite and bleach Rusting iron Burning sugar Forming ion pairs Combining atoms to make a gas phase Mixing water and strong acids Mixing water with an anhydrous salt Crystallizing liquid salts Nuclear fission Mixing water with calcium chloride Endothermic processes Melting ice cubes Conversion of frost to water vapor Evaporation of water Forming a cation from an atom in the gas phase Baking bread Cooking an egg Producing sugar by photosynthesis Separating ion pairs Splitting a gas molecule apart Mixing water and ammonium nitrate Making an anrous salt from a hydrate Melting solid salts Reaction of barium hydroxide crystals with dry ammonium chloride Reaction of thionyl chloride (SOCl2) with cobalt(II) sulfate heptahydrate Exothermic Reactions- Reactions that releases energy and the temperature gets hotter. Endothermic Reactions- Reactions that absorbs energy and the temperature gets colder. This graph is showing the differences between exothermic & endothermic processes. These experiments above can be tested. An exothermic reaction watch how the temperature of the process increases and during endothermic watch how the temperature drops. citycollegiat e.com/chap ter2a.htm

Synthesis Reaction- a combo of two substances and a compound result. Decomposition Reaction- when a compound is broken down into a easier substance. Single Replacement-A metal replaces a metal or a non-metal replaces a non- metal. Double Replacement- a metal always replaces a metal & a non-metal always replaces a non-metal. Combustion Reaction- always includes oxygen. Anytime it burns it is a combustion reaction.