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Chemical Reactions

Chemical Reactions . Chemical Reaction. The process by which a chemical change occurs Atoms are rearranged, and chemical bonds are broken and reformed One or more substances change to produce one or more different substances Types Synthesis (creating) Decomposition (separating)

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Chemical Reactions

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  1. Chemical Reactions

  2. Chemical Reaction • The process by which a chemical change occurs • Atoms are rearranged, and chemical bonds are broken and reformed • One or more substances change to produce one or more different substances • Types • Synthesis (creating) • Decomposition (separating) • Combustion (burning) • Displacement/Replacement (switching) What does H2 & O2 gas create? Out of the four types of reactions, which would describe the chemical reaction taking place to the right? H2 O2

  3. Physical Change • a change in shape, size, color, or state • a change without a change in chemical composition • a change that is reversible • The Mixtures Lab Examples tearing paper cutting your hair change in state Physical changes are not indicative of a chemical reaction

  4. Chemical Change • a change in which a substance becomes another substance having different properties • a change that is not reversible using ordinary physical means • Changes that usually cause, heat, sound, light, odor, fizzing/foaming, color changes You usually need more than one of the above characteristics to be considered a chemical change! Examples mixing vinegar & baking soda burning a piece of wood soured milk A chemical analysis is the only 100% way to know a chemical change has occurred.

  5. Exothermic Reaction A chemical reaction in which energy is released. The products have greater bond energy than the reactants C6H12O6 + 6O2 6CO2 + 6H2O + energy (respiration) Endothermic Reaction A chemical reaction in which energy is absorbed. The products have lower bond energies than the reactants CO2 + H2O + energy  C6H12O6 + O2 (photosynthesis) Energy and Chemical Reactions Chemistry Comes Alive! Sample Movies TeacherTube - Videos Chemistry Demonstration Videos Can you think of other reactions where energy is gained or released?

  6. Rates of Chemical Reactions The rates at which chemical reactions can take place are based on the interaction (collisions) between the different particles. These rates can be impacted by the following: • Temperature –a measure of the average kinetic energy of the particles in a sample of matter • Ex. Increasing the temperature when cooking • Surface area – amount of material that comes into contact with the reactants • Ex. Cutting a potato into smaller pieces when cooking • Concentration – amount of substance per volume • Ex. Turning the valve on a gas stove to increase the concentration of methane molecules • Catalysts (enzymes) – organic substances that help speed up chemical reactions, but are not consumed in the reaction

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