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Activity 8 Chemical Energy. Bond Energies. A chemical reaction involves reactants and products Reactants = the substances (compounds or elements) that go into a reaction Products = the substances produced by the reaction
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Bond Energies • A chemical reaction involves reactants and products • Reactants = the substances (compounds or elements) that go into a reaction • Products = the substances produced by the reaction • Chemical reactions require the breaking of bonds in the reactants and forming of new bonds in the products.
Bond Energies • It takes energy to break a bond. • Energy is released when new bonds are formed. • This released energy used to be stored in chemical bonds.
Reactions • The minimum amount of energy needed for a chemical reaction to start is called activation energy. • Energy in reactions can be observed by a change in temperature (amount of heat).
Types of Reactions • Endothermic Reactions • Exothermic Reactions
Endothermic Reactions • The bonds of the reactants are stronger than the bonds in the products. • Energy is required for the reaction to begin. • Heat energy is absorbed.
Examples of Endothermic Reactions • The cold pack you made. • Melting • Evaporation
Exothermic Reactions • The reactants have weaker bonds than the products. • Heat is released.
Examples of Exothermic Reactions • Condensation • Burning of gasoline • Explosions
Types of Energy • Potential Energy • The amount of energy stored by an object. • Kinetic Energy • The amount of energy in motion.
Heat and Temperature • Heat is one form of energy. • Heat is caused by the transfer of energy, which will cause a change in kinetic energy. • Temperature is a measure of how hot or cold something is. • Temperature is determined by the speed of molecular movement. • The faster the molecules move, the higher the temperature.