Changes in Matter

Physical Changes A physical change changes the form (shape) or appearance of matter but NOT what it is made of It is still the same substance Physical changes change physical properties and do NOT change chemical properties Examples of physical changes? Crushing, dissolving, bending, tearing Any changes of state/phase (boiling, melting, evaporating, etc.)

Chemical Changes A chemical change is a chemical reaction in which o ne or more substances (REACTANT(S)) transform into something new (PRODUCT(s))chemical reaction Atoms are rearranged The product(s) has different chemical properties from the reactant(s) You can only reverse a chemical change by doing another chemical change

Chemical Changes Examples of chemical changes? Photosynthesis, combustion, decomposition, fermentation, rusting/oxidation, cooking, tarnishing, and any other chemical reaction

Physical or Chemical Change?

Law of Conservation of Mass In a chemical change, the mass of the products ALWAYS equals the mass of the reactants This is called the Law of Conservation of Mass Matter is NEVER created or destroyed—atoms are only rearranged

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Changes in Matter & Energy What is temperature? How hot or cold something is Related to how much the particles are moving Thermal energy is the total energy of the motion of all the particles in an object Thermal energy always flows from HOT  COLD Chemical energy: energy stored in bonds between atoms What types of things have chemical energy? Food and fuel

Endothermic Changes (Or endothermic reactions) Endo = inside A chemical change in which energy is absorbed Makes surroundings cooler Examples? Instant ice pack, ice melting (ice + energy = water)

Exothermic Changes Or exothermic reactions Exo = outside A chemical change that releases energy Makes surroundings warmer Examples? Combustion Methane + oxygen = carbon dioxide + water + energy

Bellringer 10/16 What is the difference between an endothermic and an exothermic reaction?