Changes in Matter

Physical and Chemical Changes Physical changes are changes in which no new substance is formed Solid to Liquid (ice to water) Liquid to Gas (water to water vapor) Gas to Liquid (water vapor to rain) Liquid to Solid (water to ice) Changes in state, volume, and density are physical changes Chemical changes are changes in which a new substance is formed Electrical current in water (oxygen & hydrogen) Fuel in the space shuttle (liquid oxygen & hydrogen are burned and result in water)

Physical and Chemical Changes Burning is a type of chemical reaction Reactant = starting substances Product = new substance Reactivity = the ability of a substance to react chemically. Some are more likely to react than others Chemical reactions can be identified by: Change in color or production of light Change in heat Change in gas Chemical reactions and physical changes are sometimes hard to identify

Using Physical and Chemical Properties Products with different properties of reactants often happen in a chemical reaction When iron rusts, a chemical reaction has occurred because the properties of rust are different than iron (melting point, density, reaction with oxygen, conduction of electricity) Combustibility = chemical property of burning Acids and bases are in many solutions. Indicators can determine the strength of acids and bases by reacting chemically and turning different colors. Can be used to separate mixtures or identify substances in mixtures

Using Physical and Chemical Properties Mining companies separate mixtures to make them into useful products Ore = combination of metals and other substances Magnets can be used to separate magnetic substances Some liquid mixtures can be separated by spinning at very high speeds (heavy blood cells from plasma; light cream from heavier milk) Boiling can separate a solid from a liquid (salt from salt water or distillation {collecting water vapor and condensing it}) Sometimes both physical and chemical changes are used

Conservation of Matter Law of conservation of matter = no matter how much physical changes or chemical reactions change the look of matter, the amount of matter stays the same Physical Change - One piece of paper cut up is not more paper; water boiled may appear to be more matter because the water vapor takes up more volume, however the mass stays the same Chemical Change – Mass of the products equals the mass of the reactants The mass in chemical changes may be harder to measure than mass in a physical change