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Changes. Physical Changes. Physical changes are reversible and do not alter the chemical make-up of a substance Examples Change in state freezing, melting, evaporating, condensing, sublimating Breaking into pieces Chopping wood, tearing paper Mixtures Kool-aid. Chemical Changes.
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Physical Changes • Physical changes are reversible and do not alter the chemical make-up of a substance • Examples • Change in state • freezing, melting, evaporating, condensing, sublimating • Breaking into pieces • Chopping wood, tearing paper • Mixtures • Kool-aid
Chemical Changes • Chemical changes actually change the molecular structure of a substance, irreversible • Combustion, reaction, oxidation • Catalyst – something that causes a change or speeds it up • Reactant – any substance participating in a chemical reaction
How Can You Recognize a Chemical Change? • A new substance is formed (a solid) • A color change • Fizzing or bubbling (a gas is produced) • Light is produced • Temperature Change • Endothermic – change absorbs heat and gets colder • Exothermic – change releases heat and gets hotter
Mixtures • Mixture – A combination of two or more substances, but it does not create a new substance, and it can be separated. Does not have to be blended evenly • Iron filings in sand • Solution – A special mixture formed when one or more materials dissolves in another • Blended evenly • Kool-Aid • Both can be separated in some manner • Magnets, evaporations, straining
Compound • A compoundis made from two or more elements that are chemically combined and is not separated by physical means into other substances. • Examples: • H2O (water) • H2O2 ( hydrogen peroxide) • C6H12O6 (glucose or sugar) • FeO4 (iron oxide or rust)
Practice • Venn Digram • Compare and Contrast