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CLASSIFYING MATTER Substance (pure): made up of only one kind of matter; every particle has the same fixed composition and properties 1. a. Elements Au, Na, He, N b. Compounds: a substance that contains two or more elements chemically combined in a fixed proportion. C6H12O6, H2O Compounds can be broken down into simpler substances by chemical means. Elements cannot. The properties of a compound are different from the properties of the elements from which it was created – e.g. NaCl CLASSIFYING MATTER 2. Mixture: physical blend of two or more components. Example: salt-sand mixture The basic identity of each substance is not changed. Properties are not the same throughout. Can be separated into its components by physical processes. TYPES OF MIXTURES Heterogeneous: composition is not uniform throughout. Often components are large enough to be seen. Example: Pizza Homogeneous: constant composition throughout, but the amount of each substance can vary. Examples: sugar water, vinegar Solutions: liquid or gaseous mixtures Alloys: solid solutions of metals Examples: steel, brass, bronze LABEL AS SUBSTANCE OR MIXTURE: IF SUBSTANCE, ELEMENT OR COMPOUND? IF MIXTURE, HETERO- OR HOMOGENEOUS? 1. Salt water 2. vinegar 3. sugar 4. sodium 5. orange juice & pulp 6. blood 7. hamburger 8. aluminum foil 9. iron 10. air PHYSICAL CHANGE Physical Change: a change in matter that does not involve a change in the identity of individual substances. Dissolving Changes in state CHEMICAL CHANGE Chemical Change (Chemical Reaction): the change of one or more substances into new substances. REACTANTS PRODUCTS Involves the rearrangement of atoms. Law of Conservation of Mass: no atoms are created or destroyed during a chemical reaction. Mass of Reactants = Mass of Products LABEL AS A “PHYSICAL” OR “CHEMICAL” CHANGE. change in shape - physical rusting of iron - chemical explode - chemical cutting a sheet of paper – physical breaking a crystal – physical corrode - chemical Bend - physical Oxidize - chemical tarnish – chemical grind - Physical melt - physical boil - physical ferment - chemical salt dissolving in water - - physical RECOGNIZING CHEMICAL CHANGES Transfer of Energy -- Heat or Light is released or absorbed. Change in Color (drastic) Production of a Gas (excluding changes in physical state and dissolved gases – e.g. opening a carbonated soda) Formation of a Precipitate (a solid that forms and settles out of a liquid mixture – e.g. soap scum)