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RHS SCIENCE TAKS REVIEW PROPERTIES OF MATTER Part 2 ATOMS • Atomic structure Protons + charge in nucleus Neutrons no charge in nucleus Electrons negative charge surround nucleus ATOMS • Atoms of the same element have the same number of protons • Atomic Number # of protons • Mass Number protons + neutrons Think about it . . . What atom has 23 protons? sodium An atom has 15 protons and a mass number of 33. How many neutrons are in the atom? 18 Elements Compounds Mixtures • Elements » Are the the purest substances on earth » Substances made of only one type of atom Each with the same Elements Compounds Mixtures • Compounds » Contain 2 or more elements in fixed proportions » Has different properties than it’s elements » Examples: water, table salt, carbon dioxide, sugar Elements Compounds Mixtures • Mixture » Contain 2 or more substances in variable quantities » Each component retains it’s properties » Ex: milk, dirt, ice tea Check For Understanding Classify each of the following as a element, compound or mixture C M E 1. distilled water 2. river water 3. oxygen and hydrogen Chemical Vs. Physical Change • Chemical Change » occurs when the chemical properties of a substance change » the identity of the substance changes » need energy, such as heat, light, or electricity, to happen. Chemical Vs. Physical Change • Physical Change » When a substance is changed physically » No new substances are formed » Ex: cut, melt, freeze, mix, dissolve, boil, evaporate Chemical Vs. Physical Change • Physical Change » Includes changes in state Check For Understanding Classify each of the following as a chemical a physical change P C C 1. formation of rain 2. cooking a steak 3. rusting or