2. P HYSICAL P ROPERTIES Physical property – characteristic that can be observed without changing the composition of a substance Appearance includes things that can be observed with the senses States of matter – solid, liquid, or gas Volume, mass, and density Melting point, boiling point, and others

3. C HEMICAL PROPERTIES Chemical property – characteristic that cannot be observed without altering the substance Ability to burn Tendency to rust Reaction to other substances such as acids and bases

4. P HYSICAL CHANGES Physical change – form or appearance of matter changes, but composition stays the same. Change does not produce a new substance Shape can change, but substance does not Dissolving a solid into a liquid is a physical change

5. C HEMICAL CHANGES Chemical change: a change in the substance’s composition During a chemical reaction: Energy may be gained or released Color can change Substances may change odor Formation of a gas or the precipitation of a solid

9. C HEMICAL REACTION Chemical Reaction – one or more substances are changed into a new substance, with new physical and chemical properties. Chemical Changes result in a new substance with a new chemical formula

10. S IGNS OF A CHEMICAL CHANGE Heat is released or absorbed, measured by a temperature change Unexpected color change Release of a gas odor, steam, or bubbles Formation of a precipitate when a solid forms from reacting liquids

11. C HEMICAL EQUATION Chemical Equation – represents the chemical combining of elements and/or compounds (reactants and their products) Reactants – substances that are about to react on the left of an equation. Products - the new substance(s) that are produced on the right Reactants yield Products

12. C HEMICAL EQUATION CONTINUED Coefficient – number that indicates how many compounds or elements are present in chemical reaction, written in front of the formula or symbol. Subscript – smaller number written after a symbol that tells how many atoms are present in a compound

13. R EVIEW CHEMICAL EQUATION CH 4 + 2 O 2 → CO 2 + 2 H 2 O 1. What are the reactants? 2. What are the products? 3. What is the term for the small 4 by the CH 4 and what does it mean? 4. How many oxygen atoms are reactants? 5. How many oxygen atoms are products? 1. CH 4 2O 2 2. CO 2 2H 2 O 3. Subscript, there are 4 Hydrogen atoms 4. 4 5. 4

14. L AW OF CONSERVATION OF MASS The mass of the products of a chemical reaction must be the same as the mass of the reactants in that reaction. The number and kind of atoms must be equal on both sides of the equation. Atoms are never lost or created in a chemical reaction; however, they do change partners.

15. E NERGY REACTIONS

16. E XOTHERMIC R EACTIONS Therm refers to heat energy Exo refers to out Exothermic reaction a reaction in which energy is released during the reaction. The products have less energy than the reactants. Exothermic reactions feel warm Energy is written on the product side of the equation.

17. E NDOTHERMIC REACTIONS Endo refers to in Reaction in which energy is absorbed during the reaction. The products have more energy than the reactants. Endothermic reactions feel cold Energy is written on the reactant side of the equation.