2. Chemistry The study of the properties of matter and how matter changes. Element – a substance that cannot be broken down into any other substances by chemical or physical means. All the matter around you is composed of one element or a combination of elements.

3. Compound – a combination of two or more elements chemically combined in a specific ratio or proportion. Mixture – made from two or more pure substances (elements, compounds, or both) that are combined in the same place, but do not form a new substance. Solution – a well mixed mixture.

4. Changes in Matter Physical change – a change that alters the appearance of a substance, but does not create a new substance. Chemical change – a change in matter that produces a new substance.

5. Observing Chemical Reactions Precipitate – a solid that forms from a solution. The key characteristics of a chemical reaction is the production of new materials that are chemically different from the starting materials.

6. Reactions on a small scale Atom – the smallest particle of an element. Molecule – Two or more atoms combined. Chemical reactions occur when chemical bonds are either formed or broken apart.

7. Describing Chemical Reactions Chemical equations – A shorter easier way to describe a chemical reaction using symbols. Symbol – represents an element. Chemical Formula – shows the ratio of elements in a compound. Subscript – a number on the lower right side of an elements symbol showing how many atoms of an element there are.

8. Structure of an Equation Reactant + Reactant  Product + Product Reactant – the elements you have at the beginning of a reaction. Product – the different materials you end up with after a reaction.

9. Conservation Of Mass The amount of matter in a chemical reaction does not change, so the total mass of the reactants must equal the mass of the products. This leads us to the process of balancing equations.

10. Classifying Chemical Reactions Synthesis – When two or more substances combine to make a more complex substance. + sign on the left of the arrow. Decomposition – breaks down compounds into simpler substances. + sign is on the right. Replacement – one element replaces another in a compound or when two compounds trade places. +sign is on both sides.

11. Controlling Chemical Reactions Every chemical reaction involves a change of energy. Some reactions release energy, some absorb it. Exothermic Reaction – A release of energy in the form of heat. Endothermic Reaction – a reaction that absorbs heat.

12. Getting Reactions Started Activation energy – the energy required to get a chemical reaction started.

13. Rates of Chemical Reactions Concentration – the amount of one material in a given volume of another material. Surface area – amount of particles in a solid available to be in contact with a liquid or gas. Temperature – adding heat to increase the rate of a chemical reaction. Catalyst – a substance added to a chemical reaction to increase the rate of reaction. Inhibiter – a substance added to a chemical reaction to slow the rate of reaction.

14. Fire Safety components of fire- Heat Fuel Oxygen The three things necessary to start and maintain a fire.

15. Preventing Trouble The best way to prevent fires is fire safety. Combustion – a rapid reaction between oxygen and fuel. Fuel – a substance that releases energy in the form of heat when it burns.