Chapter 6 Chemical Reactions

Section 1Observing Chemical Change

I. Properties and Changes in Matter

1. Matter – Anything that has mass and takes up space.2. Chemistry – the study of matter and how matter changes.3. Physical Properties – characteristics that can be observed without changing the substance into another substance.

Examples:

Color, temperatures for phase changes, texture, whether it dissolves in water, and how well it conducts heat and electricity.

4. Chemical Property – characteristics of a property that describe its ability to change into other substances.

Examples:

Flammability, rusting, tarnishing.5. Precipitate – A solid that forms from a solution during a chemical reaction. 6. Endothermic reaction – a reaction in which energy is absorbed.

Example: baking soda and vinegar, making pancakes.

7. Exothermic reactions- a reaction in which energy is released.

Examples: Combustion, hand warmers.

Chapter 6 ~ Section 2

Describing Chemical Reactions

1. Chemical Equation: a way to describe a chemical reaction using symbols instead of words.

2. Reactant: the substances you have at the beginning of a chemical equation.

3. Product: the new substances you have at the end of the equation.

H2 + O2 H2O Reactants Products

4. Conservation of Mass: in a chemical reaction, the total mass of the reactants must equal the total mass of the products.

5. Open System: A system where matter can enter or leave. Example: Fireplace

6. Closed System: A system where no matter can enter or leave.

Example: Sealed plastic bag, closed beaker/flask.

7. Coefficient: A number placed in front of a formula in an equation.

2H2 + O2 2H2O

Coefficients

8. Synthesis: when two or more elements or compounds combine to make a new substance. Example: Hydrogen and Oxygen making water.

9. Decomposition: when a compound breaks down into simpler substances. Example: Hydrogen Peroxide breaking down into water and oxygen gas.

10. Replacement: When an element replaces another element in a compound or when elements in different compounds trade places.

Balancing Equations

Cu + O2 CuO

Balancing Equations

Cu + O2 CuO

Balancing Equations

2Cu + O2 2CuO

A tougher example.

CH4 + O2 CO2 + H20

A tougher example.

CH4 + O2 CO2 + H20

A tougher example.

CH4 + O2 CO2 + H20

A tougher example.

CH4 + 2O2 CO2 + 2H20

H2SO4 + NaOH H2O + Na2SO4

H2SO4 + 2NaOH 2H2O + Na2SO4