1. Chapter 6 - KEY CONCEPTS (Page 1)
What is a Chemical Reaction?
Key Concepts:
A physical change, such as a state change or dissolving, does not create a new substance, but a chemical change does.
In a chemical reaction, the atoms and molecules that interact with each other are called reactants.
In a chemical reaction, the atoms and molecules produced by the reaction are called products.
In a chemical reaction, only the atoms present in the reactants can end up in the products. No new atoms are created, and no atoms are destroyed.
In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.
Controlling the Amount of Products in a Chemical Reaction
Key Concepts
Changing the amount of reactants affects the amount of products produced in a chemical reaction.
In a chemical reaction, only the atoms present in the reactants can end up in the products.
Mass is conserved in a chemical reaction.
Forming a Precipitate
The ions or molecules in two solutions can react to form a solid.
A solid formed from two solutions is called a precipitate.
Temperature and the Rate of a Chemical Reaction
Reactants must be moving fast enough and hit each other hard enough for a chemical reaction to take place.
Increasing the temperature increases the average speed of the reactant molecules.
As more molecules move faster, the number of molecules moving fast enough to react increases, which results in faster formation of products.

2. Chapter 6 - KEY CONCEPTS (Page 2)
A Catalyst and the Rate of Reaction
Key Concepts
A catalyst is a substance that can help the reactants in a chemical reaction react with each other faster.
A catalyst does not actually become part of the products of the reaction.
Using Chemical Change to Identify an Unknown
Substances react chemically in characteristic ways
A set of reactions can be used to identify an unknown substance
Energy Changes in Chemical Reactions
If two substances react and the temperature of the mixture decreases, the reaction is endothermic.
If two substances react and the temperature of the mixture increases, the reaction is exothermic.
A chemical reaction involves the breaking of bonds in the reactants and the forming of bonds in the products.
It takes energy to break bonds.
Energy is released when bonds are formed.
If a reaction is endothermic, it takes more energy to break the bonds of the reactants than is released when the bonds of the products are formed.
If a reaction is exothermic, more energy is released when the bonds of the products are formed than it takes to break the bonds of the reactants.

3. Chapter 6 - KEY CONCEPTS (Page 3)
pH and Color Change
Key Concepts
Whether a solution is acidic or basic can be measured on the pH scale.
When universal indicator is added to a solution, the color change can indicate the approximate pH of the solution.
Acids cause universal indicator solution to change from green toward red.
Bases cause universal indicator to change from green toward purple.
Water molecules (H2O) can interact with one another to form H3O+ ions and OH− ions.
At a pH of 7, there are equal numbers of H3O+ ions and OH− ions in water, and this is called a neutral solution.
Acidic solutions have a pH below 7 on the pH scale.
Basic solutions have a pH above 7 on the pH scale.
Neutralizing Acids and Bases
pH is a measure of the concentration of H3O+ ions in a solution.
Adding an acid increases the concentration of H3O+ ions in the solution.
Adding a base decreases the concentration of H3O+ ions in the solution.
An acid and a base are like chemical opposites.
If a base is added to an acidic solution, the solution becomes less acidic and moves toward the middle of the pH scale. This is called neutralizing the acid.
If an acid is added to a basic solution, the solution becomes less basic and moves toward the middle of the pH scale. This is called neutralizing the base.
Carbon Dioxide Can Make a Solution Acidic
Carbon dioxide (CO2) gas dissolved in water can cause water to become acidic.
The acidity of water from dissolved CO2 can be reduced by a base such as baking soda (sodium bicarbonate).

4. CHEMICAL CHANGE
A chemical change is different than a physical change because in a chemical change a new substance is formed and in a physical change no new substance is formed.

5. CHEMICAL CHANGE
One clue of a chemical change is the formation of a precipitate.
A precipitate is formed when two liquids react and a solid is formed.

6. CHEMICAL REACTION
In a chemical reaction, mass is conserved. This means that the type and number of atoms in the reactants equals the type and number of atoms in the products.
Two molecules are more likely to react if they have more energy when they collide.
In a chemical reaction the atoms of the reactants unbond, rearrange, and then rebond to form the products.
Dissolving salt is not a chemical reaction.
This means that in a chemical reaction, the atoms in the reactants are the only atoms that can end up in the products. All the different types and numbers of atoms in the reactants end up in the products.

7. CHEMICAL REACTION
If more reactants are used in a chemical reaction, more products will be produced. This is because more reactants have more atoms to react to form more products.
Substances react chemically in characteristic ways. This means a substance will always react the same way when tested with the same chemical. Because substances react chemically in characteristic ways, you can use the way they react to identify an unknown.
In a chemical reaction, if the reactants are heated, the reaction usually happens faster.
In a combustion reaction matter is not destroyed.
Some chemical reactions requires substance called a catalyst. The main purpose of a catalyst is to speed up the reaction. A catalyst does not actually become part of the products of a chemical reaction.

8. EXOTHERMIC vs ENDOTHERMIC If a reaction is exothermic more energy is released when the bonds in the product are formed than is used to break the bonds in the reactants. If the reaction is endothermic it takes more energy to break the bonds of the reactants than is released when the bonds in the products are formed.

9. In any sample of water, there are always some water molecules which have become ions. These ions are produced by transferring a proton from one water molecule to another.

10. pH
The number on the pH scale decreases when the pH of a solution becomes more acidic.
The number on the pH scale increases when the pH of a solution becomes more basic.
If a solution is acidic, it can be neutralized by adding a base.
If a solution is basic, it can be neutralized by adding an acid.