WHAT IS A CHEMICAL REACTION? A chemical reaction is what happens when there is a chemical change. A chemical change is when a new substance is formed or made.

WHAT IS A CHEMICAL REACTION? A chemical reaction is what happens when there is a chemical change. A chemical change is when a new substance is formed or made. In a chemical reaction, chemical bonds are made or broken. The new bonds make a new substance.

HOW DO WE DESCRIBE WHAT IS HAPPENING IN A CHEMICAL REACTION? Chemical equations are used to show what is happening in chemical reactions.

HOW DO WE DESCRIBE WHAT IS HAPPENING IN A CHEMICAL REACTION? Chemical equations are used to show what is happening in chemical reactions. Chemical equations are like recipes in cooking or addition problems in math.

HOW DO WE DESCRIBE WHAT IS HAPPENING IN A CHEMICAL REACTION? Chemical equations are used to show what is happening in chemical reactions. Chemical equations are like recipes in cooking or addition problems in math. A chemical equation describes a chemical reaction using chemical formulas for the reactants and products.

HOW DO WE DESCRIBE WHAT IS HAPPENING IN A CHEMICAL REACTION? Chemical equations are used to show what is happening in chemical reactions. Chemical equations are like recipes in cooking or addition problems in math. A chemical equation describes a chemical reaction using chemical formulas for the reactants and products. Example: magnesium burning. The chemical equation is: 2Mg + O 2 —› 2MgO

WHAT ARE REACTANTS AND PRODUCTS? REACTANTS are the substances you put into the reaction before the reaction happens (the ingredients). Reactants are the substances that are going to be changed by the chemical reaction.

WHAT ARE REACTANTS AND PRODUCTS? REACTANTS are the substances you put into the reaction before the reaction happens (the ingredients). Reactants are the substances that are going to be changed by the chemical reaction. PRODUCTS are the new substances created by the reaction after the chemical reaction happens.

WHAT ARE REACTANTS AND PRODUCTS? REACTANTS are the substances you put into the reaction before the reaction happens (the ingredients). Reactants are the substances that are going to be changed by the chemical reaction. PRODUCTS are the new substances created by the reaction after the chemical reaction happens. Products are what you make. Reactants – before the chemical reaction (on the left). Products – after the chemical reaction (on the right).

WHAT IS THE LAW OF CONSERVATION OF MASS? Mass (or matter) is never created or destroyed in a chemical reaction.

WHAT IS THE LAW OF CONSERVATION OF MASS? Mass (or matter) is never created or destroyed in a chemical reaction. However, mass (or matter) can be changed into a different substance or state.

BALANCING CHEMICAL EQUATIONS Because mass is never created or destroyed in a chemical reaction, chemical equations must be balanced to show the same number of atoms before the reaction and after the reaction.

BALANCING CHEMICAL EQUATIONS Because mass is never created or destroyed in a chemical reaction, chemical equations must be balanced to show the same number of atoms before the reaction and after the reaction. To balance an equation, you will have to change or adjust the coefficients or the numbers in front of a reactant or product. YOU CANNOT CHANGE THE NUMBERS IN BACK.

Equation Analogy Imagine that you work at a skateboard shop and you are in charge of assembling the skateboards. Every skateboard requires one deck (the board), two trucks (the mounted axles), and four wheels. 1.Your boss asks you to make five skateboards. How many trucks do you need? 2.The following diagram shows the “recipe” for one skateboard. What do you notice about the relative amounts of each part on either side of the arrow?

COMBUSTION REACTION Combustion or “burning” is when a substance rapidly reacts with oxygen, producing heat and light. Example: CH 4 + 2O 2 —› CO 2 + 2H 2 O Example: 2Mg + O 2 —› 2MgO

CHEMICAL BONDS AND ENERGY Chemical energy is stored in chemical bonds. Chemical reactions break bonds and make bonds. This breaking and forming of bonds releases chemical energy.

CHEMICAL BONDS AND ENERGY Chemical energy is stored in chemical bonds. Chemical reactions break bonds and make bonds. This breaking and forming of bonds releases chemical energy. Breaking bonds takes energy.

CHEMICAL BONDS AND ENERGY Chemical energy is stored in chemical bonds. Chemical reactions break bonds and make bonds. This breaking and forming of bonds releases chemical energy. Breaking bonds takes energy. Forming bonds releases energy.

EXOTHERMIC REACTIONS “Exo-” means out. In an exothermic reaction, energy is released or comes out of the reaction.

EXOTHERMIC REACTIONS “Exo-” means out. In an exothermic reaction, energy is released or comes out of the reaction. The energy released from the formation of bonds is greater than the energy needed to break the bonds.

EXOTHERMIC REACTIONS “Exo-” means out. In an exothermic reaction, energy is released or comes out of the reaction. The energy released from the formation of bonds is greater than the energy needed to break the bonds. More energy comes out than you put in – gets hot.

EXOTHERMIC REACTIONS “Exo-” means out. In an exothermic reaction, energy is released or comes out of the reaction. The energy released from the formation of bonds is greater than the energy needed to break the bonds. More energy comes out than you put in. Example: Combustion C 3 H 8 + 5O 2 —› 3CO 2 + 4H 2 O kJ

ENDOTHERMIC REACTIONS “Endo-” means in. In an endothermic reaction, energy is absorbed or taken in by the reaction.

ENDOTHERMIC REACTIONS “Endo-” means in. In an endothermic reaction, energy is absorbed or taken in by the reaction. The energy needed to break the bonds is greater than the energy released by formation of new bonds in the products.

ENDOTHERMIC REACTIONS “Endo-” means in. In an endothermic reaction, energy is absorbed or taken in by the reaction. The energy needed to break the bonds is greater than the energy released by formation of new bonds in the products. More energy goes in than you get out – turns cold. Examples: Photosynthesis: sunlight + 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Cooking: baking soda and vinegar demo

ENDOTHERMIC REACTIONS “Endo-” means in. In an endothermic reaction, energy is absorbed or taken in by the reaction. The energy needed to break the bonds is greater than the energy released by formation of new bonds in the products. More energy goes in than you get out – turns cold. Examples: Photosynthesis: sunlight + 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Cooking: baking soda and vinegar demo

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates:

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates: 1. Temperature: increase in temperature, increase in reaction rate. HEAT IT UP.

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates: 1. Temperature: increase in temperature, increase in reaction rate. HEAT IT UP. 2. Surface area: greater surface area, increase in reaction. Break into pieces. BREAK IT UP.

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates: 1. Temperature: increase in temperature, increase in reaction rate. HEAT IT UP. 2. Surface area: greater surface area, increase in reaction. Break into pieces. BREAK IT UP. 3. Stirring: Stirring increases reaction rate. STIR IT UP.

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates: 1. Temperature: increase in temperature, increase in reaction rate. HEAT IT UP. 2. Surface area: greater surface area, increase in reaction. Break into pieces. BREAK IT UP. 3. Stirring: Stirring increases reaction rate. STIR IT UP. 4. Concentration: increasing particles in a given volume (or decreasing volume) increases reaction. PUMP IT UP.

REACTION RATES A reaction rate is how fast a chemical reaction is happening. Factors that affect reaction rates: 1. Temperature: increase in temperature, increase in reaction rate. HEAT IT UP. 2. Surface area: greater surface area, increase in reaction. Break into smaller pieces. BREAK IT UP. 3. Stirring: Stirring increases reaction rate. STIR IT UP. 4. Concentration: increasing particles in a given volume (or decreasing volume) increases reaction. PUMP IT UP. 5. Catalysts: some substances increase reactions, but are not used up in the reaction. Not reactants and not products. START IT UP.