Do NowNow that you know a little about chemical reactions, think about the many chemical reactions that take place around you every day. Describe your favorite chemical reaction. How do you think energy is involved in the reaction?

Write your answer in your science journal.

Quiz1. How many molecules of oxygen gas in the reactant (O2) are needed to balance this equation?

CH4 + O2 → 2CO2 + 4H2O

2. Which way does heat move?

3. The Chemical formula for carbon dioxide is CO2. What does the formula show about each element in the compound?

4. Which changes of state cause an increase in the kinetic energy of the particles?

Objectives:Students will compare exothermic and endothermic reaction by interpreting an energy diagram and describing the factors that affect the rate of a reaction.

Agenda

Today we will:

Teacher presentation on energy and rates of reactions.

Group reading and discussion

Exit ticket

Vocabulary• exothermic• endothermic• law of conservation of

energy• temperature• concentration• surface area• inhibitor• catalyst

Today I will: Learn about how energy can affect the rate of a chemical reaction.So that I can: Apply that knowledge to different chemical reactions.I will know I got it if:I can interpret an energy diagram and list 5 factors that affect the rate of a reaction.

Objectives

• Compare exothermic and endothermic reactions.

• Explain activation energy.

• Interpret an energy diagram.

• Describe five factors that affect the rate of a reaction.

Do Now

What are three ways to increase (make faster) the rate of a chemical reaction?

¿Cuáles son tres maneras de aumentar (hacer más rápido) la velocidad de una reacción química?

Quais são as três maneiras de aumentar (fazem mais rápido) a velocidade de uma reação química?

Mi az a három módon lehet növelni (gyorsabb) mértéke egy kémiai reakció?

Agenda

Today we will:Work in centers.

Center 1: Video discussing chemical reaction with worksheet.

Center 2: Gizmo on chemical reactions.Center 3: Lab creation involving the method

of increasing a chemical reaction.

Vocabulary exothermic endothermic rate of reaction temperature concentration surface area catalyst inhibitor

What Is Temperature?

• Temperature is a measure of the average kinetic energy of the particles in an object.

• Kinetic energy is the energy of motion. All moving objects have kinetic energy.

• The amount of kinetic energy that an object has depends on the object’s mass and speed.

What Is Temperature?, continued

• Temperature and Kinetic Energy All matter is made of atoms or molecules that are always moving.

• The faster the particles are moving, the more kinetic energy they have. The more kinetic energy the particles of an object have, the higher the temperature of the object is.

Section 1 Three States of MatterChapter K2

What Is Temperature?, continued

• The gas particles on the right have a higher average kinetic energy than those on the left. So, the gas on the right is at a higher temperature.

What Is Temperature?, continued

• Average Kinetic Energy of Particles The motion of particles in matter is random, so individual particles have different amounts of kinetic energy.

• When you measure an object’s temperature, you are measuring the average kinetic energy of the particles in the object.

Transferred Thermal Energy

• Heat is the energy transferred between objects that are at different temperatures.

• When two objects at different temperatures come into contact, energy is always transferred from the object that has the higher temperature to the object that has the lower temperature.

Transferred Thermal Energy, continued

• Heat and Thermal Energy Heat is transferred in the form of thermal energy. Thermal energy is the total kinetic energy of the particles that make up a substance.

• Thermal energy depends partly on temperature. Thermal energy also depends on how much of a substance there is.

Transferred Thermal Energy, continued

• Reaching Thermal Equilibrium The point at which two object that are touching reach the same temperature is called thermal equilibrium.

• When objects that are touching have the same temperature, they are at thermal equilibrium and no net change in the thermal energy of either one occurs.

Conduction, Convection, and Radiation

• Thermal Conduction is the transfer of thermal energy from one substance to another through direct contact. Conduction can also occur within a substance.

• The particles of substances as different temperatures have different average kinetic energies. When such substances touch, their particles collide.

Conduction, Convection, and Radiation, continued

• When particles collide, particles with higher kinetic energy transfer energy to those with lower kinetic energy.

• This transfer of energy happens until all particles have the same average kinetic energy. As a result, the substances have the same temperature.

Conduction, Convection, and Radiation, continued

• Conductors and Insulators Substances that conduct thermal energy well are called thermal conductors. Most metals are thermal conductors.

• Substances that do not conduct thermal energy well are called thermal insulators. Wood and plastic are examples of thermal insulators.

Section 3 Changes of StateChapter K2

Increase in Kinetic energy: melting, boiling, evaporation sublimation

Decrease in kinetic energy: condensation, freezing, deposition

Section 3 Changes of StateChapter K2

Reactions and Energy

•By comparing the chemical energy of the reactants with the chemical energy of the products, you can decide if energy is released or absorbed in the reaction.

• Exothermic Reactions are reactions in which energy is released. Energy can be released as light, electrical energy, or thermal energy.

Reactions and Energy, continued

• Endothermic Reactions are reactions in which energy is taken in.

• The Law of Conservation of Energy states that energy cannot be created or destroyed. The energy released in exothermic reactions was first stored in the chemical bonds of the reactants. And the energy taken in during endothermic reactions is stored in the products.

Rates of Reactions

• The speed at which new particles form is called the rate of a reaction.

• Activation Energy is the smallest amount of energy that molecules need to react. A chemical reaction needs a boost of energy greater than or equal to the activation energy before the reaction can start.

Rates of Reactions, continued

• Sources of Activation Energy Friction is one source of activation energy. In a match, friction provides the energy needed to break the bonds in the reactants and allow new bonds to form.

• An electric spark in a car’s engine is another source of activation energy. This spark begins the burning of gasoline.

• Light can also be a source of activation energy for a reaction.

Rates of Chemical Reactions

5 Factors Affecting Rates of

Reactionstemperatureconcentrationsurface areainhibitorscatalysts

Factors Affecting Rates of Reactions

• Temperature A higher temperature causes a faster rate of reaction. At high temperatures, particles of reactants move quickly and collide hard and often.

• At low temperatures, particles move slowly and collide less often.

Factors Affecting Rates of Reactions, continued

•Concentration In general, a high concentration of reactants causes a fast rate of reaction. Concentration is a measure of the amount of one substance when it is dissolved in another substance.

• When concentration is high, there are many reactant particles in a given volume. So, there is little distance between particles and the particles collide more often and react faster.

Factors Affecting Rates of Reactions, continued

• Surface Area is the amount of exposed surface of a substance. Increasing the surface area of solid reactants increases the rate of a reaction.

• Inhibitors are substances that slow down or stop a chemical reaction. The rate of a reaction decreases in the presence of an inhibitor.

Factors Affecting Rates of Reactions, continued

• Catalysts are substances that speed up a reaction without being permanently changed. Because it is not changed, a catalyst is not a reactant.

• A catalyst lowers the activation energy of a reaction, which allows the reaction to happen more quickly.

• Catalysts called enzymes speed up most reactions in your body.

Exit Ticket