S ECTION 7–4: R EACTION R ATES Physical Science Coach Kelsoe Pages 212–215

O BJECTIVES Interpret chemical equations in terms of reactants, products, and conservation of mass. Balance chemical equations by manipulating coefficients. Convert between moles and mass of a substance using molar mass. Calculate amounts of reactants or products by using molar mass, mole ratios, and balanced chemical equations.

R EACTIONS O VER T IME A reaction rate is the rate at which reactants change into products over time. Reaction rates tell you how fast a reaction is going.

Reaction rates do NOT tell you how fast ______. A: substances are changing state In general, if the temperature of a chemical reaction is increased, the reaction rate _______. A: increases A log is burning in a fireplace. If the amount of oxygen reaching the log is decreased, which of the following statements is true? A: the reaction rate decreases.

Measuring how quickly a reactant disappears is one way to measure the rate of the reaction. A chunk of limestone, which is calcium carbonate, reacts with acid at a certain rate. If the limestone were crushed, the rate of reaction between the acid and limestone would increase. A catalyst is used in a catalytic converter in vehicles to help control pollution. For example, the catalytic converter speeds up the rate at which carbon monoxide is oxidized to carbon dioxide. (2CO + O 2  2CO 2 )

V OCABULARY Reaction rate Catalyst

S TUDY G UIDE #21-23, should be completed.

S ECTION 7–5: E QUILIBRIUM Physical Science Coach Kelsoe Pages 216–219

O BJECTIVES Interpret chemical equations in terms of reactants, products, and conservation of mass. Balance chemical equations by manipulating coefficients. Convert between moles and mass of a substance using molar mass. Calculate amounts of reactants or products by using molar mass, mole ratios, and balanced chemical equations.

When the forward and reverse paths of a change occur at the same rate, A: the system is in equilibrium. The equation 2NO 2  N 2 O 4 shows a system ____. A: in chemical equilibrium. The reaction H 2 CO 3 + H 2 O  H 3 O + + HCO 3 - takes place in water. What happens to the equilibrium when the pressure is increased? A: it does not change.

The statement that when a change is introduced to a system in equilibrium, the equilibrium shifts in the direction that relieves the stress on the system is known as Le Chatelier’s principle. Many manufacturing processes involve chemical reactions that reach equilibrium. One way to increase the amount of product formed is to decrease the concentration of the product in the system.

V OCABULARY Equilibrium Reversible reaction

S TUDY G UIDE #24-26, should be completed.