Slide 1 of 25 Chemistry 18.1

© Copyright Pearson Prentice Hall Slide 2 of 25 Rates of Reaction The heat given off by the corrosion reaction of an iron- magnesium alloy with salt water can produce a hot meal. The rate of reaction is increased by adding salt water, so heat is produced rapidly. You will learn some ways in which the rate of a reaction can be increased. 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 3 of 25 Collision Theory How is the rate of a chemical change expressed? 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 4 of Collision Theory In chemistry, the rate of chemical change, or the reaction rate, is usually expressed as the amount of reactant changing per unit time.

Slide 5 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction 18.1 Collision Theory A rate is a measure of the speed of any change that occurs within an interval of time.

© Copyright Pearson Prentice Hall > Rates of Reaction Slide 6 of 25 Collision Theory Rates of chemical reactions are often measured as a change in the number of moles during an interval of time. 18.1

Slide 7 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Collision Theory According to collision theory, atoms, ions, and molecules can react to form products when they collide with one another, provided that the colliding particles have enough kinetic energy. 18.1

© Copyright Pearson Prentice Hall > Rates of Reaction Slide 8 of 25 Collision Theory Effective Collision 18.1

© Copyright Pearson Prentice Hall > Rates of Reaction Slide 9 of 25 Collision Theory Ineffective Collision 18.1

Slide 10 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Collision Theory The minimum energy that colliding particles must have in order to react is called the activation energy. 18.1

Slide 11 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Collision Theory An activated complex is an unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier. The activated complex is sometimes called the transition state. 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 12 of 25 Factors Affecting Reaction Rates What four factors influence the rate of a chemical reaction? 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 13 of 25 Factors Affecting Reaction Rates The rate of a chemical reaction depends upon temperature, concentration, particle size, and the use of a catalyst. 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 14 of 25 Factors Affecting Reaction Rates Animation 22 Explore several factors that control the speed of a reaction.

Slide 15 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Factors Affecting Reaction Rates Temperature Storing foods in a refrigerator keeps them fresh longer. Low temperatures slow microbial action. 18.1

Slide 16 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Factors Affecting Reaction Rates Concentration a. In air, a lighted splint glows and soon goes out. b. When placed in pure oxygen (higher oxygen concentration), the splint bursts into flame. 18.1

Slide 17 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Factors Affecting Reaction Rates Particle Size The minute size of the reactant particles (grain dust), and the mixture of the grain dust with oxygen in the air caused the reaction to be explosive, destroying the grain elevator. 18.1

Slide 18 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Factors Affecting Reaction Rates Catalysts 18.1

© Copyright Pearson Prentice Hall Rates of Reaction > Slide 19 of 25 Factors Affecting Reaction Rates Simulation 23 Explore the effects of concentration, temperature, and a catalyst on reaction rate.

Slide 20 of 25 © Copyright Pearson Prentice Hall > Rates of Reaction Factors Affecting Reaction Rates An inhibitor is a substance that interferes with the action of a catalyst. Antioxidants and antimicrobials used in drying fruits and preserving fruit juices slow the action of microbes and limit contact with air. 18.1

END OF SHOW