18.1 rates of reaction - mr. walkmrwalk.com/chapter 18 - reaction rates and... · 18.1 rates of...

5/27/2014

1

© Copyright Pearson Prentice Hall

Slide

1 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


Rates of Reaction >

Slide

2 of 25

Collision Theory

Collision Theory

How is the rate of a chemical change

expressed?

18.1

5/27/2014

2


Rates of Reaction >

Slide

3 of 25

18.1 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

4 of 25


>Rates of Reaction18.1 Collision Theory

A rate is a measure of the speed of any change

that occurs within an interval of time.

5/27/2014

3


>Rates of Reaction

Slide

5 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

6 of 25


>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

5/27/2014

4


>Rates of Reaction

Slide

7 of 25

Collision Theory

Effective Collision

18.1


>Rates of Reaction

Slide

8 of 25

Collision Theory

Ineffective Collision

18.1

5/27/2014

5

Slide

9 of 25



The minimum energy that colliding particles

must have in order to react is called the

activation energy.

18.1

Slide

10 of 25



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

5/27/2014

6


Rates of Reaction >

Slide

11 of 25

Factors Affecting Reaction Rates


What four factors influence the rate of a

chemical reaction?

18.1


Rates of Reaction >

Slide

12 of 25


The rate of a chemical reaction depends

upon temperature, concentration,

particle size, and the use of a catalyst.

18.1

5/27/2014

7


Rates of Reaction >

Slide

13 of 25


Animation 22

Explore several factors that control the speed of a

reaction.

Slide

14 of 25


>Rates of Reaction Factors Affecting Reaction Rates

Temperature

Lower temperatures = Slower reactions

Higher temperatures = Faster reactions

Storing foods in a refrigerator keeps them fresh

longer. Low temperatures slow microbial action.

18.1

5/27/2014

8

Slide

15 of 25



Concentration

Higher concentration = faster reactions

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

16 of 25



Particle Size

Smaller Particles = More surface area = faster reactions

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

5/27/2014

9

Slide

17 of 25



Catalysts

Catalysts are substances that increase the rate

of a reaction without being used up during the

reaction.

18.1

Slide

18 of 25



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

18.1 rates of reaction - mr. walkmrwalk.com/chapter 18 - reaction rates and... · 18.1 rates of...

Documents