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Using Chemical Demonstrations to Demonstrate Concepts in Ph Using Chemical Demonstrations to Demonstrate Concepts in Ph

Using Chemical Demonstrations to Demonstrate Concepts in Ph - PowerPoint Presentation

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Using Chemical Demonstrations to Demonstrate Concepts in Ph - PPT Presentation

Holt Science amp Technology Physical Science Chapter 14 Chemical Reactions Section 4 Energy and Rates of Reactions Section Outline Reactions and Energy Exothermic reactions Figure 1 Types of Chemical Reactions ID: 574105

reaction energy reactions chemical energy reaction chemical reactions rates demonstration activation particles concentration figure catalyst affecting factors light surface

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Slide1

Using Chemical Demonstrations to Demonstrate Concepts in Physical Science IISlide2

Holt Science & Technology:Physical ScienceSlide3

Chapter 14 Chemical ReactionsSection 4 Energy and Rates of Reactions

Section Outline

Reactions and Energy

- Exothermic reactions

Figure 1. Types of Chemical Reactions

-Law of Conservation of Energy

Figure 2. No title

Rates of Reaction

- Activation energy

Figure 3. No title

-Sources of Activation Energy

Figure 4. Energy Diagrams

Slide4

Chapter 14 Chemical ReactionsSection 4 Energy and Rates of Reactions

Section Outline (cont.)

Factors Affecting Rate of Reaction

- Temperature

Figure 5. No title

- Concentration

Figure 6. Concentration of solutions

- Catalyst

Figure 7. No title

Slide5

Reactions and EnergyChemical energy is part of all chemical reactions.

Energy is needed to break chemical bonds in reactions.

Energy is released when new chemical bonds form in chemical reactions.

Slide6

Reactions and EnergyExothermic reaction – a chemical reaction that releases energyExo

means “go out” or “exit”

Endothermic reaction – a chemical reaction that takes energy in

Endo

means “go in”Slide7

Demonstration 1 – Energy Release

Types of Energy release

Light

Electrical energy

Light and thermal energySlide8

Demonstration 1 – LightSnapping a glowstick

breaks a small glass container in the

glowstick

, allowing chemicals in the glass container to mix with chemicals outside the glass (but inside the chamber of the

glowstick

).

The resulting reaction gives

off light.Slide9

Demonstration 2 – Electrical Energy

Electrical energy is released in an

exothermic reaction that takes place

in the battery

See if the batteries get warm.

2 MnO

2

(s) + 2 H

2

O(l) + Zn(s)

 2

MnO

(OH)(s) +

Zn(OH)

2(s)Slide10

Demonstration 3 – Heat and Light Release

CH

4

+ 2 O

2

 CO

2

+ 2 H

2

O

Energy is released during some chemical reactions. The fire of a Bunsen burner gives off light energy and chemical energy. (An alcohol burner, candle, lighter, etc. could also be used, although reaction would change.)

Slide11

Signs of Chemical ReactionsGas formationSolid (precipitate) formation

Color change

Energy change

Light

Thermal energy (heat)

Electrical energySlide12

Law of Conservation of EnergyLaw of conservation of energy – energy cannot be created or destroyed

Energy can change forms

Energy can be transferred from one

object to another in the same manner

that a baton is transferred from one

runner to another in a relay race.Slide13

Rates of ReactionActivation energy – smallest amount of energy that molecules need to react.

Chemical reactions need energy to get started

In the same way that a bowling ball needs a push

to get rolling.Slide14

Activation Energy

Reaction progress

Reaction progress

Products

Energy

given

off

Energy

Reactants

Activation energy

Energy

Energy

absorbed

Activation

energySlide15

Factors Affecting Rates of ReactionDemonstration 4 – Glow Sticks

Temperature

A higher temperature causes a faster reaction rate.

At higher T, particles of reactants move rapidly.

Rapid movement causes particles to collide often and with a lot of energy.

Many particles have the activation energy to react and change into products in a short time.

The light stick on the right glows brighter

than the one on the left because the one

on the right is warmer. Slide16

Factors Affecting Rates of Reaction

Concentration

In general, a high concentration of reactants causes a fast rate of reaction.

Concentration is a measure of the amount of one substance dissolved in another substance.

When the concentration is high, there are many reactant particles in a given volume and a small

distance between them.

Thus, the particles run into each

other often, leading particles to react faster.Slide17

Factors Affecting Rates of Reaction

Surface Area

Surface area is the amount of exposed surface of a substance

Increasing surface area increases rate of reaction.

Greater surface area exposes more particles of the reactant to other reactant particles.

These leads to more collisions and faster rates.Slide18

Demonstration 5 – Mentos and Diet Coke

http://www.eepybird.com/featured-video/the-extreme-diet-coke-mentos-experiments-ii-the-domino-effect//Slide19

Factors Affecting Rates of Reaction

Inhibitors

An inhibitor is a substance that slows down or stops a reaction

Food preservatives – slow down growth of bacteria and fungiSlide20

Factors Affecting Rates of Reaction

Catalysts

Catalyst – speeds up a chemical reaction without being consumed/

A catalyst is not consumed because it is not a reactant.

A catalyst lowers the activation barrier, which allows a reaction to happen more quickly.

This catalytic converter contains platinum and

palladium. These two catalysts increase the rate

of reactions that make the car’s exhaust less

harmful.Slide21

Demonstration 6 – CatalystHydrogen peroxide, H

2

O

2

, is unstable but decomposes very slowly. The decomposition reaction gives off heat. If Cu

2+

ions are added (as a catalyst) to add aqueous solution of H

2

O

2

, the reaction proceeds rapidly and can become hot enough to boil the water.

If dishwashing detergent is added to the solution before the catalyst, then a version of the elephant toothpaste demonstration is produced.

2 H

2

O2  O2 + 2 H2O Slide22

Demonstration 7 – Clock ReactionConcentration, temperature, inhibitorSlide23

Demonstration 8 – Alka Seltzer

Concentration, temperature, surface area