Chemistry in Action

Key Terms

Synthesis

Decomposition

Polymerisation

Collision Theory

Kinetic Energy

Catalyst

Enzyme

Substrate

Active Site

Surface Area

Types of Chemical Reaction

Types of Chemical Reaction

Synthesis Using two products to create something new.

For example:

2H2 + O2 2H2O

Types of Chemical Reaction

Types of Chemical Reaction

Decomposition A substance is broken down to simpler products.

For example:

CaCO3 CaO + CO2

OR

2H2O 2H2 + O2

Types of Chemical Reaction

Types of Chemical Reaction

Types of Chemical Reaction

Polymerisation

A large number of monomers (single parts) are joined together to form a long chain called a polymer (many parts).

High density polymers have little branching.

Low density polymers have a lot of branching.

Reaction Rates

Controlling Reaction Rates

There are a number of things we can do to control the rate of a reaction.

When designing a process chemists need to consider: Should the reaction go quickly or slowly?

What would be the costs involved in controlling the reaction rate?

Are there any safety or environmental concerns?

More particles colliding leads to more reactions.

Collision Theory

Collision Theory

The particles must have the correct orientation.

Collision Theory

Collision Theory

The particles must have enough energy to bring about a reaction.

Collision Theory

Increasing Reaction Rate

Increased temperature Leads to increased frequency of collisions

Particles have greater kinetic energy

Increasing Reaction Rates

Increasing Reaction Rates

Increasing concentration of reactants. Leads to increased frequency of collisions

NOTE: Increasing the pressure of a gas is equivalent to increasing concentration of reactants.

Increasing Reaction Rates

Use of catalysts. Lowers the activation energy.

NOTE: Catalysts do not change during the reaction. They only facilitate it.

Increasing Reaction Rates

Haaaaave you met Ted?

Increasing Reaction Rates

Increasing Reaction Rate

Enzymes A special category of biological

catalysts.

They are proteins so they only work in certain pH and temperature ranges.

Enzymes are very specific and only work on a small range of substances.

Increasing Reaction Rates

Increasing Reaction Rates

The lock and key model. Substrate attaches to the active site on the enzyme.

Enzyme causes a reaction to occur.

Increasing Reaction Rates

Increasing surface area Allows for more collisions between particles.

Stirring is a way of increasing the surface area.

Increasing Reaction Rates

Image Credits

‘States of Matter’ by Wendy Adams et al available at https://phet.colorado.edu/en/simulation/states-of-matter courtesy of PhET Interactive Simulations at the University of Colorado.

‘Induced Fit Diagram’ By Created by TimVickers, vectorized by Fvasconcellos (Provided by TimVickers) available at http://upload.wikimedia.org/wikipedia/commons/2/24/Induced_fit_diagram.svg, via Wikimedia Commons