Post on 31-Mar-2015
NATIONAL 4/5 CHEMISTRY
CHEMICAL CHANGES AND STRUCTURE
LESSON 1
REVISION OF FACTORS THAT SPEED UP A REACTION
A working knowledge of the factors affecting rates of reaction is required for this Course. To compare rates of chemical reactions, changes in mass, volume and other quantities can be measured. Graphs can then be drawn to help this comparison.
National 4 Chemistry:
Rates of reaction Reactions monitored and graphs interpreted
Previous Learning from S3:Through experimentation, I can identify indicators of chemical reactions having occurred. I can describe ways of controlling the rate of reactions and can relate my findings to the world around me. SCN 3-19a
Describe how the following affect the speed of a reaction:
• particle size• concentration• Temperature• State that catalysts are
substances which: speed up some reactions are not used up during the reaction can be recovered chemically unchanged
Important Point to note: in order for chemists to monitor the rate of
a reaction we must observe a CHANGE in response to a chemical
change occurring. Reactants changing to products
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Contents
Effect of surface area
Rates of reactionsThe speed of different chemical reactions varies hugely. Some reactions are very fast and others are very slow.
fast
very fast
very slow
fast
slow
Burning magnesium
fireworks
chemical weathering of rocks
sodium and water
rotting fruit
Reaction Rate
What is the rate of these reactions?
The speed of a reaction is called the rate of the reaction.
Reactions occur when particles of reactants collide with enough energy to react (activation energy).
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Effect of surface area
Contents
Temperature and rate of reaction video
WATCH THE VIDEO TEMPERATURE AND RATE OF REACTION VIDEO!
The effect of temperature on collisionsHow does temperature affect the rate of particle collision?
Temperature and particle collisions
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Effect of surface area
Contents
Concentration and reaction rate video
3% hydrogen peroxide solution
30% hydrogen peroxide solution
Add more solute (hydrogen peroxide) to the same volume
WATCH THE CONCENTRATION AND REACTION RATE VIDEO!
Increasing concentration
Concentration
Reactions in solution involve dissolved particles. The more crowded (concentrated) the solution, the faster the reaction.
Higher concentration more particles more collisions faster reaction
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Effect of surface area
Contents
Surface area and reaction rate video
WATCH THE SURFACE AREA AND REACTION RATE VIDEO !
Surface area
Molecules collide with the surface of the solid
Extra surface for molecules to collide with.
Reactions of solids can only take place at the surface of the solid. If we break a solid into smaller pieces we get a larger surface area and a faster reaction.
Smaller particles larger surface area more collisions faster reaction
• If we grind up a solid to a powder we massively increase the surface area.• We therefore massively increase the rate of any reaction
Very fast
Slow
Surface area
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Effect of surface area
Contents
Enzymes – biological catalyst
Watch the catalyst video!
Rates of Reaction
Effect of concentration
Effect of catalysts
Introduction
Summary activities
Effect of temperature
Effect of surface area
Contents
Glossaryactivation energy – The amount of energy needed for a
reaction to begin.
adsorption – The formation of a layer of molecules on the surface of a solid.
catalyst – A substance that changes the rate of a reaction without being used up.
concentration – The amount of particles in a given volume.
enzyme – A biological catalyst.
rate of reaction – The speed with which a particular chemical reaction progresses.
Particles and rates of reaction
Anagrams
Stages of a reaction
Multiple-choice quiz