Topic 7 Groups, Rate And Energy Flashcards
(25 cards)
What must happen for a chemical reaction to happen
Particles must collide with enough energy
What is the activation energy
Minimum energy with which particles must collide in order to cause a chemical reaction
How can we increase the rate of reaction
Increasingthe frequency of successful collisions
What are the main factors affecting reaction rates
Temperate
Concentration
Pressure (for gasses)
Surface area
What are substances that increase a chemical reactions rate
Catalysts
How do catalysts increase rate of reaction
They lower the activation energy and they do this by changing the reaction pathway
What are examples of catalysts
Iron - used in process that makes ammonia
Enzymes catalyse reactions in biological systems
Why are faster reactions often better
They yield more product in a given time
What is the test for measuring gas production ( rate of reaction)
Make sure measuring cyclinder is full with water
Place in a known mass of marble chips
Pour in a known concentration and excess volume of acid.
What is the independant variable in the test for gas
The surface area of marble chips
What is the dependant variable in the gas test
Volume of gas produced every 5 seconds
What are some drawbacks of fast chemical reactions
Safety concerns and cost
When do energy changes happen
When chemical reactions take place
When do changes in heat energy happen
Neutralisation reaction
Precipitation reactions
Salt dissolving in water
Displacement reaction
What is a neutralisation reaction
The reaction between an acid and a base
What is a precipitation reaction
When two solutions react to make an insoluble salt
What happens when salt dissolves in water
Ionic bonds in a salt break so the ions become more mobile in solution
What is a displacement reaction
When a more reactive metal takes the place of a less reactive metal.
What is an exothermic reaction
Where energy from the reacting chemicals is transferred to the surroundings which often leads to an increase in temperature
What are some examples of exothermic reactions
Hand warmers
Oxidation
Combustion
Neutralisation
What is an endothermic reaction
Energy from the surroundings is transferred to the reacting chemicals which decreases the temperature
What are examples of endothermic reactions
Citric acid + baking soda
Thermal decomposition
Sports injurt pack
What kind of reaction is bond making
Exothermic
What kind of reaction is bond breaking
Endothermic
