C2.5 Chemical reactions Flashcards
What types of chemical reaction include a temperature change?
- dissolving
- neutralisation
- displacement
- precipitation
What is neutralisation?
When an acid reacts with a base
Are all combustion reactions exothermic or endothermic?
Exothermic
What are explosions?
Exothermic reactions that release a lot of heat energy and gases very quickly
What happens during an endothermic reaction?
They take in heat energy from surroundings so the temperature decreases
What are three examples of endothermic reactions?
- ammonium nitrate in water
- sodium hydrogen carbonate with hydrochloric acid
- photosynthesis
Why is breaking bonds an endothermic process?
Because it takes energy to break bonds which is taken from surroundings
Why is making bonds an exothermic process?
Because energy is released when bonds are made
Why is heat released in an exothermic reaction?
Less energy is needed to break the bonds in the reactants than it does to make the new bonds in the products, so heat energy is released
Why is heat absorbed in an endothermic reaction?
More energy is needed to break the bonds of the reactants than it does to form new bonds between the products, so energy is absorbed
What do energy diagrams show?
Changes during reactions
Is rain naturally acidic or alkaline?
Acidic
What is limestone made out of?
Calcium carbonate
What are three things that affect the rate of a chemical reaction?
- temperature
- surface area of the solid
- concentration of the solutions
What is the rate of a chemical reaction?
The speed at which it takes place
What happens to the rate of reaction when you cool a reaction?
It slows down
What is the concentration of a solution?
The measure of how much solute is dissolved in the solvent
What must happen for a reaction to occur?
Particles of the reacting substances must collide with each other
What must particles do to increase the rate of reaction?
- collide more frequently
- collide with a greater force
How can you increase the rate of reaction?
- increase in temperature
- increase in concentration
- increase in surface area
Why is increasing concentration effective in increasing the rate of reaction?
There are more solute particles in a given volume which means it is more likely the reactant particles will collide with one another
Why does increasing temperature increase the rate of reaction?
Particles move faster which means there are more collisions and that when particles do collide they collide with more force which means they are more likely to react
Why does surface area increase the rate of reaction?
Only the surface particles can be involved in a reaction in a solid, so the greater the surface area, the more particles there are that can collide
What are catalysts?
Substances that speed up chemical reactions without being used up themselves
Why are catalysts used?
To increase the rate of production of products
What are three examples of a catalyst?
Iron, nickel and aluminium oxide
How do catalysts save money and energy resources?
Reactions can be done at lower temperatures and pressures than they would be at usually, which means less energy is used
What does the combustion of petrol in car engines produce?
Carbon monoxide and unburned hydrocarbons
What do catalytic converters do?
They reduce the pollutants in exhaust gases by combining carbon monoxide and unburned petrol with oxygen from the air to produce carbon dioxide and water vapour
How do catalytic converters work?
They use transition metals like platinum, rhodium and palladium to help speed up the reactions that remove pollutants in exhaust gases
How are catalytic converters made as efficient as possible?
The catalyst has a fine honeycomb structure to increase surface area
How is the amount of catalyst used in a catalytic converter minimised?
It is applied in a very thin surface coat
