Chemical Reactions Flashcards
What is an endothermic reaction
A reaction which overall takes in energy from the surroundings in the form of heat shown by a fall in temperature
Breaking bonds is endothermic
Photosynthesis is endothermic and ammonium nitrate dissolving in water is also
What is a np exothermic reaction
An exothermic reaction is one which overall gives out energy to the surroundings in the form of heat shown by a rise in temperature
Forming bonds is exothermic
Combustion and explosions are both exothermic
What happens In an exothermic reaction
The products are lower in energy than the reactants the difference in height represents the energy given out in the reaction
What happens in an endothermic reaction
The products are higher in energy than the reactants the difference in height represents the energy take in in the reaction
How can you measure temperature change in a reaction
Take the temperature of the reactants mix them in a polystyrene cup and measure the temperature at the end of the reaction
They should be in a polystyrene cup in a beaker of cotton wool to give more insulation and put a lid on the cup to reduce the energy lost by evaporation
What does the rate of reaction depend on
Temperature
Concentration/pressure
Catalyst
Surface area of solid/size of particles
How does increasing surface are effect the rate of reaction
It means there’s more space for collisions to happen and the rate of reaction is faster and more successful collisions and the reaction is over quicker
How does concentration effect the rate of reaction
There are more particles of the reactant compared to water molecules so collisions are more likely to happen if you increase the pressure then the particles are more squashed so it has the same effect
How does higher temperature effect the rate of reaction
When the temp is increased the particles all move quicker so there will be more frequent collisions and the rate of reaction increases
How do catalysts increase the rate of reaction
It gives the particles a surface to stick to so increase the number of C Lois’s ions by reducing the amount of energy the particles need to collide with each other
What Is a catalyst
A substance which changes the speed of the reaction without being used up in the reaction
They lower the energy needed for the reactants to react
What are catalytic converters
They’re found in motor vehicles they increase the rate that carbon monoxide and unburned fuel in the exhaust react with oxygen in the air to produce carbon dioxide and water
It has a large surface area and high temperature
How do you creat faster collisions
By increasing the temperature it gives the particles more energy to collide
