Chemical Reactions- Physical and chemical changes + Rates of reactions Flashcards
What do physical changes not produce?
New chemical substances
What is it easy to do with physical changes?
Easy to reverse
Give examples of physical changes.
Evaporating
Melting
What do chemical changes produce?
New chemical products that have very different properties to the reactants. These reactions are impossible to reverse.
What are most chemical reactions?
Exothermic
How can you increase the rate of reaction?
Increasing the temperature Increasing the surface area Increasing the concentration Increasing the pressure Adding a catalyst
How does increasing the temperature increase the rate of reaction?
Particles have more energy so hit each other more often and more of the collisions have enough energy to react
Increase in collision rate+ energy
How does increasing the surface area increase the rate of reaction?
There are more particles of the solid able to collide with particles of a liquid
How does increasing the concentration increase the rate of reaction?
The particles are closer together so are more likely to collide
Increases collision rate ONLY
How does increasing the pressure increase the rate of reaction?
The particles are closer together so are more likely to collide
How does adding a catalyst increase the rate of reaction?
A catalyst reduces the activation energy needed and particles need less energy to collide with each other
How can you measure the rate of reaction?
Measuring the rate at which reactants are used up
Measuring the rate at which products are made
Why do explosive combustions happen in wind mills?
There are fine particles in the air and these have a large SA and are combustible in air because the rate of reaction is fast
How can you investigate the rate of reaction? -3
Measuring the loss in mass when a gas is made
Measuring the volume of gas given off
Measuring the length of time for a precipitate to be made
What is a catalyst?
A substance that speeds up the rate of reaction without being used up
