What is a catalyst? Explain how a catalyst will speed up a chemical reaction:
a chemical that lowers the activation energy of a reaction.
Use collision theory to explain why reactions should occur more slowly at lower temperatures
They need enough energy in order for a chemical reaction to occur. Lowering the temperature will cause the molecules to react slowly. Instead, they are more spread out instead of close together.
Explain how grinding up a solid into smaller pieces can speed up the reaction. Use collision theory in your answer
The particles in the crushed chalk are spread out creating more surface area. This comes into contact with whatever variable you are using to increase the chances of successful collisions.
Explain why all reactions have an activation energy, using your knowledge of collision theory:
Activation energy is the amount of energy required for a chemical reaction to begin. Particles and molecules need enough energy and orientation in order to create a chemical reaction. They both need energy in order to create a chemical reaction.
Describe the effect of increasing the concentration of the reactants on the rate of a reaction.
Increasing the concentration of a reactant simply means there are more particles which may collide and so react. More collisions means a faster reaction.
When a beaker of water is heated its volume increases a little. What is happening to the particles in the liquid?
They are moving faster.
A substance consisting of two elements physically combined is known as a(n)
A mixture of sand and iron particles can be separated by
Which of the following cannot be broken down into simpler substances by mechanical or physical means?
Which of the substances below is NOT a compound?
The smallest particle of an element to still retain all of the properties of the element is the
At its deposition point, matter changes from a
gas to solid
Molecules in gas are arranged as follows
very spaced out and free to move from one end to another
Which of the following signs does NOT indicate that a chemical change has happened?
How does the density of a pure gold bar compare to a pure gold bracelet?
it is the same
Which of the following involves a CHEMICAL CHANGE?
paper turns into ash
the smallest particle that represents an element that retains all of the same properties of that element.
contains only one kind of matter (can be an atom, molecule or compound, as long as it is the only type of atom, molecule or compound in the sample) Pure Substances will have a chemical symbol (elements) or formula (molecules and compounds)