Chemical Reactions Flashcards
What indicates a chemical reaction?
A colour change, a flame or explosion, a reaction that gets hot or cold by itself, a gas is produced without heating, and a solid is produced without cooling.
What happens to bonds during a chemical reaction?
Some bonds are broken and others form to make new chemicals.
What remains constant in a chemical reaction?
The chemical formulae (the ‘small’ numbers) cannot change; there are the same number of atoms of each element in the reactants and products.
What is the significance of the number of atoms in reactants and products?
If there are 2 oxygen atoms in the reactants, there must be 2 in the products.
What symbol is used instead of an equals symbol in chemical equations?
An arrow is used.
What occurs during an increase in temperature in a reaction?
Energy is transferred to the thermal store or the surroundings.
What occurs during a decrease in temperature in a reaction?
Energy is transferred from the thermal store of the surroundings.
What is oxidation?
When an element combines with oxygen to form a compound.
What is an example of oxidation?
A fuel rapidly reacts with oxygen transferring energy to the thermal store of the surroundings.
What is thermal decomposition?
A compound is broken down by heat.
How do you test for carbon dioxide?
Bubble through limewater; the limewater turns cloudy.
What happens when a more reactive metal takes the place of a less reactive metal in a compound?
A reaction occurs.
Why are alkali metals reactive?
They have 1 electron in their outer shell.
Why are halogens reactive?
They have 7 electrons in their outer shell.
Why are noble gases not reactive?
They have a full outer shell.
What happens when hydrogen ions from an acid combine with hydroxide ions from an alkali?
They form water.
What is produced from an alkali reacting with an acid?
Salt + water.
What is produced from a carbonate reacting with an acid?
Salt + water + carbon dioxide.
What is a catalyst?
A chemical that speeds up a chemical reaction without being used up in the reaction.
What do catalysts do to the energy barrier of a reaction?
They reduce the energy barrier which increases the rate of reaction.
What are some examples of elements that can be involved in reactions?
Oxygen, Nitrogen, Hydrogen, any halogen (group 7 element).
