Science- Chemical Reactions Flashcards
List 5 key signs of a chemical reaction
A colour change.
A flame or explosion.
Reaction gets hot or cold by itself.
A gas is produced in the reaction without heating.
A solid is produced in the reaction without cooling.
What happens in a chemical reaction?
Some bonds are broken and others form to make new chemicals.
What does not happen in a physical change?
No bonds are broken or formed.
When balancing a chemical reaction, what must we not change?
The chemical formulae i.e. the “small” numbers cannot change.
What do we mean by a balanced chemical reaction?
There are the same number of atoms of each element in the reactants and in the products.
“What is wrong with this balanced equation?
2Ca + O2 = 2CaO”
An = symbol is used instead of an arrow (the 2 in O2 should also be a subscript)
How do you identify an exothermic reaction?
An increase in temperature as energy is transferred to the thermal store of the surroundings.
How do you identify an endothermic reaction?
A decrease in temperature as 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 combustion?
When a fuel rapidly reacts with oxygen transferring energy to the thermal store of the surroundings (high temperature).
Rusting would be an example of what type of chemical reaction?
Oxidation.
Are metal oxides acidic or alkaline?
Alkaline e.g. sodium hydroxide is a drain cleaner.
Are non-metal oxides acidic or alkaline?
Acidic.
What happens when a compound combusts?
Each element in the compound forms an oxide.
Methane is a hydrocarbon (it contains carbon and hydrogen), what products form when it combusts
Water (oxidation of hydrogen) and carbon dioxide (oxidation of carbon).
