C 1.3 Chemical reactions Flashcards
(12 cards)
What is a chemical reaction?
A process where new substances are formed with different properties from the original substances.
What happens to atoms during a chemical reaction?
Atoms are rearranged; they are not created or destroyed.
What is the law of conservation of mass?
Mass is conserved in a chemical reaction — the total mass of the products equals the total mass of the reactants.
What is a word equation?
A way of showing a chemical reaction using the names of substances (e.g. hydrogen + oxygen → water).
What is a symbol equation?
A chemical equation that uses chemical symbols and formulas to represent reactants and products (e.g. 2H₂ + O₂ → 2H₂O).
Why must symbol equations be balanced?
To show that the same number of each type of atom is present on both sides of the equation.
What is a reactant?
A substance that takes part in and is changed during a chemical reaction.
What is a product?
A new substance formed as a result of a chemical reaction.
What is an ionic equation?
An equation that shows only the particles involved in the reaction, often used for reactions in solutions.
What is a state symbol, and what are the common ones?
State symbols show the physical state of substances:
(s) = solid
(l) = liquid
(g) = gas
(aq) = aqueous (dissolved in water)
What are signs of a chemical reaction?
Colour change
Gas production (bubbles)
Temperature change
Formation of a solid (precipitate)
How can you prove a gas is formed in a reaction?
By collecting it and testing it, e.g.:
Hydrogen → ‘pop’ with a lit splint
Oxygen → relights a glowing splint
Carbon dioxide → turns limewater cloudy
