Starter quiz
- What is a chemical reaction?
- A process where substances are mixed but not changed.
- A process where substances change into new substances. ✓
- A process where substances retain their original properties.
-
- What are reactants?
- Substances that are formed as the result of a chemical reaction.
- Substances that do not change during a reaction.
- Substances that take part in and undergo change during a reaction. ✓
-
- What are products?
- Substances that are formed as the result of a chemical reaction. ✓
- Substances that are mixed but not changed.
- Substances that take part in and undergo change during a reaction.
-
- What is a word equation?
- A representation of a chemical reaction using numbers.
- A representation of a chemical reaction using symbols.
- A representation of a chemical reaction using names of the chemicals involved. ✓
-
- What does the conservation of mass mean?
- Mass is always decreased in a chemical reaction.
- Mass is always increased in a chemical reaction.
- Mass is neither created nor destroyed in a chemical reaction. ✓
-
- What is a chemical symbol?
- A number representing the mass of an element.
- A one- or two-letter representation of an element. ✓
- A phrase describing an element.
-
Exit quiz
- What does a half-equation describe?
- What happens to all reactants in a reaction.
- What happens to one reactant in a reaction. ✓
- What happens to the products in a reaction.
-
- What do half-equations show?
- Only the atoms
- Only the charges
- Balanced charges and balanced atoms ✓
-
- When an atom gains electrons we say it has been ...
- thermally decomposed.
- oxidised.
- reduced. ✓
-
- In an electrolysis cell, where does oxidation occur? why?
- At the cathode, because positive ions gain electrons.
- At the anode, because negative ions lose electrons. ✓
- At the cathode, because negative ions lose electrons.
- At the anode, because positive ions gain electrons.
-
- What are spectator ions?
- Ions that are formed as a result of the reaction.
- Ions that do not take part in the reaction. ✓
- Ions that react during the reaction.
-
- In the electrolysis of molten zinc chloride, the ionic equation is Zn²⁺(l) + 2Cl⁻(l) → Zn(s) + Cl₂(g). Which of the following is correct?
- H⁺ and OH⁻ are spectator ions.
- Zn²⁺ is a spectator ion.
- There are no spectator ions. ✓
-
Worksheet
Presentation
Video
Lesson Details
Key learning points
- A half–equation describes what happens to one reactant in a reaction, such as the process at an individual electrode.
- Half–equations show balanced charges as well as balanced atoms.
- A balanced ionic equation shows all reacting ions involved in a reaction.
- Ions not involved in a reaction do not appear in a balanced ionic equation.
Common misconception
Getting the electrons confused; how many and which side of the half equations to write them on.
When writing a half equation, electrons should be added and not taken away and so should go on the side of the equation where they are added. All charges must cancel each other out and the atoms on each side of the equation balance.
Keywords
Reduction - a type of reaction in which a substance gains electrons or loses oxygen
Oxidation - a type of reaction in which a substance loses electrons or gains oxygen
Half–equation - a chemical equation used to show the electrons lost in oxidation or the electrons gained in reduction
Ionic equation - a balanced equation showing all the ions involved in a reaction
Spectator ions - the ions not involved in a chemical reaction