GCSE Chemistry (AQA)
196 videos | 19 hours
Enable autoplay to keep watching
Your browser is blocking videos from playing automatically. To turn it back on:
Safari (Mac): Click the Safari menu item in the top bar, then Settings → Websites → Auto-Play, then set Auto-Play to Allow All Auto-Play for the current website.
Safari (iPhone/iPad): open the Settings app, then Apps → Safari → Auto-Play, and select Allow All Auto-Play.
Chemical Equations
- In chemical reactions, substances that react together are called reactants.
- Example: Magnesium and sulfuric acid are reactants.
- Products are substances produced after reactants react.
- Example: Magnesium and sulfuric acid produce magnesium sulfate and hydrogen gas.
- Chemical reactions can be represented by word equations.
- Example word equation: Magnesium + sulfuric acid ��� magnesium sulfate + hydrogen.
- Reactants are on the left of the arrow, products on the right.
- The arrow shows the direction of the reaction.
- Plus signs indicate reactants reacting together or multiple products.
- Understanding word equations is important for exams.
- Chemical reactions can also be written as symbol equations.
- Symbol equations use chemical formulas for reactants and products.
- Example: Magnesium (Mg) and sulfur (S) react to form magnesium sulfide (MgS).
- Numbers in symbol equations multiply the atoms or molecules that follow.
- Example: 2 H��� + O��� ��� 2 H���O indicates two hydrogen molecules and two water molecules.
- Subscripts indicate the number of atoms in a molecule.
- Multipliers apply to the entire molecule; subscripts apply to the symbol they follow.
- Numbers in symbol equations are read with the formula, e.g., "two H��� reacts with O��� to form two H���O."
Please subscribe to access these revision notes.
This, and all other video notes, are included in our premium subscriptions.
Premium accounts get access to all videos and revision notes.
60
questions for Atomic structure and the periodic table
52
questions for A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes