⚗️ What is a word equation?
It’s a plain‑English description of a chemical reaction.
Example: “Hydrogen gas reacts with oxygen gas to form water.”
🔬 What is a symbol equation?
It’s the same reaction written with chemical symbols and state symbols:
\$\ce{H2(g) + O2(g) -> H2O(l)}\$
State symbols tell you whether a substance is a solid (s), liquid (l), gas (g) or aqueous (aq).
They help you check if the reaction is physically possible and are required for exam answers.
Write them in plain English first.
Use the periodic table.
Think of the temperature and pressure conditions (room temperature, 1 atm).
Make sure the same number of each atom appears on both sides.
Verify that the equation is balanced and that state symbols are correct.
Imagine each atom is a Lego brick.
To build a product, you must use the exact number of bricks (atoms) from the reactants.
If you have too many or too few bricks, the structure won’t hold – just like an unbalanced equation.
| Step | Description |
|---|---|
| Word Equation | Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor. |
| Symbol Equation (unbalanced) | \$\ce{CH4(g) + O2(g) -> CO2(g) + H2O(g)}\$ |
| Balanced Symbol Equation | \$\ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g)}\$ |
✨ Tip: Always write the state symbols in parentheses immediately after each chemical formula.
📝 Remember: The balanced equation must have the same number of atoms of each element on both sides.
💡 Check your answer: Count the atoms again; if they match, you’re good to go!
Answer:
Word: “Sodium metal reacts with chlorine gas to produce sodium chloride solid.”
Symbol: \$\ce{Na(s) + Cl2(g) -> NaCl(s)}\$
Balanced: \$\ce{2Na(s) + Cl2(g) -> 2NaCl(s)}\$