Chemistry has its own written language: symbols for elements, formulae for compounds, and balanced equations for reactions.
Every element has a symbol of one or two letters, the first a capital and the second lower case. Getting that wrong changes the substance entirely: CO is carbon monoxide, Co is cobalt.
A formula shows the atoms in a compound and how many of each. In H2SO4 there are two hydrogen atoms, one sulfur and four oxygen. A number in front multiplies the whole formula: 2H2O means two water molecules, so four hydrogen atoms and two oxygen.
Atoms are only rearranged in a reaction, so the total mass of the products equals the total mass of the reactants.
That is the reason equations have to balance, and the reason an apparent gain or loss of mass in these reactions usually means a gas has been taken in or given off.
Bonds in the reactants break and new bonds form in the products. The atoms present at the start are exactly the atoms present at the end, joined up differently.
Start with a word equation, then replace the names with formulae. Count each kind of atom on both sides, and put whole numbers in front of formulae until the counts match.
Never change a subscript inside a formula to make it balance: H2O is water but H2O2 is hydrogen peroxide, a different substance. State symbols may be added: (s) solid, (l) liquid, (g) gas, (aq) dissolved in water.
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