Math and natural sciences

How to learn chemistry from scratch

Chemistry looks frightening because of all the formulas, but it rests on a handful of ideas — what an atom is made of, why atoms bond, and how to count substances in moles. Take them in order and the rest — organic chemistry, solutions, electrochemistry — builds on a solid base. Below is a three-to-four-month plan for an adult starting from an almost blank page.

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What you need before you start#

From math you need ratios, percentages and the ability to solve a linear equation. If that has faded, spend a week revising: most calculation problems in chemistry are a proportion written in masses and moles, and the same moves as in how to solve linear equations and percentage word problems do the work. Beyond that you need a periodic table — printed or open in a browser tab — a notebook for equations, and one textbook that you will follow from start to finish. Jumping between five sources at the beginning is worse than sticking with one.

Stage 1: the atom and the periodic table#

Spend the first two or three weeks on atomic structure: protons, neutrons, electrons, what the atomic number and the mass number mean, and where isotopes come from. Then learn how the table is organised: why elements in the same group behave alike, and how an element's position tells you its typical valence and whether it tends to give up or take on electrons. A good sign that the stage is done: you can look at the table and say how many protons a sulfur atom has, and why sodium and potassium behave in similar ways.

Stage 2: chemical bonds and formulas#

Ionic, covalent and metallic bonding explain why table salt is a solid that dissolves in water while methane is a gas. At this stage, learn to write formulas from charges and valence and to name compounds: oxides, acids, bases, salts. Do not memorise names as a list — derive them from the naming rules, and a new compound will no longer cause panic.

Stage 3: the mole, equations and calculations#

The mole is the key idea for problems. You take the molar mass from the table, and after that almost any problem is solved with one chain: mass → amount in moles → ratio from the equation → mass of the other substance. First learn to balance equations, then solve problems on the mass of a product, on limiting and excess reactants, and on concentration of a solution. Write the units on every line: that alone catches half of all mistakes.

Stage 4: types of reactions and first steps in organic chemistry#

Precipitation, acid–base and redox reactions, single replacement and electrolysis — here a solubility table and the activity series of metals help a lot. After that you can move on to organic chemistry: hydrocarbons, functional groups, isomers. Organic chemistry is a language of its own, and it is worth learning like a language: one class of compounds at a time, with the structures drawn by your own hand.

How to keep chemistry notes#

Set aside separate pages for three things: definitions in your own words, typical problems with a worked solution, and "traps" — the places where you made a mistake. For reactions a table works well: reactants, products, conditions, the visible sign (a precipitate, a gas, a colour change). Formulas are worth moving into flashcards and reviewing at growing intervals with spaced repetition.

Common mistakes#

  • Memorising reactions without understanding why they happen. It is better to work out what exactly gives up and what takes on electrons.
  • Skipping calculations with "I'll get to it later". Without the mole, chemistry stays a collection of pictures.
  • Watching videos without solving anything. Understanding is checked only by a problem you solved with no hints — the principle behind active recall.
  • Repeating experiments from online videos at home. Many reactions are dangerous; virtual labs and recorded demonstrations are enough to see what happens.

Step-by-step plan

  1. Weeks 1–3 — the atom and the tableProtons, neutrons, electrons, isotopes; groups and periods, valence from an element's position.
  2. Weeks 4–6 — bonds and namingTypes of chemical bond, writing formulas, the main classes of inorganic compounds.
  3. Weeks 7–10 — the mole and calculationsBalancing equations, problems on product mass, limiting reactants and concentration.
  4. Weeks 11–14 — reactions and organic chemistryReaction types, the activity series, solubility; then hydrocarbons and functional groups.

Start learning this in your own space

The plan goes into your repository: tick off stages, keep notes — the change history shows how far you have come.

Start the plan

Check yourself

1.What is the molar mass of water, H2O, in g/mol, if the atomic masses are H = 1 and O = 16?

2.How many protons are in the nucleus of a carbon atom (atomic number 6)?

3.What is the molar mass of CO2 in g/mol, if the atomic masses are C = 12 and O = 16?

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