Chemistry Fundamentals
Chemistry in prelims is mostly named substances and their common uses, plus the periodic table's logic. The single highest-yield habit is knowing the everyday name, chemical name and formula of the common household compounds.
Mental model
Hang chemistry on the periodic table as a map, not a list: left = metals that LOSE electrons, right = non-metals that GAIN them, far right = noble gases that do neither. Reactivity rises down group 1 and rises up group 17. Every acid-base, corrosion and displacement question is just electrons moving from the left of the table to the right.
Associations
A short trigger on the left, everything it pulls with it on the right.
Three names for one thing: common, chemical, formula.
Baking soda is sodium bicarbonate; washing soda is sodium carbonate; plaster of Paris comes from gypsum; quicklime is calcium oxide and slaked lime calcium hydroxide. Questions give you one of the three names and ask for another, so learn all three together.
Alloys are recipes: brass, bronze, steel.
Brass is copper and zinc; bronze is copper and tin; stainless steel is iron with chromium and nickel. Three recipes, and questions ask them as often as they ask anything else in inorganic chemistry.
Things to remember
The night-before list. Short enough to recall cold.
- 1The modern periodic table arranges elements by increasing atomic number, following Moseley's correction to Mendeleev's arrangement by atomic mass.
- 2pH below 7 is acidic, exactly 7 neutral and above 7 basic; the scale is logarithmic, so each unit is a tenfold change.
- 3Diamond and graphite are allotropes of carbon: diamond is the hardest natural substance, graphite conducts electricity because of free electrons.
- 4Rusting of iron needs both oxygen and moisture; galvanisation coats iron with zinc to prevent it.
- 5A catalyst changes the rate of a reaction without being consumed; the Haber process uses iron as catalyst to make ammonia.
- 6Soap works because one end of the molecule dissolves in water and the other in grease, lifting dirt away.
In detail
- pH scale runs 0-14: below 7 acidic, 7 neutral, above 7 basic. Each unit is a tenfold change in hydrogen ion concentration.
- Air is roughly 78% nitrogen and 21% oxygen by volume; the rest is argon, carbon dioxide and traces.
- Common name to formula pairs worth memorising: baking soda = sodium bicarbonate, washing soda = sodium carbonate, quicklime = calcium oxide, slaked lime = calcium hydroxide, plaster of Paris = calcium sulphate hemihydrate.
- Rusting of iron needs BOTH oxygen and moisture; that is why galvanisation (zinc coating) and painting prevent it.
- The atomic number (number of protons) fixes the element's identity; changing the number of neutrons only gives an isotope.
Where people slip
- Baking soda and washing soda are different compounds with different formulas — a favourite swap.
Check yourself
Nothing here is scored — it will not change your mastery figures.
Brass is an alloy of:
From the question bank
What is the pH value of pure water at room temperature?
From the question bank
Who developed the periodic table of elements arranged by increasing atomic weight?
Books to read
- NCERT Class X — Science
- NCERT Class XI — Chemistry
- Lucent's General Knowledge
Official sources
Hand-checked official domains only — the notes above carry no links of their own.