Chemistry 1 (Grade 10)

Matter and its properties, atomic structure and radioactivity, chemical reactions, and the mole.

Units of the book

Unit	What to know
Introduction	scientific methods, mass and weight
Matter	physical vs chemical, mixtures and separation, elements and compounds, conservation of mass
The atom	Dalton, Thomson, Rutherford, protons, neutrons, electrons, isotopes, radioactivity
Chemical reactions	equations, reaction types, reactions in solution
The mole	Avogadro’s number, molar mass, conversions, percent composition

Formula	In plain words	How to remember it
Z = p⁺, A = p⁺ + n⁰	Atomic number = protons; mass number = protons + neutrons.	Z is the element’s identity; A is its weight.
n⁰ = A − Z	Number of neutrons.	Mass number minus atomic number.
e⁻ = Z − الشحنة	Electrons in an ion.	A positive ion lost electrons (Na⁺: 10); a negative ion gained (Cl⁻: 18).
الكتلة الذرية = Σ(الكتلة × النسبة)	Average atomic mass of the isotopes.	The answer lands nearest the most common isotope.
n = m / M	Moles = mass ÷ molar mass.	M is in g/mol, so the grams cancel and moles remain.
N = n × 6.02 × 10²³	Particles = moles × Avogadro’s number.	A mole is a giant “dozen”: 6.02 × 10²³.
% = (كتلة العنصر / كتلة المركب) × 100	Percent by mass of an element in a compound.	“Part ÷ whole × 100.”
ألفا: A − 4, Z − 2 \| بيتا: Z + 1	Decay: alpha loses a helium nucleus; beta turns a neutron into a proton.	Alpha = ⁴₂He so take away 4 and 2. Beta leaves A unchanged.
كتلة المتفاعلات = كتلة النواتج	Conservation of mass (Lavoisier).	Nothing disappears in a reaction; that is why we balance equations.

Topic	What to know
Dalton	atoms are solid spheres that cannot be divided; atoms of one element are identical.
Thomson	discovered the electron with cathode rays; the “plum pudding” model.
Rutherford	the gold-foil experiment: discovered the nucleus; the atom is mostly empty space.
Chadwick	discovered the neutron.
Millikan	measured the electron’s charge with the oil-drop experiment.
Isotopes	atoms of one element with different numbers of neutrons (same Z, different A).
Signs of a chemical change	gas bubbles, a new colour, a precipitate, heat or light given out, a new smell. Melting, boiling, dissolving and grinding are physical changes.
Separating mixtures	filtration → a solid from a liquid (particle size). Distillation → two liquids (boiling point). Crystallization → a dissolved solid. Chromatography → ink colours (how fast they move). Magnet → iron. Sublimation → iodine, naphthalene.
Homogeneous vs heterogeneous	homogeneous (a solution) is the same throughout: salt water, air, an alloy. Heterogeneous shows its parts: sand and water, a salad.
Types of reactions	synthesis A + B → AB, decomposition AB → A + B, single replacement A + BC → AC + B, double replacement AB + CD → AD + CB, combustion: fuel + O₂ → CO₂ + H₂O.
Double replacement happens if	a precipitate, a gas or water forms.

Empirical formula in four steps: “percent to mass, mass to mole, divide by the smallest, multiply till whole”.
Atom discoveries in order: Dalton (sphere), Thomson (electron), Rutherford (nucleus), Bohr (levels).
Cations are positive: the “t” in cation looks like a + sign.

Understand before you memorize: read “in plain words” for each formula and say out loud what it measures and why each quantity is multiplied or divided. A formula you understand takes a minute to learn.
Active recall: cover the formula column and write it from memory, then check. Writing from memory beats rereading by far.
Spaced repetition: review the same sheet after 1 day, 3 days, a week and two weeks. Four short reviews lock it in until test day.
Your own formula page: write every formula of a book on one page by hand. If it does not fit, you are writing things you can derive, so cut them.
Teach it: explain the formula to a friend, or to yourself in a mirror, in two sentences. If you cannot explain it, you do not know it yet.
Use it at once: after each group, press “Try one” in the patterns below. Memory sets when you use it.

A new substance (colour, gas, heat, smell) → chemical. Only shape or state → physical.

Filtration for insoluble solids; distillation for different boiling points; chromatography for different speeds.

Atomic number = protons. A positive ion lost electrons; a negative ion gained them.

Each half-life halves the amount.

Synthesis, decomposition, single replacement, double replacement, combustion (with O₂).

Mass ÷ molar mass = moles; moles × 6.02×10²³ = particles.

(mass of the element in one mole ÷ molar mass) × 100.