Basic Concepts, Matter & Measurement

Matter and the changes it undergoes. Matter is anything that has mass and occupies space.

Alchemy — attempts to turn cheap metals into gold.

Antoine Lavoisier. He named oxygen and hydrogen, explained combustion and proved the Law of Conservation of Mass.

John Dalton, 1808 — matter is made of indivisible atoms.

Chemistry is the branch of science that studies matter and the changes it undergoes.

Matter is anything that has mass and occupies space (air, water, your body).

Antoine Lavoisier

• Antoine Lavoisier is called the Father of Modern Chemistry; he named oxygen and hydrogen.
• Lavoisier proved the Law of Conservation of Mass – matter is neither created nor destroyed in a reaction.

John Dalton

• John Dalton proposed the first scientific Atomic Theory (1808) – matter is made of indivisible atoms.
• John Dalton (1808) gave the first scientific atomic theory and is called the father of modern atomic theory.
• Note: Dalton's theory did NOT explain the law of radioactivity (a common exam trap).
• Dalton's Law: total pressure of a gas mixture equals the sum of partial pressures.

Lavoisier: Father of Modern Chemistry, conservation of mass. Dalton: Atomic Theory (1808). Rutherford: discovered the nucleus. Raman: the Raman effect — he was a physicist.

No — Einstein was a physicist (E = mc²). A common exam trap in 'Father of Chemistry' questions.

Known For

Father of Modern Chemistry; Conservation of Mass

Known For

Atomic Theory (1808)

Known For

Discovered the nucleus

Known For

Raman effect (physicist)

Ernest Rutherford

• Rutherford discovered the atom's nucleus.
• E. Goldstein (1886) found positive 'canal rays'; the proton was later established by Rutherford.
• Based on the famous gold-foil (alpha-particle scattering) experiment (1911).
• Given by Niels Bohr in 1913 to fix Rutherford's stability problem.
• Ernest Rutherford identified alpha and beta rays and proved alpha is a helium nucleus.
• Rutherford proved alpha is helium: gaining 2 electrons it became ordinary helium gas.

Albert Einstein

• Einstein was a physicist (E = mc²), not a chemist.
• Bose-Einstein Condensate (BEC) forms near absolute zero, particles act as one.
• E = mc² (Einstein): a tiny loss of mass releases enormous energy.

C. V. Raman

• C. V. Raman was an Indian physicist famous for the Raman effect of light.

Solid: fixed shape, fixed volume (particles only vibrate). Liquid: fixed volume, no fixed shape (particles slide past). Gas: neither fixed — it fills any container.

A super-hot ionised gas — found in the Sun, stars and tube-lights.

A state formed near absolute zero in which particles act as one.

Matter is made of tiny moving particles with empty space between them.

Shape

Fixed

Volume

Fixed

Shape

Not fixed

Volume

Fixed

Shape

Not fixed

Volume

Not fixed

Diluting potassium permanganate again and again still keeps a faint colour.

Salt dissolves in water with little rise in the water level.

Particles are always moving (incense smell, ink spreading). Heat makes particles move faster, so diffusion is quicker when warm.

Strongest in solids, weakest in gases.

Melting: 0°C (273 K). Boiling: 100°C (373 K). Freezing point equals melting point for a pure substance.

The single temperature and pressure at which solid, liquid and gas coexist — for water, about 0.01°C.

Melting point = solid turns to liquid; for ice it is 0°C (273 K).

Boiling point = liquid turns to gas throughout; water boils at 100°C (373 K).

From → To

Solid → Liquid

Water Value

0°C / 273 K

From → To

Liquid → Solid

Water Value

0°C / 273 K

From → To

Liquid → Gas

Water Value

100°C / 373 K

The slow change of a liquid to gas from its surface only, at any temperature — which is why wet clothes dry on a cool day.

The fastest particles escape, leaving the rest cooler — sweating cools the body and water stays cold in an earthen pot.

Heat, wind, larger surface area and dry air (low humidity).

A solid changing directly into gas without becoming liquid.

Camphor, naphthalene, ammonium chloride, iodine and dry ice (solid CO₂). Sublimation separates ammonium chloride from salt, and naphthalene from sand.

Sublimation of ammonium chloride – solid turns directly to vapour and re-solidifies on the funnel

Exo = out: heat is released, surroundings feel warmer. Endo = in: heat is absorbed, surroundings feel cooler.

Strongly exothermic: CaO + H₂O → Ca(OH)₂ gives out much heat.

Diluting concentrated acid is exothermic — a large amount of heat is released at once.

Melting of ice, evaporation, sublimation and dissolving some salts — all absorb heat and give a cooling effect.

Proton: positive, in the nucleus. Neutron: neutral, in the nucleus. Electron: negative, outside the nucleus.

The number of protons equals the number of electrons, so the charges cancel.

An atom is the smallest particle of an element that takes part in a chemical reaction.

Protons carry a positive charge and sit in the central nucleus.

Neutrons have no charge and also sit in the nucleus.

Electrons carry a negative charge and move around the nucleus.

Charge

Positive (+)

Location

Nucleus

Charge

Neutral (0)

Location

Nucleus

Charge

Negative (-)

Location

Outside nucleus

Z = number of protons — it decides which element it is. A = protons + neutrons.

Atoms of the same element with different numbers of neutrons — e.g. carbon-12 and carbon-14.

Cation is positive — it has lost electrons. Anion is negative — it has gained electrons.

isotoPes = Proton same · isobar = mass bar (mass number) same · isotoNes = Neutron same.

Molecule = two or more atoms joined together (O₂, H₂O).

An ion is a charged atom: cation (positive) loses electrons, anion (negative) gains electrons.

Element: one kind of atom (gold, oxygen). Compound: two or more elements chemically combined in a fixed ratio (water, salt). Mixture: substances not chemically combined.

Homogeneous is uniform throughout — salt solution, air. Heterogeneous is non-uniform — sand in water, oil in water.

Pure substances have a fixed composition: elements and compounds.

Example

Gold, Oxygen

Example

Water, Common salt

Example

Salt solution, air

Example

Sand in water, oil in water

The solute is the dissolved substance; the solvent dissolves it. In salt water, salt = solute, water = solvent.

A saturated solution holds the maximum solute possible at that temperature; an unsaturated one can still dissolve more.

Only the concentration drops. The amount/mass of sugar does not change, and in an unsaturated solution the volume stays the same too.

Higher temperature usually lets a solvent dissolve more solute.

The amount of solute per unit volume or unit mass of the solution/solvent. Units: molarity (mol/L solution), molality (mol/kg solvent), mass percent.

(mass of solute ÷ mass of solution) × 100.

Dilute solution has little solute; concentrated solution has much solute.

Adding more solvent makes a solution more dilute (concentration falls).

metre (m), kilogram (kg), second (s) and mole (mol).

K = °C + 273, so 0°C = 273 K. Temperature's SI unit is the kelvin (K).

Mass is the quantity of matter — constant everywhere. Weight is the force of gravity on it — it varies with place.

The SI system gives standard base units used worldwide in science.

Temperature is measured in kelvin (K); 0°C = 273 K and K = °C + 273.

SI Unit

metre

Symbol

m

SI Unit

kilogram

Symbol

kg

SI Unit

second

Symbol

s

SI Unit

kelvin

Symbol

K

SI Unit

mole

Symbol

mol