⭐ Second Year Science – Full Revision Notes (Based on Your Document)

🫁 Smoking and Breathing

Respiration vs Breathing

  • Breathing = physical movement of air in and out of the lungs.

  • Respiration = chemical reaction in cells releasing energy from glucose and oxygen.

  • The document lists this as: “The differences between respiration and breathing”

Inhaled vs Exhaled Air

  • Inhaled air: more oxygen, less carbon dioxide, little water vapour.

  • Exhaled air: less oxygen, more carbon dioxide, more water vapour.

Thorax Structure

  • Includes ribs, intercostal muscles, diaphragm, lungs, trachea, bronchi, bronchioles, alveoli.

Ventilation Mechanism

  • Breathing in: diaphragm contracts + flattens, ribs move up/out → chest volume increases → air drawn in.

  • Breathing out: diaphragm relaxes + domes, ribs move down/in → chest volume decreases → air pushed out.

  • Document: “The mechanism of ventilation, i.e. how we breathe”

Gas Exchange

  • Happens in alveoli.

  • Oxygen diffuses into blood; carbon dioxide diffuses out.

Alveoli Adaptations

  • Large surface area

  • Thin walls

  • Moist lining

  • Rich blood supply

Smoking Effects

  • Tar damages alveoli → emphysema

  • Carbon monoxide reduces oxygen transport

  • Nicotine increases heart rate and addiction

  • Document: “The effects of nicotine, tar and carbon monoxide on the body”

Diseases

  • Bronchitis – inflammation of bronchi

  • Emphysema – alveoli breakdown → reduced gas exchange

⚛ Atoms and Elements

Elements

  • Pure substances made of one type of atom.

  • Document: “What an element is”

Atoms

  • Smallest particles of elements.

  • Contain protons (+), neutrons (0), electrons (–).

Symbols

  • Each element has a chemical symbol (e.g., O, Na, Fe).

Periodic Table

  • Organises elements by atomic number and properties.

Metals vs Non‑metals

  • Metals: conduct electricity, malleable, shiny.

  • Non‑metals: poor conductors, brittle, dull.

⚡ Electricity

Electrical Safety

  • Avoid water, don’t overload sockets, use fuses and circuit breakers.

Component Symbols

  • You must recognise: cell, battery, switch, lamp, resistor, ammeter, voltmeter.

Conductors vs Insulators

  • Conductors: metals

  • Insulators: plastic, rubber

Series vs Parallel Circuits

  • Series: all componets are connected end to end, current is the same throughout

  • Parallel: components connected across the same voltage source; current can vary at different branches

Switches

  • Control current flow; can be placed in different parts of circuits.

🍎 Food and Digestion

Why We Need Food

  • Energy, growth, repair, health.

Balanced Diet Components

  • Carbohydrates

  • Proteins

  • Lipids

  • Water

  • Vitamins

  • Minerals

  • Fibre

  • Document lists these exactly: “carbohydrates, proteins, lipids, water, vitamins, minerals and fibre”

Carbohydrate Types

  • Simple: sugars

  • Complex: starch

Deficiency Diseases

  • Example: scurvy (lack of vitamin C)

Food Tests

  • Benedict’s → sugars

  • Iodine → starch

  • Biuret → protein

  • Emulsion → lipids

Digestion

  • Breaking food into small soluble molecules.

Enzymes

  • Amylase → starch

  • Protease → protein

  • Lipase → fats

Digestive System Anatomy

  • Mouth → oesophagus → stomach → small intestine → large intestine → rectum

Teeth & Saliva

  • Teeth break food mechanically

  • Saliva contains amylase

Peristalsis

  • Muscular contractions pushing food along

  • Fibre helps movement

Organs

  • Stomach: acid + enzymes

  • Pancreas: produces enzymes

  • Intestines: absorb nutrients

🧪 Forming Compounds

Chemical vs Physical Changes

  • Chemical: new substance formed

  • Physical: no new substance

Conservation of Mass

  • Mass stays the same in reactions.

Compounds

  • Formed when elements chemically bond.

Chemical Formulae

  • Show elements and number of atoms (e.g., H₂O, CO₂).

Word Equations

  • Reactants → products

  • Example: magnesium + oxygen → magnesium oxide

Predicting Products

  • Metal + oxygen → oxide

  • Metal + sulphur → sulphide

  • Metal + chlorine → chloride

Mixtures

  • Not chemically bonded; easy to separate.

🌍 Space

Solar System Components

  • Sun, planets, dwarf planets, moons, asteroids, comets.

Milky Way

  • Our galaxy.

Universe

  • All space, matter, and energy.

Planet Order

  • Mercury → Venus → Earth → Mars → Jupiter → Saturn → Uranus → Neptune

Orbits

  • Held by gravity of the Sun.

Day & Night

  • Caused by Earth’s rotation.

Seasons

  • Caused by Earth’s tilt + orbit.

Moon Phases

  • New → crescent → quarter → gibbous → full → back again.

Eclipses

  • Solar: Moon blocks Sun

  • Lunar: Earth blocks Sun from Moon

Satellites

  • Polar: orbit poles

  • Geostationary: stay above same point on Earth

📊 Scientific Skills

Units

  • Must include correct units (case‑sensitive).

  • Example from document: “10 cm = 0.1 m”

Variables

  • Independent: changed

  • Dependent: measured

  • Control: kept the same

Experimental Errors

  • Can cause differences between groups.

Reading Equipment

  • Be precise and accurate.

Tables

  • Headings + units

  • Clear layout

Graphs

  • X‑axis: independent variable

  • Y‑axis: dependent variable

  • Use sensible scale

  • Plot points accurately

  • Line of best fit when appropriate

  • Document: “axis correct way round… scale… line of best fit”