Combined Science Full Study Guide

Biology

Cell Structure

  • Cells are the basic units of life.
  • Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.
  • Plant cells have these plus a rigid cell wall, chloroplasts for photosynthesis, and a large permanent vacuole for storage.
  • Prokaryotic cells (like bacteria) are simpler and lack a nucleus.

Cell Division

  • Cells divide for growth and repair through mitosis, producing two identical daughter cells.
  • The cell cycle involves growth, DNA replication, and division.
  • Stem cells are unspecialised cells that can develop into any type of cell, useful in medicine but sometimes ethically debated.

Transport in Cells

  • Substances move in and out of cells by:
    • Diffusion (high to low concentration).
    • Osmosis (water movement through a membrane).
    • Active transport (against concentration gradient, requiring energy).

Organisation in Animals & Plants

  • Organ systems work together to keep organisms alive.
  • Human digestive system breaks down food using enzymes.
  • The circulatory system moves blood around the body.
  • In plants:
    • Xylem transports water.
    • Phloem transports food.

Infection & Response

  • Pathogens (bacteria, viruses, fungi, and protists) cause disease.
  • The body defends itself using physical barriers and the immune system (white blood cells).
  • Vaccines introduce inactive pathogens to stimulate immunity.
  • Antibiotics kill bacteria, but not viruses.

Bioenergetics

  • Photosynthesis converts light energy into glucose in plants.
  • Factors affecting photosynthesis: light, CO2CO_2, and temperature.
  • Respiration releases energy from glucose in cells.
    • Aerobic uses oxygen.
    • Anaerobic doesn't use oxygen.

Homeostasis & Response

  • The body maintains stable internal conditions (homeostasis) through systems like the nervous system (fast) and endocrine system (slow).
  • Reflex actions are quick, automatic responses.
  • Hormones control processes like blood sugar and the menstrual cycle.

Inheritance, Variation & Evolution

  • DNA is the molecule carrying genetic information in chromosomes.
  • Inheritance involves passing traits through genes.
  • Variation comes from genetics and environment.
  • Evolution happens through natural selection, where beneficial traits become more common over generations.

Ecology

  • Ecology studies how organisms interact with their environment.
  • Food chains show energy transfer.
  • Biodiversity means variety in living things and is vital for ecosystem stability.
  • Human actions like pollution and deforestation harm ecosystems.

Chemistry

Atomic Structure

  • Atoms are made of protons, neutrons, and electrons.
  • The nucleus contains protons and neutrons, with electrons orbiting.
  • The number of protons defines the element.
  • Isotopes are atoms of the same element with different numbers of neutrons.

The Periodic Table

  • Organises elements by atomic number.
  • Groups are columns (similar properties) and periods are rows.
  • Group 1 are reactive metals, Group 7 are halogens, and Group 0 are unreactive noble gases.

Bonding, Structure & Properties

  • Ionic bonding involves the transfer of electrons between metals and non-metals.
  • Covalent bonding is the sharing of electrons between non-metals.
  • Metallic bonding involves positive ions in a sea of delocalised electrons.
  • Bonding affects a substance's properties.

Chemical Calculations

  • Relative formula mass (MrM_r) is the sum of atomic masses in a compound.
  • Moles measure the amount of substance.
  • Equations can be balanced to calculate masses and volumes in reactions.

Chemical Changes

  • Reactivity series ranks metals by how easily they form positive ions.
  • Displacement reactions occur when a more reactive metal replaces a less reactive one.
  • Electrolysis uses electricity to break down compounds.

Energy Changes

  • Reactions release (exothermic) or absorb (endothermic) energy.
  • Exothermic reactions feel hot (e.g. combustion), endothermic reactions feel cold (e.g. dissolving salts in water).

Rates of Reaction

  • Rate is how quickly a reaction happens.
  • Factors: temperature, concentration, surface area, and catalysts.
  • Collision theory explains how particles must collide with enough energy to react.

Organic Chemistry

  • Study of carbon compounds.
  • Alkanes are saturated hydrocarbons.
  • Alkenes are unsaturated with double bonds.
  • Crude oil is separated by fractional distillation and used for fuels and plastics.

Chemical Analysis

  • Pure substances have fixed properties.
  • Chromatography separates mixtures.
  • Gas tests identify gases like hydrogen (pop test), oxygen (relights splint), and CO2CO_2 (limewater turns cloudy).

The Atmosphere

  • Earth's atmosphere evolved from volcanoes to today's composition: nitrogen (78%), oxygen (21%).
  • Greenhouse gases (CO2CO_2, methane) trap heat, causing climate change.

Using Resources

  • Water is treated to make it potable.
  • Waste water is cleaned before release.
  • Life cycle assessments evaluate the environmental impact of products from creation to disposal.

Physics

Energy

  • Energy can be stored in different ways: kinetic, thermal, chemical, elastic, gravitational.
  • Energy is transferred by heating, waves, electricity, and forces.
  • Efficiency measures useful energy output.

Electricity

  • Current is the flow of charge.
  • Voltage is the energy per charge.
  • Resistance opposes current.
  • Series circuits have one path; parallel circuits have multiple paths.
  • Power is calculated using P=IVP = IV.

Particle Model of Matter

  • Solids, liquids, and gases behave differently based on particle arrangement.
  • Heating increases internal energy.
  • Specific heat capacity is the energy to raise 1kg by 1°C.

Atomic Structure

  • Models of the atom changed over time.
  • Radioactive decay involves unstable nuclei emitting alpha, beta, or gamma radiation.
  • Half-life measures how long it takes for half the atoms to decay.

Forces

  • A force is a push or pull.
  • Scalar quantities have size; vector quantities have size and direction.
  • Newton's Laws describe motion.
  • Work done is force times distance.
  • Speed and acceleration describe motion changes.

Waves

  • Waves transfer energy.
  • Properties: wavelength, frequency, amplitude, speed.
  • EM spectrum includes radio waves to gamma rays.
  • Different types have different uses and dangers (e.g. UV causes skin damage).

Magnetism & Electromagnetism

  • Magnets have north and south poles.
  • Magnetic fields show the area of force.
  • Electromagnets use electric current to create a magnetic field, useful in motors and cranes.