Year 7 Science Notes

Microscope & Cells

  • Use the lowest magnification first for the widest view.
  • Organelles:
    • Nucleus: Contains genetic material, controls the cell.
    • Cell Membrane: Controls substance movement in/out.
    • Cytoplasm: Chemical reactions occur.
    • Mitochondria: Energy release (respiration).
    • Ribosome: Protein synthesis.
    • Cell Wall: Strength and support (plant cells).
    • Chloroplast: Photosynthesis (plant cells).
    • Vacuole: Contains cell sap.
  • Cell: Basic structural unit.
  • Tissue: Similar cells with a function.
  • Organ: Different tissues for a job.
  • Organ System: Different organs for a job.
  • Unicellular: One cell. Multicellular: Many cells.
  • Specialized Cells: Root hair cell (water absorption), Sperm cell (streamlined), Palisade cell (photosynthesis).

Systems

  • Digestive System: Breaks down food molecules.
    • Adaptations: Folded intestine with villi/microvilli increasing surface area for diffusion, thin membranes, many blood vessels.
  • Respiratory System: Gas exchange.
    • Adaptations: Trachea (C-ring cartilage), Alveoli (thin membranes, good blood supply, folded membrane).
    • Inhaled air: More oxygen. Exhaled air: More carbon dioxide.

States of Matter

  • Conservation of Mass: Mass stays constant during state changes.
  • Solids: Fixed shape, cannot be compressed.
  • Liquids: Flow, take container shape, cannot be compressed.
  • Gases: Flow, fill container, can be compressed.
  • Changes of State:
    • Melting: Solid to liquid (gaining energy).
    • Boiling/Evaporating: Liquid to gas (gaining energy).
    • Freezing: Liquid to solid (losing energy).
    • Condensing: Gas to liquid (losing energy).
  • Diffusion: Movement from high to low concentration in liquids/gases.
  • Gas Pressure: Particles hitting container walls.

Mixtures & Separation

  • Pure Substance: One type of particle.
  • Mixture: More than one type of particle, not chemically joined.
  • Chromatography: Separates dissolved substances based on dissolving ability.
  • Solution: Solute (dissolves) in Solvent.
  • Saturated: No more solute can dissolve.
  • Distillation: Separates solvent from solution (based on boiling point).
  • Evaporation: Separates soluble solid from liquid.
  • Filtration: Separates insoluble solid from liquid (residue stays, filtrate passes through).

Forces & Motion

  • Forces measured in Newtons (N).
  • Pressure: p=F/Ap = F/A (Pressure = Force/Area).
  • Weight: W=m×gW = m \times g (Weight = mass x gravitational field strength).
  • Earth's gravitational field strength: 9.8N/kg9.8 N/kg.
  • Speed: Speed (m/s) = distance (m) / time (s).
  • Balanced forces: Stationary or constant speed.
  • Unbalanced forces: Acceleration, deceleration, or direction change.

Light

  • Ray Diagrams: Show light travel using straight lines with arrowheads.
  • Law of Reflection: Angle of incidence (i) = angle of reflection (r).
  • Diffuse Scattering: Reflection off rough surfaces in all directions.
  • Refraction: Light changes speed and direction when passing between different density substances.
  • Plane Mirror: Flat mirror, image appears behind, right way up, laterally inverted.

Waves & Sound

  • Waves transfer energy.
  • Longitudinal Waves: Vibrations parallel (e.g., sound).
  • Transverse Waves: Vibrations perpendicular (e.g., light).
  • Sound needs medium (solid, liquid, gas).
  • Ears: Eardrum vibrates, ossicles transfer vibrations to cochlea, signals to brain.
  • Amplitude: Loudness. Wavelength: Distance between crests. Frequency: Pitch (Hertz).
  • Reflection (Sound): Echoes.
  • Ultrasound: >20,000 Hz (Uses: Check health of unborn babies, clean jewellery).
  • Speed of Sound: 340m/s340 m/s
  • White Light: Mixture of colors; split by prism (dispersion).
  • Primary Colors (Light): Red, Green, Blue (combine to make secondary colors).
  • Object Color: Reflected color.