Year 7 Science Notes (copy)

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.

  • Respiratory System: Gas exchange.

    • Inhaled air: More oxygen. Exhaled air: More carbon dioxide.

  • Cardiovascular system: pumps blood around body

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

  • Opaque: does not let light travel through it

  • Translucent: lets some light travel through it

  • Transparent: lets light travel through it

  • Refraction: Light changes speed and direction when passing between different density substances.

  • Light can travel in a vacuum (doesn’t need medium to travel)

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).

  • Vacuum: a space without particles (e.g. space)

  • 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: $$340 m/