Year 7 Science - Term 3 Examination Revision Notes

7La. Making Sounds

  • Sound is a form of energy. It travels through a medium like air, water, or solids as vibrations or waves.

7Lb. Moving Sound

  • Properties of Sound:
    • Frequency: Number of waves passing a point in 1 second, measured in Hertz (Hz).
    • Amplitude: Height of the wave, indicating the energy or strength of the sound.
    • Wavelength: Distance between two consecutive compressions or rarefactions.
  • Pitch and Frequency:
    • Pitch is how high or low a sound seems.
    • Frequency determines the pitch.
      • High frequency = High pitch (e.g., whistle).
      • Low frequency = Low pitch (e.g., drum).
  • Loudness and Amplitude:
    • Loudness refers to how strong or soft a sound appears to our ears.
    • Loudness depends on the amplitude of the wave.
      • Greater amplitude = Louder sound.
      • Smaller amplitude = Softer sound.
  • Finding Amplitude from a Wave Graph:
    • Measure the maximum height of the wave from the central line (rest position).
    • Example: Amplitude = 3
    • Number of complete waves in 5 seconds = 1 second

7Lc. Detecting Sound

  • How We Hear:
    • Sound waves enter the ear canal and reach the eardrum, causing it to vibrate.
    • These vibrations are amplified by three tiny bones in the middle ear.
    • The amplified vibrations pass into the cochlea in the inner ear, where they are converted into electrical impulses.
    • These impulses are transmitted to the brain through the auditory nerve, allowing the brain to hear and interpret the sound.

7Da. Variation

  • Variation: Differences between individuals of the same species (e.g., eye color, height in humans).
    • Continuous variation.
    • Discontinuous variation.

7Db. Adaptations

  • Adaptations: Features that help organisms survive in their habitat.
  • Example: Elephant adaptations:
    • Trunk:
      • Works like a hand and a nose.
      • Helps keep the elephant cool.
      • Also used to scare away animals.
      • Protects the elephant from sun, heat, and insect bites.
      • Helps them move trees and stay safe from predators.
      • Help them walk quietly and not sink in mud or sand.
      • Used for eating, drinking, smelling, and bathing.
    • Big Ears
    • Thick Skin
    • Strong Legs and Big Body
    • Soft-Padded Feet

7De. Transfers in Food Chain

  • Food Chain: Shows how energy flows from one organism to another.
    • Example: Grass → Grasshopper → Frog → Snake → Eagle
    • Trophic levels:
      • Producers (plants)
      • Primary consumers (herbivores)
      • Secondary consumers (carnivores)
      • Tertiary consumers (top predators)
  • Food Web: A network of many interconnected food chains in an ecosystem.
  • Pyramid of Numbers: Shows the number of organisms at each trophic level.
    • Usually widest at the bottom (more producers) and narrow at the top (fewer top predators).
  • Energy Transfer in a Food Chain:
    • Only about 10% of energy is passed on from one trophic level to the next.
    • The rest is lost as heat, movement, or waste.

Ecosystem

  • Ecosystem: A community of living organisms (plants, animals, and microbes) interacting with each other and with their non-living environment (air, water, soil) in a particular area.
  • Examples: A forest, pond, desert, or coral reef.
  • Species: A group of organisms that can reproduce and have fertile offspring. Examples: Humans, dogs, oak trees.
  • Population: All the members of a species living in a particular area. Example: All frogs in a pond.
  • Community: All the different populations living together in an area. Example: Frogs, fish, algae, and insects in a pond.
  • Hybrids: Offspring resulting from the mating of two different species.
    • Example: A zebroid (Zebra X Horse) or a mule (horse × donkey). Hybrids cannot reproduce
  • Habitat: The natural home or environment of an organism.
    • Example: Polar bears live in cold Arctic habitats.

Atoms, Elements, and Compounds

  • Atoms and Elements
    • All substances are made up of atoms.
    • An element is made up of only one type of atom.
    • Atoms and elements are building blocks of matter.
    • There are 90 different types of atoms found naturally anywhere on the earth. They are listed in a table called the periodic table.
  • Molecules
    • Atoms are held together in groups called molecules.
    • Molecules can consist of the same type or different types of atoms.
    • Oxygen and nitrogen are examples of molecules that have two atoms joined together.
  • Compound
    • When two (or more) elements are chemically joined together they form compounds.
    • Example: Water molecules (H2O) consist of 2 Hydrogen atoms and 1 Oxygen atom. Carbon dioxide (CO2) consists of 1 Carbon atom and 2 Oxygen atoms.
  • Mixture
    • A mixture contains two or more substances that are not joined together. They can be separated.
    • An alloy is a mixture that contain two types of metal atoms.