Year 7 Science Comprehensive Study Guide

Revision Overview & Curriculum Topics

• The science revision curriculum covers $4$ core topics:
  • Section $1$: Observing the Universe
  • Section $2$: Forces
  • Section $3$: Classification
  • Section $4$: Scientific Investigation Skills

Section 1: Observing the Universe

• Key Vocabulary:

  • Astronomy: The scientific study of stars, planets, and space.
  • Telescope: An instrument that collects and magnifies light (or other waves) to observe distant objects.
  • Observatory: A building or site equipped with telescopes for observing space.
  • Light-year: The distance light travels in one year — used to measure huge distances in space.
  • Solar system: The Sun and everything that orbits it, including planets, moons, asteroids, and comets.
  • Galaxy: A huge collection of billions of stars, gas, and dust held together by gravity.

• Instruments of Observation:

  • Naked eye: Humans have observed stars and planets for thousands of years without any instrument, but can only see the brightest and closest objects.
  • Optical telescopes: Use lenses or mirrors to collect and magnify visible light, making distant objects appear bigger and brighter.
  • Radio telescopes: Detect radio waves (rather than visible light) coming from space; they can operate day or night and function through cloud cover.
  • Space telescopes (e.g., Hubble): Orbit above Earth's atmosphere, successfully avoiding the atmospheric blurring and light pollution encountered by ground-based telescopes.

• Objects Within the Universe:

  • Stars: Huge balls of hot gas that produce their own light and heat through nuclear fusion.
  • Planets: Large objects that orbit a star. They do NOT produce their own light; they are visible because they reflect sunlight.
  • Meteoroids, Meteors, and Meteorites:
  • Meteoroid: A small rocky or metallic object in space.
  • Meteor: The streak of light (commonly called a "shooting star") produced as a meteoroid burns up upon entering the atmosphere.
  • Meteorite: The surviving fragment of a meteoroid that endures atmospheric passage and lands on the ground.
  • Asteroids: Rocky objects, generally smaller than planets, mostly concentrated in the asteroid belt between Mars and Jupiter.
  • Comets: Icy objects that develop a visible glowing tail when passing close to the Sun.

• Section 1 Revision & Practice Questions:

  • Question $1$: What is astronomy?
  • Question $2$: Name TWO instruments used to observe space, and explain ONE advantage of each.
  • Question $3$: Explain the difference between a meteoroid, a meteor, and a meteorite.
  • Question $4$: Why do planets not produce their own light, but we can still see them?
  • Question $5$: Explain ONE advantage of a space telescope compared to a ground-based telescope.
  • Question $6$: What is a light-year, and why do scientists use it instead of kilometres?
  • Question $7$: How do stars produce their own light and heat?
  • Question $8$: What is the difference between a radio telescope and an optical telescope?
  • Question $9$: Where is the asteroid belt located?
  • Question $10$: What causes a comet to develop a glowing tail?
  • Question $11$: Define solar system and galaxy, and explain which one is larger.

Section 2: Forces

• Fundamental Concept of Forces:

  • A force is defined as a push or a pull.
  • A force can change three distinct aspects of an object:
  • Speed
  • Direction
  • Shape

• Categorization of Forces:

  • Contact Forces (require physical contact between surfaces or objects):
  • Friction: Resists movement between contacting surfaces.
  • Applied force: A direct push or pull exerted on an object.
  • Air resistance: Slows objects moving through air.
  • Tension: Pulling force transmitted through a rope, string, or cable.
  • Normal force: A supporting surface pushing back against an object resting on it.
  • Non-Contact Forces (act at a distance without requiring physical contact):
  • Gravity: Pulls objects toward each other.
  • Magnetism: Attracts or repels magnetic materials.
  • Electrostatic force: Attracts or repels charged objects.

• Measurement of Forces:

  • Units: Forces are measured in Newtons ($\text{N}$), named after Sir Isaac Newton.
  • Measuring Instrument: A newton meter (also termed a spring scale or force meter) is used to measure force.
  • Operation: The applied force stretches an internal spring, and the calibrated scale indicates the magnitude of the force in newtons ($\text{N}$).

• Section 2 Revision & Practice Questions:

  • Question $1$: Define what a force is.
  • Question $2$: List THREE things a force can change about an object.
  • Question $3$: Give TWO examples of contact forces and TWO examples of non-contact forces.
  • Question $4$: What instrument is used to measure force, and what unit does it use?
  • Question $5$: Explain why gravity is classified as a non-contact force.
  • Question $6$: Explain what friction does, and give ONE everyday example of it.
  • Question $7$: What is air resistance, and how does it affect a falling object?
  • Question $8$: Explain the difference between a contact force and a non-contact force.
  • Question $9$: A book rests on a table. Name the force the table applies to the book.
  • Question $10$: Why is magnetism classified as a non-contact force?
  • Question $11$: A student pulls a rope. Name the force acting through the rope.

Section 3: Classification

• Principles of Physical & Structural Classification:

  • Living organisms are grouped based on shared observable physical and structural features, such as body shape, number of legs, or the presence of fur, feathers, or scales.
  • Organisms that share a higher number of common features are more closely related in biological classification.

• Binomial Nomenclature:

  • Every species is assigned a two-part scientific name under the system of binomial nomenclature.
  • Genus: The first part of the scientific name; it always begins with a capital letter.
  • Species: The second part of the scientific name; it is always written in lowercase.
  • Formatting: Both components are formatted in italics when typed (or underlined when handwritten).
  • Example: Homo sapiens (humans).

• Cell Types and Structural Differences:

  • Cells constitute the basic unit of life across all living organisms.
  • Plant Cells:
  • Possess a rigid cell wall.
  • Possess chloroplasts for photosynthesis.
  • Typically contain a large central vacuole.
  • Generally maintain a fixed box-like shape.
  • Animal Cells:
  • Do NOT possess a cell wall or chloroplasts.
  • Typically present an irregular, flexible round shape.
  • Shared Structures (Present in BOTH Plant and Animal Cells):
  • Cell membrane: Regulates movement of substances in and out of the cell.
  • Cytoplasm: Gel-like substance where chemical reactions take place.
  • Nucleus: Controls cell activities and contains genetic information.
  • Mitochondria: Site of cellular respiration to release energy.

• Section 3 Revision & Practice Questions:

  • Question $1$: Why do scientists classify living things?
  • Question $2$: Give TWO examples of physical features used to classify organisms.
  • Question $3$: What does binomial nomenclature mean?
  • Question $4$: Write the rules for writing a binomial (scientific) name correctly.
  • Question $5$: Rewrite this name correctly: homo Sapiens
  • Question $6$: In the name Panthera leo, which part is the genus and which is the species?
  • Question $7$: List TWO structures found in a plant cell but NOT in an animal cell.
  • Question $8$: List TWO structures found in BOTH plant and animal cells.
  • Question $9$: Explain the function of the cell wall, and why animal cells do not need one.
  • Question $10$: Explain the function of the chloroplast.
  • Question $11$: A cell is observed with a cell wall and chloroplasts. Is it a plant or animal cell? Explain how you know.

Section 4: Scientific Investigation Skills

• Experimental Variables:

  • Independent Variable: The ONE variable that is deliberately changed or tested during an experiment.
  • Dependent Variable: The variable that is MEASURED — the outcome that directly depends on changes in the independent variable.
  • Controlled Variable(s): All other parameters that are kept strictly the SAME to maintain a fair test.

• Design of Fair Tests:

  • A fair test isolates the independent variable by keeping all controlled variables constant.
  • This ensures that any observed changes in the dependent variable can be attributed solely to the independent variable rather than extraneous factors.

• Tables & Graphical Representations:

  • Data Tables:
  • Used to organize raw data systematically.
  • Must always include descriptive column headings and explicit units of measurement (e.g., "Time ($\text{s}$)").
  • Line Graphs:
  • Utilized for displaying continuous data (data that can assume any numerical value, such as temperature or time).
  • Bar Graphs:
  • Utilized for displaying categorical data (data grouped into discrete, non-numerical categories, such as plant species).
  • Axis Convention:
  • The $x$--axis (horizontal) displays the independent variable.
  • The $y$--axis (vertical) displays the dependent variable.

• Quality Criteria in Scientific Investigations:

  • Reliability: Achieving consistent, repeatable results across multiple experimental trials.
  • Accuracy: The proximity of a measured value to the true, actual value.
  • Validity: The degree to which an experiment measures what it intends to measure, dependent on maintaining a strictly fair test.

• Section 4 Revision & Practice Questions:

  • Question $1$: Define independent variable and dependent variable, using an example.
  • Question $2$: What is a controlled variable? Give an example.
  • Question $3$: Explain what makes an investigation a fair test.
  • Question $4$: Why is it important to only change ONE variable at a time?
  • Question $5$: Would you use a line graph or a bar graph to show plant height over $5\text{ weeks}$? Explain why.
  • Question $6$: Would you use a line graph or a bar graph to compare heights of $5$ different plant species? Explain why.
  • Question $7$: Which axis does the independent variable go on?
  • Question $8$: Name TWO things every data table should include.
  • Question $9$: Explain the difference between reliability and accuracy.
  • Question $10$: What does it mean if an investigation is valid?
  • Question $11$: A student repeats their experiment $3\text{ times}$. Which quality does this improve, and why?