Worksheets › Class 9 › Exploration: Entering the World of Secondary Science › Cheat sheet
Class 9 Exploration: Entering the World of Secondary Science: cheat sheet
CBSE Science. How science works: models, precise language and units, maths as relationships, laws, theories and principles, predictions, estimation and testing claims.
Key ideas
- A scientific model is a simplified picture that keeps only what matters for the question, such as a car treated as a point on a long journey.
- Science uses precise symbols and standard (SI) units so that everyone measures and communicates the same way; mixing units causes real mistakes.
- An equation shows how quantities are related: if y depends on the square of x, doubling x makes y four times as large.
- A law describes a pattern, a theory explains why it happens, and a principle is a broad guiding idea like the conservation of energy.
- A prediction is a reasoned expectation from evidence; when it fails, scientists look deeper. No theory is final.
- A rough estimate, made by multiplying sensible round numbers, shows the size of an answer and catches big mistakes.
- To check a claim, turn it into a testable question and design a fair test that changes only one thing.
Remember
| Speed | km/h × 5/18 = m/s |
| Prefixes | kilo = 10³, centi = 10⁻², milli = 10⁻³, micro = 10⁻⁶ |
| Volume | 1 L = 1,000 mL; 1 m³ = 1,000 L |
| Scaling | y ∝ x² and x doubles → y × 4; y ∝ 1/x and x doubles → y halves |
Watch out
- Thinking a theory is just a guess (it is a well-tested explanation).
- Treating a model as an exact copy of the real thing.
- Writing an estimate with too many digits, or forgetting the unit.
Worked example
The kinetic energy of a moving ball is 80 units, and it depends on its speed, as its square. Find the new kinetic energy if its speed becomes 1/2 of what it was.
Working: squared: (1/2)² = 1/4; new = 80 × 1/4 = 20
Answer: 20 units
Practise Exploration: Entering the World of Secondary Science
Revise with this page, then practise: every Exploration: Entering the World of Secondary Science sheet in the app is new, with an answer key and working.
Coming soon for Android and iPhone.