# Ch 1 Introducing Science

F.1 Integrated Science · 1.1 Learning Science · 1.2 Working like a Scientist · Lesson 1

What science is, what scientists do, and how to run a fair test.

## Key points

- **Science ／ 科學** is the study of nature: **why** and **how** things happen around us. Main branches: physics, chemistry, biology, geology, astronomy.
- Scientists gather **evidence**, test hypotheses and share knowledge. Scientific knowledge can **change** when new evidence appears.
- **Five steps** of an investigation: observe and ask a question → background research → propose a **hypothesis ／ 假設** → design and do a fair experiment → analyse results and conclude.
- A hypothesis is a **reasonable answer** based on observation and knowledge, and must be **testable and measurable**. Results do not support it? Revise the hypothesis, never the results.
- **Discovery** = finding something that already exists in nature. **Invention** = making something new. **Technology ／ 科技** = using scientific knowledge to solve problems or make products.
- Science has **limitations**: never 100 % accurate, cannot explain everything. **Misuse** (nuclear weapons, drug abuse) is a different problem.
- Working like a scientist: **fair testing**, **pattern seeking**, **classifying**, **model building**. Never taste anything in the laboratory.

## Must know

| Variable | Also called | What it means | Bean-plant example |
|---|---|---|---|
| **Independent** | Variable to be changed | The one thing we change between set-ups (only one!) | Amount of water each day |
| **Dependent** | Variable to be compared | What we measure to see the effect | Height after two weeks |
| **Controlled** | Variables to be kept constant | Everything else, kept the same so the test is fair | Type of bean, pot, soil, sunlight |

## Common mistakes

- ✗ "The candle needs air to burn" is an observation. ✓ An observation is what you see, hear or measure ("the candle went out under the jar"). The explanation is a **hypothesis**.
- ✗ "Penicillin was invented." ✓ Things already in nature are **discovered**; things people make (light bulbs, smartphones) are **invented**.
- ✗ "The controlled variable is the one I change." ✓ Controlled variables are kept the **same**. The one you change is the **independent** variable.
- ✗ Changing two things at once between set-ups. ✓ Only **one** independent variable, or you cannot tell which change caused the result.
- ✗ Pendulum: "Independent: time for 10 swings. Dependent: length of string." ✓ Swapped. You **change** the length (independent) and **measure** the time (dependent).

## Quick check

1. A student says, "Plants grow taller when they get more sunlight." Is this an observation or a hypothesis?
2. A test asks whether a can's colour affects how fast the water inside warms in the sun. Name the independent variable and two controlled variables.
3. Is a new species of deep-sea fish a discovery or an invention?

## Answers

1. A hypothesis: a possible explanation that can be tested, not something directly seen or measured.
2. Independent: colour of the can. Controlled: volume of water, starting temperature, size of can, time in the sun (any two).
3. A discovery. It already existed in nature.

## Did you know?

Marie Curie's notebooks are still radioactive more than 100 years after she used them. They are kept in lead-lined boxes, and visitors must sign a form before they are allowed to read them.