# Planning an Investigation

> Research, hypotheses, variables, safety, and how to write a method someone else can follow.

From HSC Chemistry on WhizzNotes, free study notes for NSW students: https://whizznotes.com/chemistry/planning-investigations/. Updated 3 November 2026.
Year 11 and Year 12 boxes go deeper than the Year 10 text around them.

### Story time: The fizzy tablet race
Noah noticed something at breakfast. His dad dropped a fizzy vitamin tablet into a glass of hot tea by mistake, and it disappeared in seconds. The tablet in Noah's cold water took nearly a minute.

"Does hot water make it fizz faster?" he wondered.

His older sister Lina, who was in Year 11, said: "Maybe. But you need a plan, not a hunch. Same tablets, same amount of water, only the temperature changes. Time each one. Do it three times."

Noah wrote a question, a guess, a list of equipment and a step by step method. Then he tested it. This chapter shows you how to plan like Noah and Lina.

**In short:** Planning an investigation means turning a question into a fair test: write a hypothesis (If... then... because...), change one variable, measure one, and keep the rest the same. A good method has numbered steps with exact amounts, plus a risk assessment for each hazard.

## The steps of an investigation

Every good investigation follows the same path.

1. **Ask a question** you can test. "Does water temperature affect how fast a tablet dissolves?"
2. **Research** what is already known.
3. **Write a hypothesis**: a prediction you can test.
4. **Identify the variables.**
5. **Plan the method** and list the materials.
6. **Do a risk assessment.**
7. **Collect and record data.**
8. **Analyse** the data and **draw a conclusion.**
9. **Evaluate** the method and suggest improvements.

## Research first

Before you test anything, find out what scientists already know. Your research can come from two kinds of data.

| Type | Meaning | Example |
|---|---|---|
| **Primary data** | Data **you** collect yourself in your own experiment | Noah's timings with a stopwatch |
| **Secondary data** | Data someone **else** collected | A table of solubility values in a textbook or on a science website |

Not all secondary sources are good. Ask these questions about a source:

- **Relevant**: does it answer my question?
- **Reliable**: is it from an expert source (a university, a government science body, a textbook)? Do other sources agree?
- **Up to date**: when was it written?
- **Unbiased**: is someone trying to sell something?

### Exam tip: The two source rule
If two or more trusted sources give the same information, you can be more confident it is reliable. One random blog post is weak evidence.

## Writing a hypothesis

A **hypothesis** is a testable prediction with a reason. A good pattern is:

> **If** I change ___, **then** ___ will happen, **because** ___.

Noah's hypothesis: "**If** the water temperature is increased, **then** the tablet will dissolve faster, **because** particles in hot water move faster and hit the tablet more often."

A hypothesis does not have to be right. An experiment that proves your hypothesis wrong is still a successful experiment. You learned something.

## Variables

| Type | Meaning | In Noah's test |
|---|---|---|
| **Independent** | What you change on purpose | Water temperature |
| **Dependent** | What you measure | Time for the tablet to dissolve |
| **Controlled** | What you keep the same | Volume of water, type of tablet, size of glass, no stirring |

Only the independent variable changes. That makes it a **fair test**.

A **control** (or control group) is a test you compare against, where the independent variable is not applied. For example, a tablet in room temperature water could be the normal case you compare hot and cold water against.

## Materials and method

The **materials** (or equipment) list names everything, with sizes and amounts.

- 3 identical fizzy vitamin tablets per temperature
- 250 mL beaker
- 100 mL measuring cylinder
- Thermometer
- Kettle and ice
- Stopwatch

The **method** is a numbered list of steps. Someone who has never met you should be able to follow it and get the same results.

1. Measure 100 mL of water at 20 °C using the measuring cylinder and pour it into the beaker.
2. Check the temperature with the thermometer.
3. Drop in one tablet and start the stopwatch at the same moment.
4. Stop the stopwatch when no solid is left.
5. Record the time in a results table.
6. Repeat steps 1 to 5 two more times.
7. Repeat the whole test at 40 °C, 60 °C and 80 °C.

### Key idea: What makes a good method
- Numbered steps, one action per step.
- Exact amounts and units ("100 mL", not "some water").
- Names the equipment used to measure.
- Says how many times to repeat.
- Written so it can be **copied** exactly by someone else.

## Risk assessment

A **risk assessment** lists each hazard, the risk it causes, and how you will stay safe.

| Hazard | Risk | Safety step |
|---|---|---|
| Hot water at 80 °C | Burns to skin | Use a beaker with tongs, keep away from the edge of the bench |
| Glass beaker | Cuts if broken | Report breaks, use a dustpan, not hands |
| Chemicals in the tablet | Eye irritation | Wear safety glasses |

### Watch out: A method is not a story
Do not write "First I got some water and then we put the tablet in and it fizzed a lot." That is a report of what happened. A method is a set of **instructions** with exact amounts, written in steps.

**Mind map**

```text
Planning an investigation
  Question and research
    Primary data: you collect
    Secondary data: others collect
    Check source is reliable
  Hypothesis
    If... then... because...
    Must be testable
  Variables
    Independent: change
    Dependent: measure
    Controlled: keep same
  Method
    Numbered steps
    Exact amounts and units
    Repeat trials
  Safety
    Hazard, risk, precaution
```

### Year 11: Validity starts at the planning stage
A **valid** experiment really tests the hypothesis. Validity is decided **before** you start, by the method you choose.

- Control every variable that could change the dependent variable.
- Pick a method that measures the right thing. Timing "until no solid is left" is better than "until it stops fizzing", because fizzing can stop before the tablet is gone.
- Choose a sensible **range** (20 °C to 80 °C) and enough **intervals** (at least 4 or 5 values) to see a trend.

A good plan also says how data will be recorded: a table with the independent variable in the first column, units in the headings, and space for repeats and an average.

### Year 12: Hypotheses you can falsify
Scientists say a good hypothesis must be **falsifiable**: there must be some possible result that would prove it wrong. "Hot water changes the tablet in some way" cannot really fail, so it is a weak hypothesis. "Raising the temperature by 20 °C halves the dissolving time" makes a sharp prediction that the data can test.

In senior chemistry you will often state a **null hypothesis**: "Temperature has no effect on dissolving time." The experiment then looks for evidence strong enough to reject it.

## Quick summary

- An investigation goes: question, research, hypothesis, variables, method, risk assessment, data, conclusion, evaluation.
- **Primary data** you collect. **Secondary data** someone else collected. Check secondary sources are relevant, reliable, recent and unbiased.
- Hypothesis pattern: **If... then... because...**
- Change **one** variable (independent), measure one (dependent), keep the rest the same (controlled).
- A method is numbered steps with exact amounts, so anyone can repeat it.
- A risk assessment names each hazard and how to reduce the risk.

## Quiz

Try these questions from the chapter quiz.

1. Which of these is a testable hypothesis?
   - A. Chemistry is interesting
   - B. If the amount of salt is increased, then the boiling point of water will rise, because salt particles get in the way of water escaping
   - C. Water is wet
   - D. I think something will happen to the water
   - Answer: B. If the amount of salt is increased, then the boiling point of water will rise, because salt particles get in the way of water escaping. A hypothesis must be a clear prediction you can test, ideally with a reason.

2. Noah times how long a tablet takes to dissolve at different water temperatures. The time taken is the:
   - A. Independent variable
   - B. Dependent variable
   - C. Controlled variable
   - D. Hypothesis
   - Answer: B. Dependent variable. The time is what he measures, so it is the dependent variable.

3. Which is a controlled variable in Noah's test?
   - A. Water temperature
   - B. Time to dissolve
   - C. Volume of water
   - D. The hypothesis
   - Answer: C. Volume of water. The volume of water stays the same in every trial.

The whole chapter quiz is on the page, for signed-in students: https://whizznotes.com/chemistry/planning-investigations/#quiz