Planning an Investigation

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.

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?

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

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.

Risk assessment

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

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