Scientific Method of Investigation

Chemistry is a practical subject. Scientists use a step-by-step process called the scientific method to solve problems and answer questions about the natural world.

Stages of Scientific Investigation

1. Identify a Problem

   This step involves asking a scientific question about something you observe.
   Examples of questions:

   • What causes rusting?

   • Why do plastics not decompose easily?

2. Form a Hypothesis

   A hypothesis is a possible answer to the question. It is based on what the scientist already knows.
   Example:

   • “Rusting happens faster in salty water than in fresh water.”

3. Test the Hypothesis (Experiment)

   An experiment is done to test whether the hypothesis is correct. The experiment must be planned carefully.

   Types of Variables in an Experiment:

   • Independent Variable: The one thing you change.
     Example: Type of water (fresh or salty)

   • Dependent Variable: What you measure or observe.
     Example: Amount of rust formed

   • Controlled Variables: Things you keep the same.
     Example: Same type of metal, same amount of water, same temperature

4. Analyse the Results

   After the experiment, collect and study the data. This means checking what happened and why.

5. Draw a Conclusion

   Use the results to make a conclusion.

   • If the results support the hypothesis, the hypothesis is accepted.

   • If the results do not support it, the hypothesis is rejected.
     In that case, a new hypothesis can be made and tested again.

Summary Example:

Problem: Why does iron rust?
Hypothesis: Iron rusts faster in salty water.
Experiment: Place iron nails in fresh water and salty water.
Results: More rust in salty water.
Conclusion: The hypothesis is correct — salt speeds up rusting.