1.2 - Scientific Investigation in Chemistry

Scientific Investigation and Scientific Method

• A scientific investigation uses a scientific method to solve a problem in science and generally begins by observing a problem.
• The scientific method is a systematic method used by scientists or researchers to solve science-related problems correctly.

Steps in the scientific method

1. Make observations: Use sight, hearing, touch, taste or smell to gather information about an object or phenomenon.
2. Make an inference: Use collected data and past experience to propose a conclusion and explanation for an event.
3. Identify the problem: Ask a question based on the inference.
4. Make a hypothesis: State a testable general relationship between the manipulated and responding variables that explains an event or observation.
5. Identify the variables: Identify the manipulated, responding and fixed variables needed to test the hypothesis.
6. Control the variables: Manipulate one variable, observe its relationship with the responding variable and keep the other variables fixed.
7. Plan the experiment: Determine the materials, apparatus, procedure, data-collection method, and method for analysing and interpreting data.
8. Collect data: Make observations or measurements and record them systematically.
9. Interpret data: Organise and interpret the data through calculations, graphs or charts to determine relationships between variables.
10. Make a conclusion: Decide from the findings whether the hypothesis is accepted or rejected.
11. Prepare a report: Communicate every aspect of the experiment in detail so the findings can be shared to develop chemistry knowledge.

Experiment 1.1: Effect of Temperature on the Solubility of Salt

Aim: To study the effect of temperature on the solubility of salt in water.

Problem statement: Does the temperature of water affect the solubility of salt in water?

Hypothesis: An increase in water temperature increases the solubility of salt in water.

Variables

• Manipulated: Temperature of water
• Responding: Solubility of salt in water
• Fixed: Volume of water, mass of salt and time

Materials: Distilled water and salt.

Apparatus: $150\mathrm{c}{\mathrm{m}}^3$ beaker, $100\mathrm{c}{\mathrm{m}}^3$ measuring cylinder, thermometer, electronic scale, glass rod, Bunsen burner, stopwatch, wire gauze and tripod stand.

Apparatus arrangement: Place the beaker on wire gauze supported by a tripod stand above the Bunsen burner. Use the thermometer to measure the water temperature and the glass rod to stir the salt and water.

Procedure

1. Measure $50\mathrm{c}{\mathrm{m}}^3$ of distilled water at $10{}^{\circ }\mathrm{C}$ with a measuring cylinder and pour it into a beaker.
2. Add $40\mathrm{g}$ of salt and stir with a glass rod for 2 minutes.
3. Observe the solubility of the salt.
4. Repeat steps 1–3 using distilled water heated to $30{}^{\circ }\mathrm{C}$ and $80{}^{\circ }\mathrm{C}$.
5. Record the observations for all three temperatures in a table.

Data interpretation and conclusion: The observations identify the temperature at which all the salt dissolves. The conclusion states the experimental findings and whether the hypothesis is accepted or rejected.