Summary of The Scientific Method and Experimental Design

The Scientific Method & Experimental Design Guide for Students

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Introduction

This study material explains how to design and run an experimental investigation. We use a simple, familiar example: testing whether coffee powder dissolves faster in hot water or cold water. The focus is on planning, controlling variables, setting up a control, collecting reliable observations and writing clear conclusions.

What is an experimental investigation?

An experimental investigation is a planned procedure where you change one factor to see its effect on another while keeping other factors constant.

Key parts of an investigation

  • Aim: What you want to determine. Example: To determine if coffee powder dissolves faster in hot or cold water.
  • Variables: What changes, what is measured, and what must be kept the same.
  • Control: A comparison setup where the independent variable is omitted or set to a standard value.
  • Procedure: Step-by-step actions to collect data.
  • Conclusion: What the data shows about the aim.

Break down of variables

Independent variable

  • Temperature of the water (°C). This is the factor you deliberately change (e.g., $5^\circ$C, $20^\circ$C, $60^\circ$C, $90^\circ$C).

Dependent variable

  • Time taken for the coffee powder to dissolve (seconds). This is what you measure in each trial.

Controlled / Fixed variables (use VAA to explain control)

Use VAA to state HOW each variable is controlled.

  1. Variable: Amount (weight) of coffee powder.

    • Amount: Use a consistent mass, for example 2.0 g of coffee powder for every trial.
    • Apparatus: Use an electronic balance that reads to at least 0.1 g to weigh 2.0 g for each beaker.
    • Action: Weigh each portion on the balance and place into the beaker before adding water.

  2. Variable: Volume of water.

    • Amount: Use the same volume, for example 100 ml of water for every trial.
    • Apparatus: Use a 100 ml graduated cylinder or measuring beaker to pour exactly 100 ml into each container.
    • Action: Measure and record 100 ml for each trial.

  3. Variable: Stirring (if you decide to stir or not).

    • Amount: Decide on a fixed procedure, for example 10 clockwise stirs at 1 stir per second.
    • Apparatus: Use the same stirring rod for every trial and a stopwatch to time the stirring.
    • Action: Start the stopwatch and perform exactly 10 stirs at the same speed for each trial.

  4. Variable: Type of coffee powder.

    • Amount: Use the same brand and batch of coffee powder for all trials.
    • Apparatus: Keep the coffee container closed when not in use to avoid contamination.
    • Action: Label the container and record the brand and batch in your notes.

  5. Variable: Container shape and size (if relevant).

    • Amount: Use the same type of beaker, for example 250 ml glass beakers, for every trial.
    • Apparatus: Use identical beakers available in the lab.
    • Action: Use the same beaker set for all temperatures.

Note: Only include controls that directly affect how quickly the powder dissolves. Avoid controlling irrelevant factors such as room temperature unless it directly affects results.

The control setup

  • A control is a setup where the independent variable is omitted or held at a standard value. For this experiment, a reasonable control could be a trial at room temperature (e.g., $20^\circ$C) so you can compare “hot” and “cold” results against a baseline.

Definition: A control is an experiment or trial in which the independent variable is not changed so that it can be used as a comparison.

Example procedure (step-by-step)

  1. Label three beakers: Cold, Room, Hot.
  2. Measure 100 ml of water into each beaker using a graduated cylinder.
  3. Set water temperatures: Cold $5^\circ$C (use ice bath), Room $20^\circ$C, Hot $80^\circ$C (use a kettle and thermometer).
  4. Weigh 2.0 g of coffee powder for each trial on the electronic balance and place into separate small dishes.
  5. Prepare a stopwatch and the stirring rod. Decide on stirring method: either no stirring or fixed stirring (e
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Coffee Dissolving Investigation

Klíčové pojmy: Aim: determine if coffee dissolves faster in hot or cold water, Independent variable: water temperature (°C), Dependent variable: time to dissolve (s), Control variables using VAA: specify Variable, Amount, Apparatus, Control example: room temperature trial as baseline, Use at least three repeats per condition and average results, Record identical mass and volume: e.g., 2.0 g coffee, 100 ml water, Use consistent stirring method (e.g., 10 stirs at 1/s), Measure and maintain temperature before each trial, Analyse trends and discuss sources of error, Improvements: better insulation, mechanical stirring, more trials, Conclude using data and state limitations

## Introduction This study material explains how to design and run an experimental investigation. We use a simple, familiar example: testing whether coffee powder dissolves faster in hot water or cold water. The focus is on planning, controlling variables, setting up a control, collecting reliable observations and writing clear conclusions. ## What is an experimental investigation? > An experimental investigation is a planned procedure where you change one factor to see its effect on another while keeping other factors constant. ### Key parts of an investigation - **Aim**: What you want to determine. Example: To determine if coffee powder dissolves faster in hot or cold water. - **Variables**: What changes, what is measured, and what must be kept the same. - **Control**: A comparison setup where the independent variable is omitted or set to a standard value. - **Procedure**: Step-by-step actions to collect data. - **Conclusion**: What the data shows about the aim. ## Break down of variables ### Independent variable - Temperature of the water (°C). This is the factor you deliberately change (e.g., $5^\circ$C, $20^\circ$C, $60^\circ$C, $90^\circ$C). ### Dependent variable - Time taken for the coffee powder to dissolve (seconds). This is what you measure in each trial. ### Controlled / Fixed variables (use VAA to explain control) Use VAA to state HOW each variable is controlled. 1. Variable: Amount (weight) of coffee powder. - Amount: Use a consistent mass, for example 2.0 g of coffee powder for every trial. - Apparatus: Use an electronic balance that reads to at least 0.1 g to weigh 2.0 g for each beaker. - Action: Weigh each portion on the balance and place into the beaker before adding water. 2. Variable: Volume of water. - Amount: Use the same volume, for example 100 ml of water for every trial. - Apparatus: Use a 100 ml graduated cylinder or measuring beaker to pour exactly 100 ml into each container. - Action: Measure and record 100 ml for each trial. 3. Variable: Stirring (if you decide to stir or not). - Amount: Decide on a fixed procedure, for example 10 clockwise stirs at 1 stir per second. - Apparatus: Use the same stirring rod for every trial and a stopwatch to time the stirring. - Action: Start the stopwatch and perform exactly 10 stirs at the same speed for each trial. 4. Variable: Type of coffee powder. - Amount: Use the same brand and batch of coffee powder for all trials. - Apparatus: Keep the coffee container closed when not in use to avoid contamination. - Action: Label the container and record the brand and batch in your notes. 5. Variable: Container shape and size (if relevant). - Amount: Use the same type of beaker, for example 250 ml glass beakers, for every trial. - Apparatus: Use identical beakers available in the lab. - Action: Use the same beaker set for all temperatures. Note: Only include controls that directly affect how quickly the powder dissolves. Avoid controlling irrelevant factors such as room temperature unless it directly affects results. ## The control setup - A control is a setup where the independent variable is omitted or held at a standard value. For this experiment, a reasonable control could be a trial at room temperature (e.g., $20^\circ$C) so you can compare “hot” and “cold” results against a baseline. > Definition: A control is an experiment or trial in which the independent variable is not changed so that it can be used as a comparison. ## Example procedure (step-by-step) 1. Label three beakers: Cold, Room, Hot. 2. Measure 100 ml of water into each beaker using a graduated cylinder. 3. Set water temperatures: Cold $5^\circ$C (use ice bath), Room $20^\circ$C, Hot $80^\circ$C (use a kettle and thermometer). 4. Weigh 2.0 g of coffee powder for each trial on the electronic balance and place into separate small dishes. 5. Prepare a stopwatch and the stirring rod. Decide on stirring method: either no stirring or fixed stirring (e