The Scientific Method

The Scientific Method is the method we use to make sure that no matter where you are on Earth (or the Universe) you will get the same reliable, repeatable results. Simply mixing two chemicals together or hitting something really hard isn’t exactly Science, there is much more to it. Below are some of the key words you will need to ensure your understanding.

Task: Read the terms below and simplify them into your own words to use as a quick reference. Then attempt to answer the questions to ensure your understanding.

Variable

  • A factor you can change in an experiment.
  • Eg. If you investigate what variables affect how high a ball bounces the variables include height of drop, type of ball, size, how hard you bounce it,

Independent variable

  • The ONE variable you choose to change
  • You can only change one in order to make your experiment a fair test.
  • Eg. You might choose to change the type of ball

Dependent Variable

  • The variable you measure to find out the answer to your question
  • Eg the height the ball bounces

Controlled Variables

  • The variables that are kept the same to make your experiment a fair test
  • Eg. You would need to keep the height of bounce and the force you bounce it with the same

Control

  • An experiment used for comparison. Some experiments don’t have a control.
  • Eg if you were trying out a new pain killer the control group would be people who didn’t get any medicine. If you were trying out a new food for chickens, the control chickens would be the ones who continued to get their original food

Reliable

  • Repetition repetition repetition! The more you repeat an experiment the more reliable your results are, as any odd results will stand out and you can find an average.
  • It also includes the RANGE or number of experiments you do. Eg if you only test 2 types of ball your conclusions may not be very reliable

Valid

  • Did you answer the aim you were set?
  • Were your results trustworthy?
  • Did you control all the variables apart from the one you chose to change? (the independent variable)
  • Did you use the equipment accurately?
  • Did you follow the method precisely?
  • Did you use equipment that was correct for the experiment. Eg measuring cylinder for measuring volume etc

Check your understanding of the terms

  • Why can you only change one variable at a time?
  • What should you do to make sure that your results in an experiment are reliable?
  • What is another word for “Valid”

Experimental write up

The experimental write up, more formally known as a “Scientific report” is used to record our findings so that people can at a glance understand what was done in the experiment OR read in detail if they want to know more about the experiment.

The terms below are common in Scientific reports

1.     The Aim.

  • What are you trying to find out?
  • Link the independent variable (the one you choose to change) and the dependent variable clearly (the one you measure to find out what happens).
  •  Eg. To find out how height of drop changes how high a ball will bounce?

2.     The Hypothesis.

  • What you think will happen in your experiment, a prediction
  • Make sure you clearly link the independent and dependent variable.
  • A good way to lay it out is to use the sentence. ‘If the ______________________ is increased then the __________________________ will increase/decrease.
    Eg. If the height the ball is dropped from is increased then the height of the bounce will increase.

3.     Method.

  • How you carry out your experiment.
  • Use numbered steps or bullet points
  • Write it as a series of instructions, like in a recipe book. Never say ‘I did this’ or ‘She did that”.
  • Draw a diagram with pencil and ruler showing how the equipment is put together, and label it. Make sure it is big enough to see clearly – but not huge!!!

4.     Results.

  • These are usually put in a table.
  • Draw the table with a ruler – all around the outside too!
  • You usually only need to include two columns – the independent variable (the one you change) is in the first column, and the dependent variable the one you measure to find out what happens) goes in the second column.
  • Remember to include the units that are used to measure each variable in the heading, and not when you write the answers down.

5.     Graph.

  • Choose whether you should draw a line or column graph.
  • Put the independent variable along the bottom or horizontal, x axis, and the dependent variable up the side or the vertical y axis.
  • Put the numbers on the axes so they go in equal jumps a (called a linear scale)
  • Label both axes
  • Write a title that is similar to your aim, and shows what you changed and what you measured.
  • For a line graph you can either join the points up dot to dot with a ruler or draw a line of best fit. That means you look for the best shape you can, like a straight line or a smooth curve.

6.     Discussion

  • Were there any problems with your experiment?
  • Were your results reliable (would you get similar results again? Did you repeat them?)
  • Was your experiment valid? (did you answer the question you set? Did you control all the variables and make it a fair test?)
  • What improvements could you make?

7.     Conclusion.

  • What did you find out?
  • Was your hypothesis correct?
  • Quote some actual results from your experiment to back up what you say.
  • If you can, explain why this happens as scientifically as you can.

Task: Using the equipment in your bag or pencil case to try and come up with an experiment using the headings above