teaching experimental design

Teaching experimental designYear 7 Integrated Curriculum

What is an “experiment”?

• In school, “experiment” is often used to describe hands-on experiences

What actually is an “experiment”?• A science experiment tests a

hypothesis

Components of an experiment• Background research• Aim• Hypothesis• Equipment• Types of variables• Results• Discussion• Conclusion

Background research

• Every experiment starts with a topic of interest (Eg. What are the effects of ocean acidification on living things?)

• Background research finds out what we already know about the topic

Aim

• Always starts with “To”• Tells the reader what the

experiment aims to do• Eg. To find out how

ocean acidification affects the shells of living things

Hypothesis

• A prediction of the results based on the background research

• Example – The more acidic the ocean is, the quicker the shells of ocean invertebrates will dissolve

If A happens then B will happen

Equipment and Method

• List the equipment used in the experiment

• Method lists how to do the experiment in steps

• Always starts with a verb• Accompanied by a

scientific diagram where appropriate

Types of variables

• Independent variable – What we change on purpose (Eg. how acidic the water is)

• Dependent variable – What we measure as the result (Eg. How much shells have dissolved after 3 days)

• Controlled variables – What we keep the same to keep the experiment fair (Eg. The amount of acids and water; the type of shell; the temperature of the environment)

• In most experiments there is ONE independent variable, ONE dependent variable and many controlled variables

Types of variables - Strategies• Cows Moo Softly

– Change one thing– Measure one thing– Keep everything else the same

Controlled variables vs control

3M HCl with shell

2M HCl with shell

1M HCl with shell

Water with shell

•Independent variable - concentration of acid•Dependent variable – how much each shell dissolves•Controlled variables – time of experiment, amount of acid and water, type of shell•Control – the water with shell

Validity and reliability

• Validity – Is the experiment testing what you intend to test?

• Reliability – Are these results a fluke? If I repeated the experiment again, will I get the same results?

Replication

• You shouldn’t just have one beaker of 3M acid, one beaker of 2M acid, etc.

• You need 5 beakers of each acid so that there is replication.

• Replication increases reliability.

• You’ll need to use average calculations.

Results

• A table and graph must be done

• A graph shows patterns that cannot be seen easily in a table

• It’s usually a choice between a column graph or a line graph

• X-axis = independent variable

• Y-axis = dependent variable

Discussion – analysis of results• What do the results mean?• Are the results expected? Are

there any usual results?• What were some possible

sources error?• How can the experiment be

improved?• What are some other

experiments to do in the future?

Conclusion

• The aim written in past tense and says whether the hypothesis is correct

• Eg. The effects of ocean acidification on shells were determined. The more acidic the water, the faster shells dissolve. The hypothesis was correct.