Teaching experimental design Year 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.