Summative Evaluation Practice Task

Saving Energy

Designing an Experiment

Scenario 2: Choosing a Fertilizer

Fertilizer is a mixture of chemicals that is added to soil to aid with plant growth. The addition of fertilizer allows farmers to increase crop yields in order to increase the efficiency of their labour. Most fertilizers provide soil with some combination of magnesium, calcium, phosphorus, nitrogen, sulfur and potassium. Different brands of fertilizers make different claims about plant yield and can vary greatly in price. Design an experiment to determine which brand of fertilizer optimizes plant growth.

You will be provided with the following materials:

Name: ______

  • Potting soil
  • Plant pots
  • SuperGreen® brand fertilizer
  • PlantPlus® brand fertilizer
  • SoilConditioner® brand fertilizer
  • CropYield® brand fertilizer
  • Measuring cups
  • Water

A)The Question: [1 mark]

Most investigations start with a question you are trying to answer. What question will you be investigating?

B)The Variables: [2 marks]

In many investigations you are examining how changing one factor affects another. So there is a cause and effect relationship between two factors. We refer to these factors as the independent variable and the dependent variable. For your investigation determine what factors are the independent and dependent variables.

Independent Variable (Cause) / Dependent Variable (Effect)

C)The Test Cases: [1 mark]

In most experiments you repeat the experiment many times changing one factor, or variable, each time you repeat the experiment. By doing this you can determine what effect that variable has on the outcome of the experiment. In this investigation you will repeat the experiment at least 3 times, each time with a different test case. Below list the four test cases you will be investigating:

Test Case 1
Test Case 2
Test Case 3
Test Case 4

Name: ______

D)Controlled Variables [2 marks]

What factors will you keep the same for each of the test cases? If you change more than one thing during each test case you won’t know what was responsible for the final outcome.

For example, to bake fluffier bread I added more baking powder and flour to my recipe. My bread was much fluffier but I didn’t know what accounted for this change – the extra baking powder or flour or maybe both.

List at least FOUR variables you will be controlling, or keeping constant, in each of your test cases:

E)The Experiment: [3 marks]

How are you going to test your question? What procedure will you follow in order to answer the question completely? In the space below briefly outline how you will be testing the question.

F)Making Observations: [3 marks]

Whenever you perform an investigation you make observations. In this case you should also make some measurements. What measurements will you be making and what will you be looking for as you perform the experiment? Design an observation table that could be used to record the data.