Scientific Method
During the floating raisin experiment, a student notices bubbles attached to the raisins. Which scientific skill is being used?
Observation.
What name is given to the variable that the investigator deliberately changes?
Independent variable.
What is a hypothesis?
A testable proposed explanation or prediction based on observations or scientific ideas.
Before investigating sand and gravel, a student asks, “Which material retains more water?” What part of the scientific method is this?
Identifying the problem or asking an investigative question.
Students compare water retention in sand and gravel. What is the independent variable?
The type of material: sand or gravel.
Which is a testable hypothesis? A: “Raisins are interesting.” B: “Raisins will rise to the surface more often in Sprite than in cream soda during three minutes.”
B. It predicts an outcome that can be measured and compared.
Arrange these steps in a suitable order: draw a conclusion; test the hypothesis; identify a problem; analyse results; formulate a hypothesis.
Identify a problem → formulate a hypothesis → test it → analyse results → draw a conclusion.
In a balloon investigation comparing baking soda and flour, students measure the balloon’s circumference after two minutes. What is the dependent variable?
The balloon’s circumference after two minutes.
Improve this statement into a testable hypothesis: “Sand is better than gravel.”
Sand will retain a greater volume of water than gravel when equal amounts of each material receive the same volume of water and drain for the same time. Accept other clearly worded, testable predictions.
A student tests raisins in 100 cm³ of cream soda and 200 cm³ of Sprite. Explain why this is unfair and state one correction.
Both the type and volume of drink differ. Use the same volume of each drink so that only the type is deliberately changed.
Students count how many times raisins rise to the surface in cream soda and Sprite during three minutes. Identify the independent and dependent variables.
Independent: type of drink. Dependent: number of times the raisins rise to the surface in three minutes.
For a new version of the balloon activity, equal masses of baking soda and flour are separately mixed with equal volumes of vinegar. Write a hypothesis predicting balloon circumference after two minutes.
If baking soda is used instead of flour, then the balloon will have a larger circumference after two minutes because baking soda reacts with vinegar to release carbon dioxide.
Practice data: Equal volumes of water were added to equal amounts of sand and gravel. Sand retained 35 cm³ and gravel retained 12 cm³ after the same drainage time. State a conclusion and explain why the investigation should be repeated.
Sand retained more water than gravel under the conditions tested. Repeating checks whether results are consistent and helps identify unusual results.
A student tests sand with 100 cm³ of water for two minutes and gravel with 150 cm³ for five minutes. Identify the intended independent variable and two variables that should be controlled. Explain why.
Independent: type of material. Controlled: volume of water and drainage time. Both must be kept the same because they could affect the amount of water retained.
A student writes, “Sprite is the best drink for raisins.” Rewrite this as a testable hypothesis and identify the independent and dependent variables.
Hypothesis: Raisins will rise to the surface more often in Sprite than in cream soda during three minutes under the same conditions. Independent: type of drink. Dependent: number of rises in three minutes. Accept an opposite testable prediction; a hypothesis need not match the eventual result.