Last week we did an experiment to practice identifying and using the different parts of scientific investigations. We talked more about testable questions (something that can be tested through a fair experiment and the results of which can be measured). Our testable question was "Which brand of paper towels is most absorbent?" This is a testable question because we were able to design an experiment to test it AND the results could be measured (how much water each towel absorbed). We tested 3 different brands- Kirkland (Costco), Sparkle, and Seedling. Since these brands were what was being tested, the paper towel brand was our "I"NDEPENDENT VARIABLE- the thing "I", the scientist, manipulated. The independent variable is the cause (which one causes more water to be absorbed) and what is being tested. The thing we were measuring is the dependent (or responding) variable. In this case, we are measuring how much water is absorbed, so that is our dependent variable. Depending on the brand of paper towel, a certain amount of was absorbed. The dependent variable is the effect. The brand of paper towels (cause) affect the amount of water absorbed (the effect). We also had to figure out what aspects of the experiments we should keep constant. Constants are what we keep the same in an experiment. They are important because we need to be able to say with certainty that it is the independent variable changing the dependent variable. In this experiment, we had to cut the Seedling paper towels to make them the same size as the other two brands, otherwise this wouldn't have been a fair test as the Seedling towels were bigger. If we'd left the Seedling towels bigger, we wouldn't have been able to prove why they absorbed the amount they did- would it have been due to size or the brand itself? Other constants: We used the same amount of water in each experiment- 200mL. We also folded each paper towel the same way in case the shape had any impact on the results. Time: We left the towels submerged for one minute each. On their lab sheets, students were asked to come up with a hypothesis. A hypothesis is an if, then statement that tells what the scientist thinks will happen in the experiment. It is structured like this: If (independent variable/cause), then (dependent variable/effect). For example: If I soak three brands of paper towels in 200 mL of water for one minute, then Kirkland will absorb the most water. Notice how the "If" part of the hypothesis mentions the part the scientist has decided to change and is testing (we are testing the brands of paper towels), otherwise known as the independent variable. The "Then" part of the hypothesis said what we thought the measurable result would be (the dependent variable-the amount of water absorbed). We then conducted the experiment. After we had completed it, we came together as scientists and shared our findings. We learned how to calculate the mean, or average, for each brand to see about how much each brand absorbed. We discovered that Kirkland paper towels were the most absorbent of the three brands tested. In order to finish our experiment, we had to graph our data and write our conclusions. A conclusion should reference the original hypothesis and state whether it was correct or incorrect. It should also summarize the findings of the experiment. For example, for those who thought Kirkland was the most absorbent, the conclusion would have been like this: Our hypothesis that Kirkland paper towels would be the most absorbent was correct. In our experiment, they absorbed approximately 43mL on average compared to 27mL and 34mL of the other two brands. The least absorbent brand was Seedling (27mL), and second most absorbent was Sparkle (mL). You'll notice that all of our findings are measured in metric units. This is because only three countries in the entire world use US Customary (also known as Imperial) measurement- the USA, Liberia, and Myanmar. As a result, scientists all over the world relay their findings in the most commonly used form of measurement- metric. This makes it easier for people to share their results so others will understand them. Metric measurement is also a lot more precise so we can be more exact.
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