A.7. Conclusion


A scientific conclusion or explanation to an experiment goes beyond the findings of the experiment to explain the value of the experiment and returns to answer the Real-World Question. Does the experiment expand our knowledge or does it tell us to consider one of our alternative hypotheses?


Step 7. Scientific Conclusion: Today we will complete step 7 of the scientific method so we can answer why freshwater freezes before saltwater.

A. Review the scientific question, testable question and hypothesis. Starting with the hypothesis use the evidence from your experiment to support a conclusion for all three. You should have 3 small paragraphs and one final model that shows why freshwater freezes before saltwater. (You will answer these below, not here).

Scientific Question: Why does freshwater freeze before saltwater?

Testable Question: Does salt affect the temperature at which water molecules freeze?

Hypothesis: Dissolved salt will lower the temperature at which water freezes.


1. Address the Hypothesis by restating what the data tells us: Example phrases to use: “in our experiment the temperature of water with salt in it…” “yet our control experiment shows that water normally melts at....” ”This evidence proves that salt …….” "We conclude that the hypothesis is supported: Salt lowers the freezing point of water.


2. Is the data reliable (and therefore your conclusion)? A science experiment is reliable when everyone following the same experimental procedures gets the same results. For this reason, all you have to do is talk to other groups. Find out how many groups got the same results. If a group didn’t get the same results, find out if they followed the experiment correctly. Or if three groups got almost the exact same results as your team, then you can say that your experiment is reliable and therefore the conclusion is supported by this experiment and its procedures. Based on the evidence of other groups’ results, provide evidence to support whether or not your experimental results (in question 1) are reliable.



3. Address the Testable Question: Does salt affect the temperature at which water molecules freeze? Answer this question in no more than 2 sentences. But technically it should be one simple sentence.


4. Notice that you cannot answer “by how much” the salt affects the temperature at which water molecules freeze. See if you can figure out how you would need to “run” the experiment to find out “by how much” the salt affects the freezing point of water. Clarification: How would you run an experiment to find out the freezing point of saltwater?



5. Address the Scientific Question: Why does freshwater freeze before saltwater? Based on all your research and the conclusion of this experiment, explain why freshwater freezes before saltwater. Explain what is happening at the molecular level and draw a step by step diagram that supports your explanation below.



7. Diagram: Why does freshwater freeze before saltwater?