Physical Change, Chemical Change, Observations, Inferences, and
- I can make quantitative and qualitative observations about a chemical phenomenon and use both to
practice creating an evidence-based explanation.
- I can explain the difference between physical and chemical changes.
- I can use evidence and observations to explain a phenomenon
1,000 mL graduated cylinder
30% Hydrogen Peroxide (H2O2)
2 M Potassium Iodide (KI) or Sodium Iodide
Pre lab questions:
1) How is an observation different than an inference?
2) How is a qualitative observation different from a quantitative observation?
1. The first step is to put on your safety glasses.
2. Measure 100 mL of the 30% hydrogen peroxide into the graduated cylinder. It's best to place the
cylinder in a large tray to make the cleanup as easy as possible.
3. Add a squirt (about 25 mL) of dish soap to the graduated cylinder containing the 30% hydrogen
4. Add a several drops of food coloring.
5. The last step is to add 20 mL of the 2M sodium iodide (2M refers to the molarity of the solution).
Post lab questions:
 In your own words, what did you see happen throughout the phenomenon?
 In your own words, what do you think happened and why? Use evidence from #1 and any other
knowledge to support your argument.
 Be curious. Wonder and question. Don’t accept everything.
 Take risks in guessing, explaining and trying. Chemistry is new to many of you. That’s okay.
 Make as many observations as you can. Detailed. Specific. Relevant.
 Arguments must be supported with evidence using academic language and content, which we will
I think … because....; I saw.... which I think means...
Watch the video on moosclass.wordpress.com. Click on the Chemistry tab, then videos, and then
click the link to the video.
On a separate sheet of paper, answer the following two questions.
 In your own words, what did you see happen throughout the phenomenon? Provide
as many details as possible. You can re-watch a video tonight as many times as you want and even
post a comment on the website.
 In your own words, what do you think happened and why? Use evidence from #1
and any other knowledge to support your argument. Your argument should be at least 5 complete
*Be sure that you are clear about what are observations (and if they are qualitative or quantitative) and
**Optional sentence starters:
In the video I saw....... which makes me think......
I think that the water......... because..........
***BONUS: you get one bonus point if you type your response and email it to email@example.com before