Mystery Powder Lab Questions
- Explain the difference between a chemical and physical change.
A chemical change is a change in matter that happens when substances combine to create new substances that were not there before. A chemical change can usually be identified by a the substance having new colour, giving off light or heat that wasn’t there, the forming of bubbles or gas, solids changing to a liquid, or by testing how hard the change is to reverse. A physical change is a change in appearance but unlike the chemical change, no new substances are formed. For example, ice melting is a physical change because even though a solid became a liquid, no new substances formed.
- For unknown D, explain the results of each test, including what you saw and whether what you saw was a chemical or physical change.
Me and my group did six different tests on seven powders. We did a test on appearance, whether it dissolved in water, what happened when heated, and what happened when it came into contact with universal indicator, an iodine solution, and vinegar. For unknown powder D the appearance was powdery with small clumps, it was a dirty white colour and was matte. It stuck to walls like unknown C but not quite as much. The next test we conducted was whether or not the powders dissolved in water. Unknown D did not although it became thicker and pasty. The change here was physical because no know substances were created. The third test was what happened to the powder when heated. Powder D stayed the same as did the rest of the powders except for E and Z. The change in powder D was neither physical nor chemical as there was no change. We then tested what would happen when it came into contact with universal indicator. When the eye dropper’s drops of universal indicator hit powder D, it solidified and turned yellow which is a chemical change because a new substance formed. We know this because a liquid turned into a solid with no heat taken away and no pressure added. The next test was what happened when the powders came into contact with the iodine solution. When the iodine hit unknown powder D, the iodine turned brown and stayed a liquid although it didn’t mix in with the powder. This was a physical change as iodine is already a shade of brown so not much changed. The last test we performed on the unknown powders was what happened to them when they came in contact with vinegar. The vinegar-powder mix became sticky where the vinegar hit unknown D and the vinegar became a solid. This change was chemical as the liquid vinegar became a solid without change in temperature or pressure and it became a sticky substance which was not there before.
- Based on your results identify which two powders make up Mystery Powder X and which two powders make up Mystery Powder Z?
Based on our test results, we think that unknown powders C and E made up mystery X, and that A and D made mystery Z. C and E make X because of certain changes in each of them that only happened in either C and X or E and X. For example, when C came into contact with the universal indicator it solidified. When E did, it turned green and X solidified and turned green. Also when the vinegar was dropped onto the powders, the only two that bubbled up were E and X, although X not as much which makes sense because it must have been diluted with C. This is why X is made up of C and E. As for Z there are only three left. We know that one of them is powder D because Z is powdery and the only two that are powdery are C and D which C has already been used. Also D and Z are the only two powders that solidified and turned yellow when they came into contact with universal indicator. As for the other powder that makes up Z it can only be either A or B. This one was a little more difficult to decide on which one was in Z because not as many properties shared. My conclusion was that it was A in Z because of some small similarities. For example, Z is a powder but A and B are both crystals. However, A has smaller crystals and B’s crystals would probably be evident in Z. Another reason is that when tested with universal indicator, Z becomes solid and yellow like D. B stays the same but orange, and A stays the same but a yellowy-orange. If B was in Z, Z would probably not have become yellow but more of an orange. Mystery X is C and E, and mystery Z is A and D
- Explain any experimental sources of error from this lab (where could you have possibly made a mistake?)
I think me and my group did really good and there was only two mistakes I could find. The first one was that when heating, we had to look at the bottom of the cups of powder for colour because we put a little too much in and did not have time to heat the top. The second mistake was we might’ve done something wrong when testing A because I’m not sure if the results should have been that close between A and B being in Z. I could still find that A was the one in Z but if I had the time I would have re-done the testing on A and heated the powders again with a little less in them.