This homework should be submitted as a hard copy, on actual paper. I think we all need a break from the HTML stuff. At least, I know I do.
Answer one, and only one, of the following:
Even though paper clips are denser than water, you managed to get a paper clip to float on a water surface.
Explain why a mixture of detergent in water makes things clean.
In class you contacted a variety of solids with several different liquids. Sometimes the solids dissolved in the liquids, and sometimes they did not. Give an example of a solid we did not test in class, a liquid that dissolves it, and a liquid that does not dissolve it.
The mixtures of sugar, corn starch, and milk powder with water were used as examples of a solution, suspension, and colloid of a solid in a liquid. Complete the chart below, identifying the types of mixtures and the natures of the components. Also explain your reasoning for each classification you make.
| Mixture | Type | Nature of Components |
|---|---|---|
| sugar in water | solution | solid in liquid |
| corn starch in water | suspension | solid in liquid |
| milk powder in water | colloid | solid in liquid |
| dust storm | ||
| cloud or fog | ||
| humid air | ||
| spray from a waterfall | ||
| silty water | ||
| smoke | ||
| coffee |
Have you ever tried to make rock candy? The recipe is similar to what you did in the “Sugar Crystals” activity, except that you start with white sugar instead of brown sugar. Sugar is dissolved in hot water, the solution is cooled, and crystals slowly grow from the syrup.
If you try to make colored rock candy by adding food coloring to the water, the crystals will be only faintly colored, if at all. Why is this? Explain this as you would to a disappointed second-grader who was hoping to make brightly-colored rock candy.
Take your choice of these tasks. Do not submit answers to more than one of them. Just choose one, and submit it. Your answer should thoroughly address all points of the question. An adequate answer will be several paragraphs long.
Submit your answer in hard copy. Please do not submit it electronically! I think we can all use a rest from that. I plan to sit by the fire, or sit out in the sun (depending on the weather—you never know what it will do around here this time of year), reading your answers.
Warning: As always, Do not turn in paper that has ragged edges! If you write your work in a spiral-bound notebook, trim the edge before submitting it. Papers with ragged edges will be returned unmarked.
Copyright © 2006, Richard Barrans
Revised: 28 October 2009. Maintained by Richard Barrans.
URL:http://www.barransclass.com/phys1090/hw/hwk_10_mix.html