Do the same with 2 tall glasses. Observe how the water level changes in both glasses. Densities of materials will change if you change the state of the material liquid into a solid and change the temperature of the material warm vs.
With water you can see some fun science when you change the temperature and thus change its density. We find that warm water has a lower density then cold water. This is interesting because when water freezes it actually has a lower density then water. Aspirin tablets fizz when put into water. This activity brought to you in partnership with Science Buddies. Already a subscriber?
Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Key concepts Chemical reactions Molecules Carbonation Temperature Introduction Have you ever wondered why bubbles form when an Alka-Seltzer tablet is dropped into water? Build a Cooler. Get smart. Sign up for our email newsletter. Sign Up.
Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Explore Either do a demonstration or show a video to investigate whether all substances dissolve much better in hot water than in cold water. Ask students to make a prediction: In the activity, you have seen that hot water dissolves sugar better than cold water. Do you think that salt will dissolve much better in hot water than in cold, like sugar does?
If you choose to do the demonstration, follow the procedure below. Question to Investigate Will salt dissolve much better in hot water than in cold, like sugar does? Place 1 tablespoon of salt and 1 tablespoon of sugar in each of their labeled cups. At the same time, pour one tablespoon of salt into each graduated cylinder.
Compare the amounts of salt and sugar left undissolved Show students the graduated cylinders with the salt. Show students the graduated cylinders with the sugar. Expected Results Less sugar is visible in the hot water than in the cold, meaning that more sugar dissolves in the hot water than in the cold water.
Show students the table and graph for the solubility of sugar and salt at different temperatures. Table 1. Ask students: The demonstration showed that temperature affects the dissolving of sugar more than it affects the dissolving of salt.
Explain how the graph shows this. As the temperature increases, more and more sugar can be dissolved, but only slightly more salt can be dissolved. About g of sugar will dissolve. About 37 g of salt will dissolve. Extend Plot a solubility curve for potassium chloride and compare it to the solubility of sugar and salt.
Table 2. Downloads Lesson 5. Student Reading Use this related reading to extend student comprehension after completing the lesson. Measure the temperature of the water and record it in the table. Add a tablet and record the time it takes for the tablet to react. Repeat with room temperature water, then with hot water heated to 70 degrees C using a hot plate. The Effect of Surface Area on Rate of Reaction Prepare three different sizes of the Alka Seltzer tablets: A whole tablet A tablet broken into quarters A tablet ground into powder: Place the tablet it a piece of weighing paper wax or parchment paper work as well and break it either with your hands or crush it using the back of a metal spoon.
Add mL of water to a large beaker. Measure and record the temperature of the water and make sure it is consistent between trials. One student should be ready with a stopwatch and another student should be ready with the whole tablet. The student with the stopwatch should count to three and on three start the stopwatch.
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