Boiling Ice Lab. D) Materials A thermometer A beaker A stopwatch A hot plate Ice

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1 IP 644 Name: Date: Block: Boiling Ice Lab A) Introduction All matter can exist as a solid, liquid, or gas. The phase in which a substance exists depends on its temperature. The solid phase exists at a relative lower temperature than the liquid phase. The liquid phase exists at a lower temperature than the gaseous phase. As you know, the temperature of a substance changes when heat energy is either added to it, or taken away from it. A substance will absorb heat energy and increase its temperature, or it will lose heat and get colder. At some point, enough heat will have been added or taken away that the substance will undergo a phase change. We are going to investigate phase changes in water. Water is a great substance to use in our study for two reasons. Not only is water an extremely common substance, but also we all have experienced it in each of its three phases: gas, liquid, and solid. Phase changes in water take place at temperatures with which we can work comfortably. B) Objectives You will do an activity to answer the following two questions: 1) What will happen to the temperature when heat is added to it? 2) What will happen to the phase in which water exists as heat is added to it? D) Materials A thermometer A beaker A stopwatch A hot plate Ice E) Description You will start with a sample of ice (solid water) that you will heat over time. You will make frequent, careful measurements of the temperature of your sample. You will also observe the visual appearance of your water sample. You will record your observations, including the time intervals, in you notebook. A time interval of 1 minute is suggested.

2 E) Procedure 1) Review the safety rules. 2) Get the materials to your working station. 3) Before turning the hot plate on, measure the initial temperature of the ice and record it first in your data table. Wait for the temperature to get as low as it would go. 4) Turn the hot plate on and start the stopwatch. See board or ask teacher for temperature setting. 5) Stir the mixture continuously (this means ALL THE TIME!) and carefully with the thermometer. Make sure the thermometer doesn t touch the bottom or sides of the beaker. 6) Record the temperature on the data table every minute (don t stop the stop watch at any time, instead simply record the temperature every minute). As you record the temperature and time, record these events as they occur, under observations. a. Bubbles appear. b. Last piece of ice disappears. c. Condensation appears. d. Steam leaving the beaker. e. Water boiling vigorously. 7) Keep taking measurements until your mixture has been boiling for four minutes, or until five minutes before the end of the block. 8) Shut off the hot plate, clean you lab area, dump the water, and put all materials where you found them.

3 F) Data t (min) T ( C) Observations t (min) T ( C) Observations

4 G) Graph your data. Use graphing paper or a computer (only if you are super familiar with graphing software) to graph your data. You will represent the time in the x-axis and the temperature in the y-axis. Remember that a complete graph includes: a title, labels and units, an appropriate scale, all data points, and indications of your observations. Please remember: do not connect the dots! H) Analysis. You will write, and then type, a lab report that must include the following: A brief explanation of the lab s purpose. The purpose of the lab is to A brief description of the procedure. To test this we Background information of the physics behind temperature change and phase change. When heat is added to a substance A graph and a brief description of your data. We can see in the graph A conclusion that answers the two objective s questions. In conclusion: A bibliography (if needed) Be sure to connect all these parts properly and coherently, so it doesn t look like a bunch of sentences one after the other. Remember to: Type your report and include a title (the word conclusion will not suffice) Write your name, block, and date on all three parts. Staple all three parts together.

5 I) Interesting facts about water. (Extra credit.) Phase diagram of water: Critical point Pressure (atm) SOLID LIQUID 1 Triple point GAS Temperature ( C) Background information: The temperature at which a certain substance changes phase is determined by the atmospheric pressure (see y-axis, measured in atmospheres). The line that separates the liquid and solid phases represents melting/freezing of water; the line that separates the liquid and the gas represents the vaporization/condensation of water; and the line that separates the solid and gas phases represents the sublimation/deposition of water. At atmospheric pressure, 1 atmosphere, the boiling/condensing point of water is 100 C and the freezing/melting point of water is 0 C; this is represented by the doted horizontal line. The three solid, curved lines shown on the graph represent the three phase changes between the three phases: boiling/condensation, freezing/melting, and sublimation/deposition. The point at which the three lines meet is called the triple point; all three phases: liquid water, solid water, and vapor water coexist at this point. The point at which the boiling/condensation line ends is called the critical point. The x coordinate of this point is called the critical temperature; the y coordinate of this point is called the critical pressure. For temperatures higher than the critical temperature and pressures higher than the critical temperature, liquid and gas are no longer distinguishable, instead there is a new phase called supercritical fluid.

6 Questions (answer on a separate piece of paper, using complete sentences, and using CER) 1) If the pressure is more than 1 atmosphere, will the freezing point of water be at a higher temperature or a lower temperature? And the boiling point? Hint: draw a line parallel to the one shown above 1 atmosphere. 2) What is sublimation? What is deposition? Sublimation or deposition can only happen below what point? 3) The triple point is the point in which the three phases coexist. Find out what are the coordinates of the critical point in atmospheres and ºC. (You will need to do some research) 4) The negative slope of the melting/freezing line indicates the fact that ice is less dense than liquid water. This is the reason why ice floats in water. Life is believed to have started in water. Why is the fact the ice is less dense than liquid water so important in the staring of life on earth? Think what would happen if the opposite were true: what would happen if ice were denser than liquid water? What difference would it make?