Introduction Background Info: To start, we know that water freezes at zero degrees Celsius, or thirty two degrees Fahrenheit. We also know that when adding a substance to water changes its freezing/melting point. Using information, we figured we could create a fairly accurate hypothesis. We also know that tap water (which is the water we used as a control) is not going to be chemically exact in every cube, therefore creates an uncertainty. We came as close as we can to adding the exact amount of salt/sugar into each cube, and because we couldn’t add the right amount down to the grain, we have yet another uncertainty. Other than these small uncertainties, we believe that our experiment came as close to perfect as we could get. Review of Literature: While searching for related experiments on melting sugar water and saltwater ice cubes, I found various credible articles. One stated that a mom and her son were doing the same experiment as I am, and their results were the same as what I got. They posted their experiment on a website at which there was a reply that gave background information to help back up their results. “Here are some things to consider. (1) Salt is more dense than sugar, so that many more molecules of salt are present in the same volume (i.e., tsp) as sugar. (2) Not only that, but each molecule of salt dissociates in water into two ions, each with the ability to lower melting point, whereas each molecule of sugar dissolves without dissociating. In other words, the same number of molecules salt has twice the capacity to lower melting point as sugar.”(Morris) I used this information in comparison with my results. I also found a website where a student did a quite similar experiment and had a professor explain his results. The website included a good amount of information I used to help further my investigation. “When you dissolve salt, it changes into ions: NaCl ----> Na+ + Cl-, so for every molecule of NaCl you dissolve, you make two things in solution. This makes the solution as if there were twice as many particles, effectively. So the freezing point changes twice as much if the number of solute particles is the only important thing! Of course there are other factors involved, like the charges on the ions above, and the fact that they are atoms and not molecules...but these only affect how large the effect is, not whether it happens.” (Topper) Description of Question: The question that this lab represents is: If I add various amounts of sugar and salt individually into a constant amount of water, which solution will melt faster…The tap water? The saltwater? The sugar water? In more detail, this is asking: If sugar is dissolved into water at different percentages (by volume) of solution separated individually along with salt dissolved into water, what will be the melting times? Which solution melted the fastest? Hypotheses: (1) If I add a certain amount of sugar to a constant amount of water and freeze, then it will melt faster than tap water, and slower than saltwater. (2) If I add a certain amount of salt to a constant amount of water and freeze, then it will melt faster than tap water, and faster than sugar water. Bibliography: SEPS.org. Science Education PartnershipS. April 3. Ask A Scientist. The Materials • One 16 cube ice tray • 16 ceramic plates • One 26 oz. container of iodized salt • One approx. 5 lb bag of sugar • Tap water • Measuring cups • Measuring spoons • Freezer • Cell phone (stop watch) • Masking tape (labeling) • Thermometer The Procedure 1. Put thermometer in freezer until the temperature is known 2. Measure out one-eighth teaspoon of salt and pour into one ice cube slot 3. Repeat step 1, but add one-eighth teaspoon with each measurement. Do this for one row of the ice tray (8 ice cube slots in a row) 4. *Skip measuring out the 4 teaspoons of salt* 5. Repeat steps 1-4 using sugar 6. Add 3 teaspoons of water to each ice cube slot 7. Put in freezer 8. Wait until frozen 9. Take each cube out and place them on their own ceramic plate. 10. Label each plate as to which concentration it holds 11. Start the stop watch 12. Record time once each ice cube melts 13. Create 3 tap water cubes of 4 teaspoons 14. Repeat steps 7-12 with the tap water ice cubes The Data 8.3% 60min53sec 12.5% 52min39sec 16.6% 48min39sec 20.8% 43min56sec 25% 39min37sec Saltwater Melting Times 29% 29min04sec 33% 21min07sec 37.5% 14min08sec Percentage solution by volume Time (minutes/seconds) 8.3% 67min58sec 12.5% 59min06sec 16.6% 51min35sec 20.8% 47min15sec 25% 46min02sec Sugar water Melting Times 29% 36min26sec 33% 25min02sec 37.5% 17min01sec Percentage solution by volume Time (minutes/seconds) Tap water cube (4 tsp) 1 - 78min36sec Tap water cube (4 tsp) 2 - 75min13sec Tap water cube (4 tsp) 3 - 76min24sec The Graphs - The salt water melted in an average time of about 38 minutes whereas the sugar water melted in an average time of about 43 minutes, and the tap water in about 76 minutes The Results/Conclusion In conclusion to my experiment, it turns out that my hypotheses were correct in that saltwater does melt faster than normal tap water and sugar water, and that sugar water melts faster than normal tap water, but slower than saltwater. The tap water melted slower than both the sugar water and saltwater. Throughout this investigation, I have learned many new things. I have learned that when water freezes, it expands by one-eleventh of its original volume. I also learned that each molecule of salt dissociates in water into two ions, each with the ability to lower melting point, whereas each molecule of sugar dissolves without dissociating. The experiment went as well as I would have imagined, and I believe my results are fairly accurate and credible. In the case of uncertainty, I believe that there were some things that may have affected my data in a minor way. The temperature inside of my kitchen was not controlled, and the ice cubes were vulnerable to air current, heat waves from appliances, and the heat from the plates which were stored in a cabinet that may have had a different temperature from the rest of the room. We couldn’t get 100% of the cubes out of the ice tray, and the measurements of the salt, sugar, and water may have not been exact. When the melting times were recorded, it was by observation and the ice cubes may not have been completely melted. To improve this experiment, I would make sure that each measurement was exact, the room in which the ice cubes melted was controlled and not prone to moving air current, heat waves and heat displacement from what the cubes came in contact with. The Ice cubes would be extracted with precision, making sure not one flake of ice was left behind. Also, when the times were recorded, the ice would have been completely melted and at the exact time that they melted, rather than by observation.