VIEWS: 5 PAGES: 5 POSTED ON: 7/9/2011
ICY ROAD SALT Draft By Danny Soekarnsingh, Aram van Meurs and Pebbles Tros 10-04-2011 Introduction The subject we chose for our ICY ROAD SALT chemistry assignment is: ‘What effect does different kinds of salt, dissolved in water, have on the buoyancy of an object with the same density as the water?’ Because our object has to have the same buoyancy as the fluid its floating in (this, because when the object has the same density as the water it will steadily float in the water and its easier for us to mark the differences in the buoyancy level when we dissolved the two different kinds of salt in the water ) we cleverly chose to put an amount of water in a plastic bag which we sealed airtight so there wouldn’t be any water in to make the object more buoyant, this we used as our object. Our test includes 2 different kinds of salt dissolved in regular tap water and one control with no salt dissolved in the water, here we want to conclude what kind of affect the two different special chosen salts have on the buoyancy of the equally to the water chosen object. Besides the test with the regular tap water we will also perform the test again with the two same special chosen salts and the control but this time instead of tap water were using demineralised water to see what kind of affect that has on the object with the same density as the demineralised water, and if there are major differences in the buoyancy levels with the test with the regular tap water. -So our main goal in this test is to conclude which characteristics in the salt makes the object less or more buoyant, we did this by blocking out all the other variables such as: temperature volume, volume of the object, amount of salt. So the only differences are the characteristics of the salt. -as second goal we are going to compare the buoyancy levels of the test with the tap water and the test with the demineralised water so we can conclude if different kinds of water have a different effect on the buoyancy levels. The idea When we were thinking about a suitable experiment for the icy road salt assignment, we at first could not come up with a good experiment but after that, we read a suggestion list on the internet about possible experiments. We found an article about the Dead Sea. We thought this was a pretty interesting subject because we wanted to know why objects in the Dead Sea float, we actually knew this was because the Dead Sea has a high salt level but we wanted to know what characteristics the salt must have to make an object float more or less. Execution Used objects and substances -Weighing scale -Graduated cylinders -Sandwich bags -Spatulas -Small steel bowl -Clothespins -Tap water -Demineralised water -Sodium sulphide (Na2S) -Ammonium dichromate First, we thought about which substances would be useful in our experiment and we made sure they were available. After we did, we started with the experiment. We started by filling three of the cylinders with 150 ml of tap water and the other three cylinders with 150 ml of demineralised water. We then filled a sandwich bag with tap water and another one with demineralised water. To make sure there'd be absolutely no air in the bags, we made a knot in them whilst we held them under water. We then proceeded by putting the bags of water in their respective cylinders. The bag with tap water went in one of the cylinders containing tap water. The bag containing demineralised water went in one of the cylinders containing demineralised water. We did this, because the density of the objects (the bags of water) and the water itself had to be the same. We took pictures of the bags of water floating in the water, noted down our observations and took out the bags of water by grabbing them with the clothespins. We then continued the experiment by finding out how much ammonium dichromate was needed to completely saturate the 150 ml tap water in one of the other cylinders by adding the substance until it would no longer dissolve in the tap water. After we added 40 grams of ammonium dichromate, it would no longer dissolve in the tap water, meaning the tap water was saturated. We then also filled one of the cylinders with 150 ml of demineralised water with 40 grams of ammonium dichromate and we filled the last two cylinders, one with tap water and one with demineralised water, with 40 grams of sodium sulphide. We made absolutely sure we dissolved as much of the substances as we possibly could. The sodium sulphide didn't seem to dissolve in the water a lot at all at first, but after a while, it turned out it dissolved better than we thought it would. Once again, we put the bags of water in their respective cylinders, but these were filled with mixtures of water and sodium sulphide or ammonium dichromate. We once again took pictures of the bags in the mixtures and we noted down our observations. Every time we removed one of the bags from the mixtures, we made sure we'd clean the outside of the bags the best we could, so the bags wouldn't have any of the previous mixture on them. If they did, it could have caused us to note down inaccurate results. Results Experiment using tap water and a small bag of tap water Small bag of tap water: 25,4 grams = 25,4 ml Volume of tap water used in cylinder: 150 ml (Control) Experiment 1 We put the small bag with 25,4 ml tap water in the cylinder with 150 ml tap water and yes, the volume increased from 150 ml to 150 + 25,4 = 175,4 ml. The bag of water floated exactly underneath the surface of the water. This proves the theory about buoyancy concerning an object of the same density as the fluid in which it is placed (we ignore the density effects of the bag, besides, our previous results proves that it was valid to do so). Experiment 2: tap water and ammonium dichromate (and saturation check) Salt addition: ammonium dichromate (NH4)2Cr2O7 We needed to find out experimentally how much salt is needed to make a saturated solution. Also, during this same procedure, we tested the buoyancy of the bag of tap water in this solution. We have listed our results in a table: Salt addition (NH4)2Cr2O7 With bag of tap water in it, the volume rose to: 10 grams 150 ml 181 ml added 15 grams makes 25 grams 181 ml 183 ml added 15 grams makes 40 grams 183 ml 192 ml Without the bag of tap water in it and with 40 grams salt in the water, the volume of the cylinder was: from 150 ml 164 ml. When having added 40 grams of salt, the water seemed saturated (not quite all of the last 15 grams of salt was dissolved). For this reason we used 40 grams of salt in the remaining experiments. Experiment 3: tap water and sodium sulphide Salt addition: sodium sulphide Na2S We filled a cylinder with 150 ml of water. We added 40 grams of Na2S. The Na2S really stunk! It took quite a while to dissolve and we had to stir for a long time, because there were really big chunks of salt. Without the bag of tap water in it and with 40 grams salt in the water, the volume of the cylinder was: from 150 ml 166 ml. Upon insertion of the bag of tap water, the water level rose to 195 ml. Experiment using demi-water and a small bag of demi-water Small bag of tap water: 38,9 grams = 38,9 ml Volume of tap water used in cylinder: 150 ml Experiment 4: demi-water and ammonium dichromate Salt addition: ammonium dichromate (NH4)2Cr2O7 We added 40 grams of (NH4)2Cr2O7 to a 150 ml of demi-water in a cylinder. Without the bag of tap water in it and with 40 grams salt in the water, the volume of the cylinder was: from 150 ml 165 ml. Upon insertion of the bag of tap water, the water level rose to 200 ml. Experiment 5: demi-water and sodium sulphide Salt addition: sodium sulphide Na2S We added 40 grams of Na2S to a 150 ml of demi-water in a cylinder. Without the bag of tap water in it and with 40 grams salt in the water, the volume of the cylinder was: from 150 ml 166 ml. Upon insertion of the bag of tap water, the water level rose to 207 ml.
"ICY ROAD SALT"