Here is a that shows how students and I debrief each of the labs. Many reactions happen in solutions. When you mix the water and salt together, you want to make sure that you dissolve as much salt as possible to get a more accurate result to actual result. Colligative Properties of Solutions A 1. Allow the vial to cool slowly it will be necessary to construct a cold water bath in a small beaker to accelerate the process in some cases. You will record what happens in one-minute intervals, being careful not to jostle the cups. Place the beaker on a ring stand above a gas burner and begin heating the water to just below boiling.
For most substances increasing temperature will increase solubility - more solute will be able to dissolve in the same volume of solvent. Had the hot plate been working properly, we would have obtained a better amount of salt solution to put in the evaporating dish. Most of these systems will require heating before the solute will completely dissolve. Temperature, surface area, and possibly concentration were fairly easily observed. Lastly we will discuss the importance of the results that we got and the results that others got when they conducted the experiment. Our other result that we got was 95. This warm-up activity should also give students time to think a little bit about solutions and the vocabulary used to describe them.
Be sure to include descriptions of the intramolecular solvent solute and intermolecular forces involved. At this point in the lesson I project my answer key to the second part of the Solubility Notecatcher, giving students the chance to volunteer and record answers. Heat the solution until the solid completely dissolves. This is an important part of the lesson--students use the vocabulary during the rest of the lesson. Depending on the temperature assigned, heat or cool down the water to a temperature about 10 degrees lower or higher than the assigned temperature. This would have also changed the outcome for the solubility of salt.
In the second lab, you will be doing a few things. Get a 125 mL Erlenmeyer flask, add in the unknown salt sample and 40 mL of distilled water. Print out the lab : Overview: A key factor affecting the solubility of a substance - how much solute can be dissolved in a solvent - is temperature. While the solution is cooling down, check to see if the salt starts to crystallize. I note that we do not observe these empty spaces at the macroscale because they are too small. Weigh the dish and salt solution. Heat the water and salt slowly near boiling or until the salt has dissolved.
I use this time to take care of administrative tasks such as taking attendance, and to check-in with students who may have been absent. Using the hot water bath, carefully evaporate the solution. This is the solubility of the substance at that temperature - the maximum amount of solute that can be dissolved in 100. Will all of the salt dissolve? If not, how much salt will be left over? Repeat as necessary to obtain a reproducible temperature measurement. We will then talk about the results of the experiment which include the calculations and the raw data table and chart.
I explain that chemical composition is not obvious from simple observation. I compliment team work, adherence to the procedures, and I stop class if there is a safety violation or common confusion about a procedure. Be sure to add values on both the X- and Y-axes. When you transfer the salt solution to the evaporating dish, you want to make sure to not get any solid salt in the dish. Get a 400 mL beaker and fill it up halfway with water. Put the thermometer in the solution in the flask and softly stir the flask. When we were heating our salt solution, we had to heat it up to about 10 degrees more than our assigned temperature of 20 degrees Celsius.
Always be watchful of the wires whenever you reposition the apparatus! Then try a second order polynomial trendline analysis. Edited by the Anoka-Ramsey Community College Chemistry Dept. A student is trying to dissolve 3. We also forgot to weigh the evaporating dish and salt solution after we dried the salt solution the first time we had to weigh it. If you end up with too much salt left over in your solution, you might end up with not enough to salt solution and not an accurate amount of salt solution. The theory behind this experiment is to see how much of a substance, in this case potassium chloride, can be dissolved into another substance, such as water.
The following materials are required to do these labs: Materials Mini-lab 1: 3 cups or 250 ml beakers 100 ml of hot water, room temperature water, and ice water food coloring 3 different colors Mini-lab 2: Mini-lab 2: 25 grams of sodium chloride NaCl A 100 ml graduated cylinder An electronic balance 50 ml of water Stirring rod Mini-lab 3: 1 Alka-Seltzer tablet 1 electronic balance Mortar and pestle Graduated cylinder 2 100 ml beakers Mini-lab 4: 15 grams of calcium carbonate 15 g of baking soda 15 g of magnesium sulfate mortar and pestle 100 ml graduated cylinder 250 ml beaker Students work alone by reading an excerpt from a text similar to with the goal of recording some key vocabulary and definitions related to solutions. While this is heating continue with Step 2. Note and record the equation and correlation coefficient R 2 for each trendline. Another person that did the same experiment as us had 49. Note that the bottom of the vial must be close to the bottom of the water bath for the magnetic stirrer to work. Next, the materials and methods that we used for the experiment will be discussed.
Be prepared to act quickly for test tube 4 - crystallization may occur very soon after you remove the test tube from the hot water bath. Record the temperature as soon as you see crystals forming within the test tube you will need to wait awhile for crystals to form in this first test tube. Record solubility on the data sheet and turn into the instructor. Weight of dish and dry salt: 50. As the solution is cooled, a second cool hotplate or stir plate is used to stir the mixture.
Insert the temperature probe into the vial, making sure that the probe is clean and dry. Solubility of a Salt Introduction Solubility is defined to be the maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature. A discrepant event occurs for many students when they discover that adding a certain volume of solute does not necessarily increase the volume of the solution by a corresponding amount. If there are no crystals, get more salt and repeat the solution process. Will all of the salt dissolve? For many solutes, increasing the temperature increases the solubility, that is, more of the solute dissolves in the same amount of solvent. Last update was April, 2011. Follow the guidelines for Laboratory Reports at.