Solubility and Temperature

Name: Date: Student Exploration: Solubility and Temperature Vocabulary: concentration, dissolve, homogeneous mixture, solubility, solubility curve, solute, solution, solvent Prior Knowledge Questions (Do these BEFORE using the Gizmo.) What happens when you stir a spoonful of sugar into hot water? The sugar dissolves in the water to form a solution. Does sugar dissolve more easily in hot water or cold water? The sugar dissolves more easily in hot water than in cold water. Gizmo Warm-up A solution generally consists of two parts, a solute that is dissolved and a solvent that the solute is dissolved into. For example, sugar is a solute that is dissolved into the solvent water. In the Solubility and Temperature Gizmo, you will study how temperature affects how much solute will dissolve in a solution. To begin, check that Potassium nitrate is selected and the Temp. of the water is 20 °C. Click OK. In this solution, what is the solute? Potassium nitrate. What is the solvent? Water. Click Add 10 g to mix 10 g of potassium nitrate into the water. Did all of the potassium nitrate dissolve? Yes How can you tell? There is a resulting solution with no residue. Activity A: Solubility Get the Gizmo ready: Click reset Check that the Temp. is 20 °C and that Potassium nitrate is selected. Question: How do we find how much solute can be dissolved in a solvent? Observe: Click OK. Click Add 20 g, and observe the potassium nitrate being mixed into the solution. On the right, select the BAR CHART tab and turn on Show numerical value. The bars show how much solute has been added and how much has piled up on the bottom. Did all of the solute dissolve? Yes. Calculate: The concentration of a solution is equal to the mass of solute divided by the volume of solvent. Units of concentration are grams per 100 milliliters (g/100 mL, or g/dL). Since we added 20 g of potassium nitrate to 100 ml of water, the concentration is calculated by: What is the concentration of this solution? 20 g/100mL Experiment: Click Add 20 g again Did all of the solute dissolve? Explain how you can tell. Not all the solute dissolved. There are some residues at the bottom of the flask. The bar chart also shows 9.35 g of potassium nitrate at the bottom. Based on the amount of solute added and the amount piled up on the bottom, how many grams of solute dissolved in the water? 40 g-9.35 g=30.65 g dissolved The solubility of the solution is equal to the maximum concentration of the solute. What is the solubility of potassium nitrate in 20 °C water? 30.65 g/100mL. Experiment: Click Reset, and select Sodium chloride. With the Temp. still set to 20 °C, click OK. Add sodium chloride to the beaker until it starts piling up at the bottom. How much sodium chloride did you add? 40 g