Prior Knowledge Questions Do these BEFORE using the Gizmo.

Solubility and Temperature Answer Key Vocabulary: concentration, dissolve, homogeneous mixture, solubility, solubility curve, solute, solution, solvent Prior Knowledge Questions (Do these BEFORE using the Gizmo.) [Note: The purpose of these questions is to activate prior knowledge and get students thinking.Students are not expected to know the answers to the Prior Knowledge Questions.]

• What happens when you stir a spoonful of sugar into hot water?

The sugar dissolves into the water.

• When sugar or another substance is dissolved in water, it disappears from view and forms

a homogeneous mixture with the water, also called a solution.If you can’t see the sugar, how can you tell that it is there?The water tastes sweet and may appear slightly cloudy. [You can boil or evaporate the water to see solid sugar again.]

• Does sugar dissolve more easily in hot water or cold water? Hot 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?

All of the potassium nitrate disappeared as it was stirred into the water. This study source was downloaded by 100000816398418 from CourseHero.com on 06-11-2021 14:11:20 GMT -05:00

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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).What is the concentration of this solution? 20 g/100 mL (or 20 g/dL)

3. Experiment: Click Add 20 g again.

• Did all of the solute dissolve? Explain how you can tell.

No, some of the solute piled up on the bottom of the container.

• Based on the amount of solute added and the amount piled up on the bottom, how

many grams of solute dissolved in the water? 30.65 grams of solute have dissolved. C.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/100 mL

• 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? Answers will vary.
• How much sodium chloride piled up at the bottom? Answers will vary.
• How much sodium chloride dissolved in the water? 36.66 grams
• What is the solubility of sodium chloride in 20 °C water? 36.66 g/100 mL
• Apply: At 20 °C, how much sodium chloride could be dissolved into 2 L of water? 733.2 g This study source was downloaded by 100000816398418 from CourseHero.com on 06-11-2021 14:11:20 GMT -05:00

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