HW for 3/24

1) HW #10 pg. 565 ex 16.2, pg. 572 #1-6
2) All late HW due Thurs 3/26
3) Test on Thursday
4) Composition books due—8 take home labs, mixture stations, kool aid, salt/boiling, polluted water

Take Home Lab #8

Take Home Lab #8: Solubility Lab

Question: Which household substances are polar and which are nonpolar?

Safety: Keep the cups out of reach of children so they do not drink the solutions. Do not consume any of the materials. Use caution when working with rubbing alcohol; it is flammable. Keep away from all flames and/or spark sources. Immediately wipe up any liquid spilled on the floor.

Materials: cups, oil, water, rubbing alcohol, salt, sugar, baking soda

Procedure: In this lab, you will figure out which solids are soluble in which liquids. For the liquids, you will use water, rubbing alcohol, and cooking oil. For the solids, you will use salt, sugar, and baking soda. In the end, you will see if the liquids will mix together. This will help you answer the questions about which solutes are solvents are polar.

            In a small cup, try the following combinations to see if the solute will dissolve in the solvent. Stir the solutions and allow at least 60 seconds for the solutes to dissolve. Be sure to clean the cups with dishwashing liquid between each use.

            1. water and salt

            2. water and sugar

            3. water and baking soda

            4. rubbing alcohol and salt

            5. rubbing alcohol and sugar

            6. rubbing alcohol and baking soda

            7. cooking oil and salt

            8. cooking oil and sugar

            9. cooking oil and baking soda

            10. cooking oil and water

Post-Lab Questions:

1. Make a chart showing whether each substance dissolved or not. Or mixed or not.

2. In general, polar items dissolve other polar items and nonpolar items dissolve nonpolar items. Water is polar. Which of the solids are polar?

3. In general, polar liquids mix with other polar liquids, and vice versa. Which of the liquids are polar?

4. From your experience, is antifreeze (for the car, like ) polar? Epsom salts? Car oil? Animal fat? Artificial sweetener (such as Nutrasweet or Splenda)? Sand?

Take Home Lab #7

Take Home Lab #7: Growing Crystals

Question: How are crystals of different chemicals similar and different?

Safety: Use only hot tap water; do not heat water in a microwave or on the stove. Do not eat any of the crystals or other materials during this activity, as mold quickly grows on some of the crystals. Mark the cups clearly and keep them out of the reach of children. Clean up spills immediately. Cover the sugar crystals to avoid ants seeking it out.

Materials: Cups, water, sugar, salt Epsom salt, thread, pencil, paperclip

Procedure: In this lab, you will grow three different types of crystals: Sugar, salt, and Epsom salts. Crystals are grown by either dissolving more material than the solvent can normally hold by heating it, or by allowing the solvent to evaporate over time. In this procedure, you will do a little of both. Your will put a lot of solute in a little solvent and heat it to dissolve; then you will let it sit for a few days to evaporate.

1. For each of the solutes, dissolve a large spoonful in about 30 mL of hot tap water. Stir until all of the solute is gone.

2. Once all of the solute has dissolved, transfer the solution to a disposable cup, leaving any undissolved solid behind. Hang a short thread in the solution. If the string will not sink, you can tie a paper clip to the end. Allow it to sit on a windowsill for several days while the water evaporates. Pull the string out and let the crystals dry overnight. Record observations of the crystals every day and include the number of crystals, size, shape and other characterisitcs.

3. Find a good example of each crystal and sketch its shape. Try to find a single crystal without other crystals growing out of it. If your crystals are small, you can look at them under a magnifying glass. Just place in a bag and bring to school.

Post-Lab Questions:

1. Every day make a quick sketch of your different crystals and label Day 1, Day 2 and so forth.

2. Make sure to sketch your crystals after you take them out of the solvent.

3. Which substance grew the largest crystals?

4. How would you describe the shape of each crystal?

5. If equal masses of each substance were used, then the one with the lowest molar mass would have contained the largest number of molecules of that substance and would have the highest concentration. The highest concentration should grow the fastest but will produce the smallest crystals. Use the formulas to determine if your crystals followed this patter, NaCl (salt), C₁₂H₂₂O₁₁ (sugar), and MgSO₄ (Epsom salt). Did the substance with the highest molar mass grow the largest crystals?

Homework for 3/23 (#9)

1) HW#9:  pg. 539 ex 15.8, pg. 540 #7, 556 #31-34, Read Chpt 16
2) Test on Thursday
3) All late HW due Thurs 3/26 & composition books due

After School Tutoring Review Chapter 13

If you received less than a C on the Chapter 13 test, there will be a review on Thursday, March 19th to review the concepts and receive extra credit. Tutoring will last approximately one hour. 

Changing Boiling Point of Water Lab

Make sure calculations for #1-6 are done when you arrive to class on Thursday!

Changing the Boiling Point of Water

Purpose

To determine how adding a solute to water will affect the boiling point of water.

Calculations:

1. Calculate the molar mass of NaCl.

2. Determine the amount of salt needed in grams to make a 0 M solution of salt that has a volume of 200 mL.

3. Determine the amount of salt needed in grams to make a 0.5 M solution of salt that has a volume of 200 mL.

4. Determine the amount of salt needed in grams to make a 1.0 M solution of salt that has a volume of 200 mL.

5. Determine the amount of salt needed in grams to make a 1.5 M solution of salt that has a volume of 200 mL.

6. Determine the amount of salt needed in grams to make a 2.0 M solution of salt that has a volume of 200 mL.

Kool Aid Lab

Kool-Aid Lab

Objective:                       

This activity reviews stoichiometry and solutions by making different concentrations of a Kool-Aid solution. There are many ways to calculate the concentration of a substance including: molarity (M), parts per million (ppm), percent composition (% comp), and grams per liter (g/L).

In chemistry, concentration is usually measured by the number of moles of substance dissolved in a liter of liquid. This is called molarity and is expressed as M (formula: molarity = moles/volume).

Pre-lab Questions:

1.   Calculate the molar mass of Kool-Aid. Assume the solute is pure table sugar, called sucrose.  Its chemical formula is C₁₂H₂₂O₁₁.

2.   What mass of Kool-Aid is needed to make a 1.0-M solution from 100 mL?

3.   What mass of Kool-Aid is needed to make a 0.5-M solution from 100 mL?

4.   What mass of Kool-Aid is needed to make a 0.2-M solution from 100 mL?

Purpose:

Apply your knowledge to calculate grams of Kool-Aid powder required to make three different solutions of Kool-Aid (C₁₂H₂₂O₁₁) with the following concentrations: 0.2 M, 0.5 M and 1.0 M. Determine the concentration (molarity) of properly prepared Kool-Aid through a taste test.

1. Hypothesis

Make an educated guess: Which of the 3 solutions will provide the best tasting drink?

2. Procedure

Part I:

1.  Create a data table to record the amount of Kool-Aid used (in grams), color, and taste ranking. Also create a data table to hold the data collected throughout this experiment.

	Grams used	Color	Taste ranking
control
0.2 M
0.5 M
1.0 M

2.  Select your taster(s). Taste the Kool-Aid and rank on a scale of 1–5 (1 = gross and 5 = amazing taste).

3.  Mix the Kool-Aid (C₁₂H₂₂O₁₁) exactly following the directions for one serving size.  

Part II:

	Observations	Saturation?
Control
0.2 M
0.5 M
1.0 M

1.  Record your observations: (ex. looked like? Taste? Which seems more concentrated, saturated, supersaturated, unsaturated?)

3. Analysis

(Reminder: 1 gram H₂0 = 1 mL; 1 L = 1,000 mL)

1.  A chemist makes two Kool-Aid solutions with varying concentrations.  The chemist makes solution A by dissolving 50.0 g of sugar in 400.0 mL of water.  She then makes solution B by dissolving 50.0 g of sugar in 200.0 mL of water.  What can be said about the solution’s concentrations? (use at least three of the following terms in your explanation: saturated, dilute, supersaturated, homogeneous, unsaturated, solvent, solute, solution)

2. If you were working for the Kool-Aid company, which concentration would you recommend to customers? Explain why, using evidence and reasoning to support your claim.

3. If 104 grams of Kool-Aid was dissolved in enough water to make 3.60 L of solution, what would be the Molarity?

4. Bryan loves Kool-Aid. He makes a super-concentrated solution of Kool-Aid by heating water to boiling and then dissolving Kool-Aid until no more would dissolve. After cooling, he notices that there is a bunch of Kool-Aid powder on the bottom of his solution.  What happened? Explain your answer.