Dry Ice Lab

Dry Ice Lab

Background: Dry ice is made of solid carbon dioxide (CO₂).  The same compound that you breathing out at this very moment.  It is far colder than water ice which freezes at 0°C, dry ice freezes at -78.5°C (-110°F).  Dry ice is used to ship food through the mail or to keep items cold where there is not a refrigerator.

Preparation Questions:

1. Taste the apple juice.  How does it taste, be as descriptive as possible.

Observe dry ice:

3. Make observations about what happens to the dry ice as it is left at your table.

4. Make at least three observations about how it is different from water ice.

5. When a metal object is placed on the dry ice what occurs? Compare this to what happens when you stretch out the opening of a latex balloon to make the opening very small. 

6. What happens when dry ice is placed in cup with plastic wrap on top?  Why does this happen?

7. Pour the dry ice vapor over the lit candle.  What happens to the candle?  Explain why this happens.

Dry ice in water:

8. What happens when dry ice is placed in warm water? Is this a physical or chemical change, explain why.

9. Is the water boiling?  What are the bubbles going up in the cup?

10. When “steam” comes out of the beaker, it goes down instead of up like steam from a pot of boiling water.  Why do you think this happens? (Hint: think about what you know about density!)

11. Observe the dry ice after it has been in the water for a long period of time.  What happens to the dry ice?

Dry ice in soapy water:

12. What happens when dry ice is placed in the soapy water.

13. Feel the bubbles from the dry ice in soapy water.  How do they feel different from regular bubbles?

14.  What observations can you make when you pop the bubbles?

Apple juice & dry ice:

15. Drink the apple juice after the dry ice has disappeared.  Does it taste any different?

16. Does it remind you of anything else that you drink? Compare it to other beverages that you have drank. Do you think this is a physical or chemical change? Explain why.

Questions:

19. Draw the cycle of the changes of state of matter.  What is the name of the change that is happening to the dry ice? Is it losing or gaining energy? Is this a physical or chemical change, explain.

20. Explain why the dry ice changed rapidly when it was placed in hot water. Think about the energy change that occurred.   

21. How is dry ice different from water ice?  Explain at least three differences.

22. Did the dry ice float or sink in the water?  How does this compare to water ice? Which one is less dense/more dense?

Take Home Lab #3

Take Home Lab #3:  Probability of Finding an Electron

Question: What does it mean to say that an electron has a probability of being found in a certain location around the nucleus?

Safety: No safety concerns.

Materials: Pen or pencil, copy of target

Procedure: It is known that electrons do not actually fly around in fixed orbits like planets. When you see textbook drawings of electrons in orbits, the orbits only represent where it is the most probable that the electron may be found at any moment. Sometimes this is called the electron cloud. The electrons also do not form a cloud; that is just a model representing the likelihood that an electron will be found at a certain location. You will simulate this probability analysis by dropping a pen at a target and counting how many times the pen marks in each area.

1. Take the target paper and put it on the floor. While aiming for the center of the target, hold the pen at arm’s length, drop it 50 times, tip first, so that it will make a mark on the paper.

2. Count how many times the pen struck each of the areas on the target. (Enter this on the hits part of your data chart) If it is on the line, try to determine which side it is closer to hitting. Then count the total hits inside of that circle (for example, for circle 4, that would be all the hits in circle 1, 2, 3, and 4—Enter this in total hits on your data table).

3. Fill in the chart and graph your results with a smooth curve. Then calculate the probability using the equation (total hits/total drops) x 100. Make a bar graph showing the probability.

Data

Circle 1	Hits =	Total hits:	Area= 4.9 cm2	Probability = ___%
Circle 2	Hits =	Total hits:	Area= 14.7 cm2	Probability = ___%
Circle 3	Hits =	Total hits:	Area= 24.5 cm2	Probability = ___%
Circle 4	Hits =	Total hits:	Area= 34.4 cm2	Probability = ___%
Circle 5	Hits =	Total hits:	Area= 44.2 cm2	Probability = ___%
Circle 6	Hits =	Total hits:	Area= 53.0 cm2	Probability = ___%

      Probability

 

                                                Area

Wrap-Up

1. In which circle did the most hits occur?

2. Scientists consider the size of the 1s orbital to be the circle in which there is a 90% chance of finding the 1s electron. Which is the smallest circle that contains 90% of your dots (45 dots)?

3. If you dropped your pen one more time, could you assume that it will fall in the ring noted in #1?

HW #9

1) HW #9 pg. 406 #1-3, pg. 435 #1-5
2) Take Home Lab #3 due Monday
3) Make up lab for one of the Take Home Lab #1 or #2 due Monday

HW #8 for 10/29

1) HW #8 pg. 235-6 #35-36, 42
2) Take Home Lab #3 & make up lab due Mon 11/2
3) Make up test after school by Friday

HW #7 for 10/27

1) HW # 7: pg. 235 #33-34
2) Test make up due by Friday 10/30, has to be done after school
3) Make up take home lab due 11/2

Color Change Challenge Lab

Color Change Challenge

Objective: Given four different colorless solutions, can you discover the correct sequence of combining the solutions that will result in specific color changes? What is you were given a limited amount of each solution—could you determine the minimum number of steps required to accomplish the goal?

Background: Scientists use many different strategies to solve problems. One such strategy is known as trial and error. The purpose of trial and error is to test multiple possibilities for solving a problem, but not necessarily to find out why the solution works. The term trial and error may lead some to believe that when a test (the trial) leads to an incorrect solution (the error), then the experiment has failed. On the contrary, the experimenter has gained valuable knowledge—learning what does not work!  Trial and error is often used to discover new medicines and is a great strategy for producing new inventions. Thomas Edison (1847-1931), the famous inventor, once said, “I have not failed. I’ve just found 10,000 ways that won’t work.”

            The activity uses the problem-solving strategy of trial and error to identify a series of chemical changes that will result in specific color changes. A chemical change is defined as a change in the composition and properties of a substance. The transformation of original substances (reactants) into new substances (products) as a result of a chemical change is called a chemical reaction.  Both in the natural world and in the laboratory we recognize that a chemical reaction has occurred by observing the appearance of products with physical and chemical properties different from the reactants from which they were made.

Goal: The purpose of this experiment is to mix four solutions labeled A, B, C and D in the correct sequence to produce a series of color changes—from colorless to orange, then to bluish-black, and finally back to colorless again. The testing procedure should be planned in advance to accomplish this goal in the minimum number of steps possible. Keep in mind that you have a limited amount of solution to test.

Pre-Lab Questions:

1. Starting with the four available solutions (A, B, C, D), how many different combinations of any solutions are possible? (Note: adding solution A to solution B will produce the same result as adding solution B to solution A.)

2. What are signs of a chemical reaction? What will you be looking for in your observations?

3. Working with a partner, write a general outline describing an “action plan” of steps to test the possible combinations of solutions. This action plan can be written as specific numbered steps or as a graphic organizer as a flow chart or other diagram. Allow for more than one possible correct sequence.

Procedure:

1. Obtain a testing tray and place it in the center of your work area.

2. Obtain one of the labeled pipets from the pipet holder. Be careful to not squeeze the bulb until you are ready to dispense the solution.

3. Place 5 drops of the chosen solution into one well of the testing tray. Use the diagram of the spot plate in your lab book to record which solution was placed in the first well.

4. Return the pipet to the pipet holder.

5. Following your action plan then select the second pipet and place 5 drops of the second solution into the same well as the first solution. Stir with a clean toothpick. Record the combination on the diagram. For example A + B.

6. Observe any changes in the color and appearance of the mixture and record your observations in the well on the diagram.

7. Continue with the same general procedure for other combinations of two, three, and four solutions until the correct sequence of colored products is obtained—from two colorless reactants to an orange product, then adding another reactant to any orange solutions to produce a bluish black solution, and finally adding the fourth solution to end with a colorless product.

8. Clean your testing tray as needed.

Post-Lab Questions:

1. Write out the order in which the solutions were combined to produce the desired series of color changes—colorless to orange to dark blue and back to colorless. Could there be more than one correct sequence?

2. The number of wells used is an indication of the number of steps that were needed to discover the correct sequence? Do you think the solution could have been discovered in fewer steps? Why or why not?

3. Adding solution A to solution B would produce the same result as adding solution B to solution A. Would reversing the entire order in which the four solutions were mixed (see Question #1) produce the desired series of color changes? Explain.

4. Briefly describe an everyday situation in which trial and error might be used to explain a problem.

ID of Chemical Reactions Lab

Identification of Chemical Reactions

Objective: To identify the mystery solution by observing all the possible combinations and comparing those observations to the mystery solution.

1. Give a physical description of each of the seven solutions that you will use today.

                      Name:

Solution #1: ____________________________

Solution #2: ____________________________

Solution #3: ____________________________

Solution #4: ____________________________

Solution #5: ____________________________

Solution #6: ____________________________

Solution #7: ____________________________

2. Mix every possible combination using 3-4 drops of each solution in the cavities of your testing tray.  Stir each mixture with a clean toothpick (use both sides of toothpick).  Record your observations and tell whether if it was a chemical or physical change that occurred.

Sol. #1 with #2:

Sol. #1 with #3:

Sol. #1 with #4:

Sol. #1 with #5:

Sol. #1 with #6:

Sol. #1 with #7:

Sol. #2 with #3:

Sol. #2 with #4:

Sol. #2 with #5:

Sol. #2 with #6:

Sol. #2 with #7:

Sol. #3 with #4:

Sol. #3 with #5:

Sol. #3 with #6:

Sol. #3 with #7:

Sol. #4 with #5:

Sol. #4 with #6:

Sol. #4 with #7:

Sol. #5 with #6:

Sol. #5 with #7:

Sol. #6 with #7:

Unknown Sol. with #1:

Unknown Sol. with #2:

Unknown Sol. with #3:

Unknown Sol. with #4:

Unknown Sol. with #5:

Unknown Sol. with #6:

Unknown Sol. with #7:

3. What is the identity of the unknown solution (give the name of the solution)?:

4. What signs of a chemical reaction did you observe?

5. Identify the ions that make up these ionic compounds and write the cation or anion (make sure to include its charge) and give the formula.  (example: silver chloride—Ag⁺ and Cl^- and formula AgCl)

          a. calcium chloride

          b. sodium oxide

          c. beryllium oxide