Experiment 1: neutralization of acids and bases

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Pre-Lab Questions

1. What should you always wear to protect your eyes when you are in the chemistry laboratory?

Safety glasses or safety goggles should always be worn inside a chemistry lab to protect your eyes.

2. Should you add acid to water or water to acid?

Always add acid to water.

3. Where should you dispose of broken glass?

They should be placed in the proper container for the disposal of sharps. They should never be tossed into a regular trash can.

4. What should you do if you spill a chemical on your hand?

You should immediately wash your hands with copious amounts of water and antibacterial soap.

Exercise 1: What Is It?

A chemical laboratory contains special equipment to use while you are performing an experiment. Locate each of the items pictured on the following pages in your lab kit, and place a check mark in the appropriate place when you find it. After you have completed this, sketch a picture and name any additional items that are located in your lab kit, classroom, or home that are likely to be useful for you in completing these labs.

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Beaker

50 mL ____x_____

Stir Stick__x_______

250 mL ___x______ Graduated Cylinder

10 mL ____x_____

image9.png100 mL __x_______

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Test Tube ___x______ Pipette ___x______ Petri Dish ___x______

Include your Drawings Here:

Experiment 1: Neutralization of Acids and Bases

image12.jpgIn this experiment, you will learn how to properly neutralize and dispose of acidic and basic solutions.

Materials

5 mL 4.5% Acetic Acid (vinegar), C2H4O2 (1) 10 mL Graduated Cylinder 8 Litmus Test Strips (Neutral) Permanent Marker 2 Pipettes 1 g Sodium Bicarbonate (baking soda), NaHCO3

4 Weigh Boats *Water

*You Must Provide

Procedure

1. Use the permanent marker to label three of the weigh boats as A - C.

2. Measure and pour approximately 5 mL of water into weigh boat "A".

3. Add 0.5 g sodium bicarbonate to weigh boat "B".

4. Measure and pour approximately 5 mL of water into weigh boat "B". Gently pipette the solution up and down until the sodium bicarbonate is fully dissolved in the water.

5. Measure and pour 5 mL acetic acid solution to weigh boat "C".

6. Use the litmus test strips to determine if the substances in weigh boats A - C are acidic or basic. This is accomplished by briefly dipping an unused strip of the litmus paper in each of the weigh boats. Record your color results in Table 2.

7. Pipette 1 mL of the sodium bicarbonate solution from weigh boat "B" into weigh boat "C". Gently swirl weigh boat "C" to mix.

8. Develop and record a hypothesis regarding the pH of weigh boat “C”. Record this in the Post-Lab Questions section.

9. Test the pH of weigh boat "C" using new litmus paper. Record your result in Table 3.

10. Repeat Step 9 four more times until all the sodium bicarbonate has been added to weigh boat “C”.

Table 2: Initial Litmus Test Results

Weigh Boat

Chemical Contents

Litmus Results

Additional Observations

A

B

C

Table 3: Neutralization of an Acid

Amount of Base

Litmus Result

1 mL

2 mL

3 mL

4 mL

5 mL

Post-Lab Questions

1. State your hypothesis (developed in Step 8) here. Be sure to include what you think the pH will be, and why.

2. What is a neutralization reaction?

3. When might neutralization reactions be used in a laboratory setting?

4. At what point was the acetic acid in weigh boat “C” neutralized?

5. What do you think would have been the results if a stronger solution of sodium bicarbonate was used? Would it take more or less to neutralize the acid? What about a weaker concentration of sodium bicarbonate?

Pre-lab Questions

1. List the atomic numbers for each of the following elements.

Iron

_________

Oxygen

_________

Calcium

_________

Nitrogen

_________

Potassium

_________

Hydrogen

_________

2. What determines if a bond is polar?

3. Use the periodic table to determine if potassium chloride (KCl) formed through covalent or ionic bonds? Use evidence from the Introduction to support your answer.

4. Research two common, polar molecules and two common nonpolar molecules. Draw their molecular structure and explain how the structure makes each molecule polar or non-polar.

Experiment 1: Slime Time

image13.jpgInks can be polar or non-polar. Polar solvents pick up polar inks, while non-polar solvents pick up non-polar inks. In this experiment, you will use inks to identify slime and silly putty as polar or non-polar. You will also use paper chromatography to verify the inks are correctly identified as polar or non-polar.

Materials

(1) 250 mL Beaker 5 mL 4% Borax Solution, Na2B4O7·10H2O Dry Erase Marker (1) 10 mL Graduated Cylinder (1) 100 mL Graduated Cylinder Filter Paper (Disk) Filter Paper (Square) 0.5 g Guar Gum Highlighter Permanent Marker 1 Popsicle Stick

Silly Putty® Ruler Wooden Stir Stick Uni-ball® Roller Pen *Distilled or Tap Water *Newspaper *Notebook Paper *Scissors *You Must Provide

Procedure:

Part 1: Making Slime

1. Weigh out 0.5 g of guar gum into a 250 mL beaker.

2. Measure 50.0 mL of distilled water into a 100 mL graduated cylinder and pour it into the 250 mL beaker that contains the guar gum.

3. Rapidly stir the mixture with a wooden stir stick for three minutes, or until the guar gum is dissolved.

4. Measure 4.00 mL of a 4% Borax solution into a 10 mL graduated cylinder and add it to the guar gum and water.

5. Stir the solution until it becomes slime. This will take a few minutes. If the slime remains too runny, add an additional 1.0 mL of the 4.0% Borax solution and continue to stir until the slime is the slightly runny or gooey.

6. Once you are satisfied with the slime, pour it into your hands. Be sure not to drop any of it on to the floor.

7. Manipulate the slime in your hands. Write down observations made about how slime pours, stretches, breaks, etc. in Part 1 of the Data section. CAUTION: Slime is slippery and if dropped it can make the work area slick.

8. Place the slime back into the beaker and WASH YOUR HANDS.

Part 2: Slime and Putty Ink Tests

1. On a piece of notebook paper make one 20 - 25 mm long mark of each of the inks you are testing (permanent marker, highlighter, Dry Erase, and Uni-ball® Roller Pen). Space the marks at least one inch apart. Use a pencil to label each mark with its description.

a. Water soluble inks include those in highlighters and certain pens.

b. Water insoluble inks include those in a permanent pen/markers, newsprint, and a dry-erase markers.

2. While the inks are drying, select a passage or a picture in the newspaper to test with the slime.

3. Develop a hypothesis stating whether or not you believe the slime produced in Part 1 will pick up newsprint ink. Record this hypothesis in the Post-Lab Questions section. Then, break off a small piece of slime that is 3 - 5 cm in diameter. Gently place this piece on top of the newspaper print, then carefully pick it up again.

4. Observe and record in Table 1 whether or not the ink was picked up onto the slime.

5. Break off another small piece of slime. Once the inks from Step 1 have dried gently place the slime on top of the first spot on the notebook paper, then carefully pick it up. Repeat this for each of the inks. Observe and record which inks were picked up (dissolved) by the slime in Table 1.

6. Repeat this ink testing two more times for accuracy.

7. Hypothesize which inks the silly putty will pick up in the Part 2 of the Data section. Then, perform the ink tests with the Silly Putty® according to the procedure outlined in Steps 5 - 6.

Part 3: Chromatography of Ink Samples

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Figure 7: Chromatography apparatus for Procedure Part 3.

1. Use a pencil or scissors to poke a small hole in the center of a piece of filter paper (see Figure 7).

2. Spot the filter paper evenly spaced approximately 2 cm from the small hole with the two insoluble inks and the two soluble inks that were used in Part 2, Step 1.

3. Obtain a ½ piece of filter paper. Fold the paper in half several times so that it makes a narrow wick.

4. Insert the wick into the hole of the spotted paper so that it is above the top of the filter paper by approximately 2 cm.

5. Fill a 250 mL beaker ¾ full with water.

6. Set the filter paper on top of the beaker so that the bottom of the wick is in the water. The paper should hang over the edge of the beaker with the spotted side up.

7. Allow water to travel until it is approximately 1 cm from the edge of the filter paper. Remove the filter paper from the beaker.

8. Observe which inks moved from where they were originally spotted. Record your observations in Part 3 of the Data section.

Table 1: Results of Ink Testing for Silly Putty®

Name of Ink

Picked up (dissolved)

Did not pick up

Trial 1

Trial 2

Trial 3

Trial 1

Trial 2

Trial 3

Newsprint

Highlighter

Uni-ball® Roller Pen

Permanent Marker

Dry Erase Marker

Data

Part 1

· Slime Observations:

Part 2

· Hypothesis for Silly Putty® (Procedure Part 2, Step 7):

Part 3

· Observations of inks following chromatography:

Post-Lab Questions

1. Record your hypothesis regarding the slime’s ability to pick up newsprint ink here.

2. Did the slime pick up water soluble or water insoluble inks? From these results, what can you conclude about the polarity of slime molecules?

3. Explain how you determined your hypothesis about whether or not silly putty would pick up water soluble inks. Was your hypothesis correct?

4. Were the inks you used properly classified as soluble and insoluble? Explain your answer.

Pre-Lab Questions

1. Nitrogen fixation is a natural process by which inert or unreactive forms of nitrogen are transformed into usable nitrogen. Why is this process important to life?

2. Given what you have learned about the hydrogen bonding shared between nucleic acids in DNA, which pair is more stable under increasing heat: adenine and thymine, or cytosine and guanine? Explain why.

3. Which of the following is not an organic molecule; methane (CH4), fructose (C6H12O6), rosane (C20H36), or ammonia (NH3)? How do you know?

Experiment 1: Testing for Proteins

The protein molecules in many foods provide the amino acid building blocks required by our own cells to produce new proteins. To determine whether a sample contains protein, a reagent called Biuret solution is used. Biuret solution contains copper ions. However, the chemical state of the copper ions in Biuret solution causes them to form a chemical complex with the peptide bonds between amino acids (when present), changing the color of the solution. Biuret solution is normally blue, but changes to pink when short peptides are present and to violet when long polypeptides are present.

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Figure 6: Biuret solution only is located on the far left side of the image (blue). Note the transition from blue to violet as proteins are added to the solution, causing the solution to transition from blue to violet.

image14.jpg Materials

(2) 250 mL Beakers 25 Drops Biuret Solution, H2NC(O)NHC(O)NH (1) Knox® Gelatin Packet 5 mL 1% Glucose Solution, C6H12O6 (1) 10 mL Graduated Cylinder (1) 100 mL Graduated Cylinder Permanent Marker 5 Pipettes

5 Test Tubes (Plastic) Test Tube Rack 5 mL Unknown Solution *Tap Water *Hot Water *Egg White *You Must Provide

Procedure

1. Label five test tubes 1, 2, 3, 4 and 5.

2. Prepare your testing samples as follows:

a. Mix one egg white with 25 mL water in a 250 mL beaker to create an albumin solution. Pipette 5 mL of this solution into Test Tube 1.

b. Mix the packet of Knox® gelatin with 50 mL hot water in a second 250 mL beaker. Stir until dissolved. Pipette 5 mL of this solution into Test Tube 2.

3. Pipette 5 mL of the 1% glucose solution into Test Tube 3.

4. Use the 10 mL graduated cylinder to measure and pour 5 mL of water into Test Tube 4.

5. Pipette 5 mL of the “Unknown Solution” into Test Tube 5.

6. Record the initial color of each sample in Table 1.

7. Develop a hypothesis regarding what you predict will happen when Biuret solution is added to Tubes 1 - 4. Record your hypothesis in the Post-Lab Question section. Then, pipette five drops of Biuret solution to each test tube (1 - 5). Swirl each tube to mix.

8. Record the final color in Table 1. Note: Protein is present in the sample if a light purple color is observed.

Table 1: Testing for Proteins Results

Sample

Initial Color

Final Color

Protein Present

1 - Albumin Solution

2 - Gelatin Solution

3 - Glucose

4 - Water

5 - Unknown

Post-Lab Questions

1. Record your hypothesis about what will happen when Biuret solution is mixed with the solutions from test tubes 1, 2, 3, and 4 here. Be sure to use scientific reasoning to support your hypothesis.

2. Write a statement to explain the molecular composition of the unknown solution based on the results obtained during testing with each reagent.

3. Diet and nutrition are closely linked to the study of biomolecules. How should you monitor your food intake to insure the cells in your body have the materials necessary to function?

4. The molecule pictured below produced a blue color when tested with Benedict’s reagent, a yellow color when tested with IKI, and a violet color when tested with Biuret reagent. Based on the structure shown below and these chemical results, what kind of biomolecule is this?

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Pre-Lab Questions

1. A concentration gradient affects the direction that solutes diffuse. Describe how molecules move with respect to the concentration.

2. How does the size of a solute affect the rate of diffusion? Consider the size and shape of a molecule in your response.

3. Does polarity affect diffusion? Explain your answer using scientific principles.

Experiment 1: Diffusion through a Liquid

image15.jpgIn this experiment, you will observe the effect that different molecular weights have on the ability of dye to travel through a viscous medium.

Materials

1 60 mL Corn Syrup Bottle, C12H22O11 Red and Blue Dye Solutions (Blue molecular weight = 793 g/mole; Red molecular weight = 496 g/mole) (1) 9 cm Petri Dish (top & bottom halves)

Ruler *Stopwatch *Tape *You Must Provide

Procedure

1. Use clear tape to secure one half (either the bottom or the top half is fine) of the petri dish over a ruler. Make sure that you can read the measurement markings on the ruler through the petri dish. The dish should be positioned with the open end of the dish facing upwards.

2. Carefully fill the half of the petri dish with corn syrup until the entire surface is covered.

3. Develop a hypothesis discussing which dye you believe will diffuse faster across the corn syrup and why. Record this in the Post-Lab Questions section. Then, place a single drop of blue dye in the middle of the corn syrup. Note the position where the dye fell by reading the location of the outside edge of the dye on ruler.

4. Record the location outside edge of the dye (the distance it has traveled) every ten seconds for a total of two minutes. Record your data in Tables 1 and 2.

5. Repeat Steps 1 - 4 using the red dye, the second half of the petri dish, and fresh corn syrup.

Table 1: Rate of Diffusion in Corn Syrup

Time (sec)

Blue Dye

Red Dye

Time (sec)

Blue Dye

Red Dye

10

70

20

80

30

90

40

100

50

110

60

120

Table 2: Speed of Diffusion of Different Molecular Weight Dyes

Structure

Molecular Weight

Total Distance Traveled (mm)

Speed of Diffusion (mm/hr)*

Blue Dye

Red Dye

*Multiply the total distance diffused by 30 to get the hourly diffusion rate

Post-Lab Questions

1. Record your hypothesis from Step 3 here. Be sure to validate your predictions with scientific reasoning.

2. Which dye diffused the fastest?

3. Does the rate of diffusion correspond with the molecular weight of the dye?

4. Does the rate of diffusion change over time? Why or why not?

5. Examine the graph below. Does it match the data you recorded in Table 2? Explain why, or why not. Submit your own plot if necessary.

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Experiment 2: Concentration Gradients and Membrane Permeability

In this experiment, you will dialyze a solution of glucose and starch to observe:

· The directional movement of glucose and starch.

· The effect of a selectively permeable membrane on the diffusion of these molecules.

image16.jpgAn indicator is a substance that changes color when in the presence of the substance it indicates. In this experiment, IKI will be used an indicator to test for the presence of starch and glucose.

Materials

(5) 100 mL Beakers 10 mL 1% Glucose Solution, C6H12O6 4 Glucose Test Strips (1) 100 mL Graduated Cylinder 4 mL 1% Iodine-Potassium Iodide, IKI 5 mL Liquid Starch, C6H10O5 3 Pipettes 4 Rubber Bands (Small; contain latex, handle with gloves on if allergic)

*Stopwatch *Water *Scissors *15.0 cm Dialysis Tubing *You Must Provide *Be sure to measure and cut only the length you need for this experiment. Reserve the remainder for later experiments.

Attention!

Do not allow the open end of the dialysis tubing to fall into the beaker. If it does, remove the tube and rinse thoroughly with water before refilling with a starch/glucose solution and replacing it in the beaker.

Note:

· Dialysis tubing can be rinsed and used again if you make a mistake.

· Dialysis tubing must be soaked in water before you will be able to open it up to create the dialysis "bag". Follow the directions for the experiment, beginning with soaking the tubing in a beaker of water. Then, place the dialysis tubing between your thumb and forefinger and rub the two digits together in a shearing manner. This should open up the "tube" so you can fill it with the different solutions.

Procedure

1. Measure and pour 50 mL of water into a 100 mL beaker. Cut a piece of dialysis tubing 15.0 cm long. Submerge the dialysis tubing in the water for at least 10 minutes.

2. Measure and pour 82 mL water into a second 100 mL beaker. This is the beaker you will put the filled dialysis bag into in Step 9.

3. While the dialysis bag is still soaking, make the glucose/sucrose mixture. Use a graduated pipette to add five mL of glucose solution to a third beaker and label it “Dialysis bag solution”. Use a different graduated pipette to add five mL of starch solution to the same beaker. Mix by pipetting the solution up and down the pipette six times.

4. Using the same pipette that you used to mix the dialysis bag solution, remove two mL of that solution and place it in a clean beaker. This sample will serve as your positive control for glucose and starch.

a. Dip one of the glucose test strips into the two mL of glucose/starch solution in the third beaker. After one minute has passed, record the final color of the glucose test strip in Table 3. This is your positive control for glucose.

b. Use a pipette to transfer approximately 0.5 mL of IKI to into the two mL of glucose/starch solution in the third beaker. After one minute has passed, record the final color of the glucose/starch solution in the beaker in Table 3. This is your positive control for starch.

5. Using a clean pipette, remove two mL of water from the 82 mL of water you placed in a beaker in Step 2 and place it in a clean beaker. This sample will serve as your negative control for glucose and starch.

a. Dip one of the glucose test strips into the two mL of water in the beaker. After one minute has passed, record the final color of the glucose test strip in Table 3. This is your negative control for glucose.

b. Use a pipette to transfer approximately 0.5 mL of IKI to into the two mL of water in the beaker. After one minute has passed, record the final color of the water in the beaker in Table 3. This is your negative control for starch.

Note: The color results of these controls determine the indicator reagent key. You must use these results to interpret the rest of your results.

6. After at least 10 minutes have passed, remove the dialysis tube and close one end by folding over 3.0 cm of one end (bottom). Fold it again and secure with a rubber band (use two rubber bands if necessary).

7. Make sure the closed end will not allow a solution to leak out. You can test this by drying off the outside of the dialysis bag with a cloth or paper towel, adding a small amount of water to the bag, and examining the rubber band seal for leakage. Be sure to remove the water from the inside of the bag before continuing.

8. Using the same pipette which was used to mix the solution in Step 3, transfer eight mL of the solution from the Dialysis Bag Solution beaker to the prepared dialysis bag.

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Figure 4: Step 9 reference.

9. Place the filled dialysis tube in beaker filled with 80 mL of water with the open end draped over the edge of the beaker as shown in Figure 4.

10. Allow the solution to sit for 60 minutes. Clean and dry all materials except the beaker with the dialysis bag.

11. After the solution has diffused for 60 minutes, remove the dialysis tube from the beaker and empty the contents into a clean, dry beaker. Label it dialysis bag solution.

12. Test the dialysis bag solution for the presence of glucose and starch. Test for the presence of glucose by dipping one glucose test strip into the dialysis bag directly. Again, wait one minute before reading the results of the test strips. Record your results for the presence of glucose and starch in Table 4. Test for the presence of starch by adding two mL IKI. Record the final color in Table 4 after one minute has passed.

13. Test the solution in the beaker for glucose and starch. Use a pipette to transfer eight mL of the solution in the beaker to a clean beaker. Test for the presence of glucose by dipping one glucose test strip into the beaker. Wait one minute before reading the results of the test strip and record the results in Table 4. Add two mL of IKI to the beaker water and record the final color of the beaker solution in Table 4.

Table 3: Indicator Reagent Data

Indicator

Starch Positive Control (Color)

Starch Negative Control (Color)

Glucose Positive Control (Color)

Glucose Negative Control (Color)

IKI Solution

n/a

n/a

Glucose Test Strip

n/a

n/a

Table 4: Diffusion of Starch and Glucose Over Time

Indicator

Dialysis Bag After 1 Hour

Beaker Water After 1 Hour

IKI Solution

Glucose Test Strip

Post-Lab Questions

1. Why is it necessary to have positive and negative controls in this experiment?

2. Draw a diagram of the experimental set-up. Use arrows to depict the movement of each substance in the dialysis bag and the beaker.

3. Which substance(s) crossed the dialysis membrane? Support your response with data-based evidence.

4. Which molecules remained inside of the dialysis bag?

5. Did all of the molecules diffuse out of the bag into the beaker? Why or why not?

© 2013 eScience Labs, LLC. All Rights Reserved

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