CHEM1001 Lecture Notes - Lecture 17: Sugar Alcohol, Vegetable Oil, Glycerol

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1 Aug 2016

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When an object is placed in water, the object"s relative density determines whether it floats or sinks. If the object has a lower density than water, it will float to the top of the water. Cork has a density of 240 kg/m3, so it will float. Air has a density of approximately 1. 2 kg/m3, so it rises immediately to the top of a water column. The metals sodium and potassium will both float on water, while lead will sink. The sugar alcohol glycerol will sink into the water and form a separate layer until it is thoroughly mixed. Vegetable oil will float on water, and no matter how vigorously mixed, will always return as a layer on the water surface. Even if the pressure is consistent, water"s density will change based on the temperature. Recall that the three basic forms of matter are solid, liquid and gas.

Related Questions

Plastics Identification Data Table
Letter Label	Sampleâs Color	Sampleâs Shape	Floats in Water? (Yes/No)	Sinkersâ Boiling Water Results (Note color/shape changes.)	Sinkersâ Acetone Test Results (Note texture changes.)	Floatersâ Alcohol Test Results (Note number of squirts.)	Plastic Type
A
B
C
D
E
F
G

Questions

Why does PP float before HDPE and LDPE in the alcoholâwater solution?

Did any of the four plastics melt in boiling water? (Hint: How does melting differ from softening in plastics?)

When PS reacts with acetone, is this a physical or chemical change? Explain.

What is the approximate density of the alcoholâwater solution that was diluted with water to help identify LDPE from HDPE?

Looking at plastic containers like milk jugs, deli boxes, detergent bottles, soda bottles, and pill vials makes a person wonder whether they are really all that different from one another. The numbers and letters in the recycle codes seem to indicate that the plastics arenât the same, because these codes all refer to different kinds of plastics. For example, HDPE (high-density polyethylene) has the plastics recycling code number 2, while number 3 is used for PVC or V (polyvinyl chloride). An example of the polyethylene terephthalate (PETE) recycle code is shown at right. In this Activity, you will follow a flowchart to determine the identity of all seven recyclable plastics, without their labels; the first separation involves comparing the densities of plastic pieces to water.

A recycling plant may use manual separation of containers by having people visually recognize and remove containers as they travel along a conveyor belt. All of one kind of plastic will be collected at one location in the plant. Automated sorting may use whole containers or cut-up containers, called flake. Flake sorting involves putting the flakes into large containers of water to separate the âfloatersâ from the âsinkersâ. Whole container sorting uses electromagnetic radiation such as visible, near infrared, and X-ray systems. Optical sorting uses visible light to sort containers by color. Containers exposed to near infrared light absorb specific wavelengths and transmit others based on crystallinity of the plastics. Sensors detect the change in wavelength for each container and initiate the sorting by using jets of air to blast a container to a specific location. X-ray systems detect chlorine atoms in PVC. Recycle plants may sort plastics by using a combination of the systems described above or other technologies that are currently being developed.

Try This

You will need: seven kinds of plastic containers with different recycle codes, scissors, two cups or beakers, two stirring rods or wooden craft sticks, room temperature water, 70% isopropyl alcohol, graduated cylinder, acetone, 2 plastic pipets, hot plate with a 400 mL beaker of boiling water (student groups may share the boiling water), tongs, and forceps.

Cut a small, flat piece (1.5 cm Â´ 1.5 cm) from each container (seven total) and start a data table to record the color and shape of each piece as well as the permanent marker letter label (AâG) your instructor previously marked on each container. If two containers are the same color, cut different shapes (triangle, rectangle, circle, etc.) to help with piece identification. Now you are ready to follow the flowchart. Record your observations in the data table as you go along.

Tap Water Test: Place all seven pieces of plastic in a beaker or cup of room temperature tap water. Stir vigorously with a stirring rod or wooden craft stick to dislodge any bubbles from the plastic pieces. Bubbles tend to adhere to plastics. How would this change the apparent density? Observe and record which pieces sink and which float.

70% Alcohol Test: Remove the pieces that float from the water. Add them to a beaker or cup containing about 20 mL of 70% isopropyl alcohol. Stir. Do the pieces sink or float in the 70% alcohol? How does the density of alcohol compare to water?

Using a plastic pipet, add a squirt of tap water to the beaker containing alcohol. Stir. Do any of the pieces begin to float? When adding water to 70% alcohol, how does the density of the solution change? Keep adding squirts of water and stir until one piece floats. According to the flowchart, what is the identity of this plastic? Remove the piece and record your results.

Add more squirts of water until a second piece floats. Remove the piece and record the identity of the second plastic. You can now identify the third piece since it is still sinking.

Boiling Water Test: Place the four pieces that sank in tap water in the beaker of boiling water for a minimum of 30 s. Using tongs, remove them one at a time and test their flexibility, noting their size and color. Record your results. Which plastics can you now identify using the flowchart?

Acetone Test: Place the final two plastic samples in a small amount of acetone for one minute. Record your results.

Check with your instructor to see whether you correctly identified the seven plastics. You are now ready for an unknown. If your unknown floats in the tap water test, you will need to use the known pieces for PP, HDPE, and LDPE along with your unknown to help you with the identification in the 70% alcohol test.

More Things To Try

You might want to explore plastics coded as 7, âotherâ, or âmixedâ with this approach (see the figure at right). The results may be inconclusive because two or more polymers may be used to make these containers, or it might be 95% of one plastic and 5% another so that it will test as one component. Some containers have many additives to give the container a softer texture; some have several coloring agents. These additives will alter the density of the plastic. Another experiment to try is to test whether black microwavable PET dinner trays react like the transparent PET bottles.

Need help answering the pre - lab questions

Chemistry 1010 Laboratory Fall 2016 Lab: Percent Sugar Content of Beverages ave you ever been to the ocean? Does it seem that you can float or swim much easier in the ocean than in a swimming pool? Seawater is more dense than freshwater due to the presence of dissolved salt in the cean As a result, our buoyancy-ability to float-is greater in salt water than in plain water. What factors of a particular substance is dissolved in it? Background The density of a pure substance is a characteristic physical property that can be used to identify the substance does not depend on the amount of the substance. The density of any material is determined by measuring its mass and volume and then dividing the mass by the volume. The mass of a substance can be measured directly using a balance. The volume of a liquid can be measured directly using special laboratory glassware, such as a graduated cylinder, buret, or pipet. In this experiment, liquild volumes will be measured using a graduated cylinder Density is defined as the ratio of mass per unit volume. It is an "intensive" property, that is, it The density of a solution depends on its concentration, that is, how much solid is dissolved in the liquid. The higher the concentration of solid, the greater the density of the solution. A convenient way to express concentration is in units of weight percent, which corresponds to the number of grams of sollid that are present in 100 g of solution. A 20% salt solution is prepared by dissolving 20 g of sodium chloride (table salt) in 80 g of water to give a final mass of 100 g of solution. When the density of a solution is plotted on a graph against the concentration of the solution, a regular pattern becomes evident, specifically that density is directly proportional to the concentration of solid in the solution. A 20% salt solution, for example, has a higher density and higher concentration of solid than a 10% salt solution. If the densities of several solutions of known concentration are determined experimentally and plotted on a graph, a calibration curve can be drawn to show a straight-line relationship between the density of a solution and the concentration of solid (note: the calibration curve in this lab reveals a linear (straight-line) relationship, but not all calibration curves are linear). The calibration curve can then be used to find the concentration of solid in an unknown solution simply based on experimentally measuring the density of the solution. Experiment Overview The purpose of this experiment is to determine the percent sugar content in beverages. The density of five reference" solutions will be determined in Part A. The reference solutions contain known amounts sugar " of sugar (0-20%). Their densities will be plotted on a graph to obtain a calibration curve of density versus nt sugar concentration. In Part 8, the densities of two beverages will also be determined, and the The results will be compared against the information provided on the nutrition labels for these beverages 1. if the following mass and volume data are used to calculate the density of solution, how many cal libration curve, created from the data in Part A, will be used to find the percentage of sugar they contain. Pre-Lab Questions significant figures are allowed in the calculated density? Mass of solution 12.53 g: volume of solution = 8.27 mL Calculate the density of the solution described in Question #1 (Hint: This is a 2-step problem. Then calculate the percent sugar in the beverage.) According to its nutrition label, orange soda 2. 3. First, use the density to convert the 355-mL serving size to grams. Lab: Percent Sugar Content of Beverages

1.A block of metal has dimensions 5.00 cm x 2.50 cm x 3.00 cm. Calculate the volume of the block, showing the answer to the correct number of significant figures and unit.

2.If the block of metal from question 2 has a mass of 405.3 g, what is the density of the metal? Calculate the density, showing the answer to the correct number of significant figures and correct unit.

3.Convert the numerical value of the density in question 2 from units of grams per cubic centimeter (g / cm3) to milligrams per milliliter (mg / mL). Note:

-there are 1000 milligrams in a gram.

-the volume unit cubic centimeter cm3 equals the milliliter mL.

Keep the new density to the same significant figures as you reported in question 2

4.A finely-powdered white solid is known to be homogeneous mixture rather than a pure substance. A sample of this solid completely dissolves in water. Give TWO possible substances that could make up this solid mixture, and briefly explain your choices.

5.If your percent SALT in Lab 2 is relatively low, it can be assumed that some salt did not go into the filtrate (the liquid that passes through the filter paper), but rather may have been trapped with the sand. Explain briefly how you could recover any of this "missing" salt?

6.A brand of aspirin claims to contain 325 mg (1 g = 1000 mg) of aspirin per tablet. In addition to pure aspirin, a tablet also contains a non-active filler. We assume that the tablet contains only these two components: aspirin and filler. If a single tablet weighs 1.17 g, calculate the percent filler. Hint: calculate percent aspirin FIRST using the formula

% aspirin = [ (mass aspirin Ã· mass tablet) x 100], the find % filler. When using this formula, make sure the masses of aspirin and tablet have the same units.

7.Water has a density of 1.00 g/mL, and chloroform has a density of 1.49 g/mL. These two liquids do not mix with each other, but rather, form two layers when combined.

8.Equal volumes of water and chloroform are placed in a beaker. A piece of nylon is dropped in the beaker, and is seen to float the the interface (the boundary) of the two liquid layers.

Give a possible value for the density of nylon, including the correct units. Explain your answer briefly.

9.A procedure similar to that used in Lab 3 was performed to find the density of cyclohexane, which has an actual density of 0.779 g/mL, Due to poor lab technique, an experimental density of only 0.663 g/mL is found. Calculate the percent error for the density. Give your answer to the correct number of significant figures.

10.Two white powders are given to you. One is pure sodium bicarbonate, and the other is baking powder (a mixture of sodium bicarbonate and a weak acid like citric acid). Which single test (NOT counting the visual examination with a hand lens) used in Lab 3 allows you to distinguish sodium bicarbonate from baking powder? Explain your answers completely.

11.Gold has a specific heat of 0.129 J/g^oC. If a piece of gold (initially at 10.0^oC) is dropped into hot water, the final temperature of both the gold and the water is measured as 70.9^oC. If it is known that 4560 J of heat transferred from the hot water to the gold, what is the mass of the piece of gold in grams? Give your answer to the correct number of significant figures.

12.It is stated in the Introduction to Lab 4 that q_water = -q_metal. This equation means that if a hot piece of metal is placed in water, the amount of heat given off by the metal is exactly equal to the amount of heat absorbed by the water. However, this equation is not always accurate, because not all of the heat from the metal necessarily goes to the water. Where else can some of the heat go if it is not absorbed by the water?

13.A certain brand of breakfast cereal claims to have 100 Calories per 28 gram serving. 150.0 grams of cereal are burned using a procedure similar to that used in Lab 4. How many calories of heat are released? Note 1 food Calorie (capital C) = 1000 heat calories (lower case c)

14.The oxalate anion C2O42- is found in many dark green vegetables, including spinach, swiss chard, and collard greens. When cations react with oxalate, the resulting ionic compounds are insoluble in water except Group I A oxalates (e.g. compounds of lithium, sodium, potassium, etc. and oxalate) and ammonium oxalate (NH4)2C2O4. These exceptions are soluble in water.

15.Spinach leaves are cut into small pieces, mashed with small amounts of boiling water, and filtered through filter paper to remove the insoluble spinach material. The resulting aqueous extract contains the oxalate anion.if a small amount of the spinach extract is mixed with a small amount of a calcium acetate solution, Ca(C2H3O2)2(aq), what do you expect will be observed?

16.If a small amount of the spinach extract from question 16 is mixed with a small amount of a potassium acetate solution, KC₂H₃O₂(aq), what do you expect will be observed?

17.If a hot water extract of another vegetable is mixed with calcium acetate solution and a white precipitate is observed, does this automatically indicate the presence of the oxalate anion in this vegetable? Explain your answer.

CHEM1001 Lecture Notes - Lecture 17: Sugar Alcohol, Vegetable Oil, Glycerol

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