Percent Alcohol in Wine

Week 1 LabS117 Fall 2011

Overview

• Safety in the chemistry lab• Experimental Chemistry• Pre-lab: Percent Alcohol in Wine• Chemical Communication

Safety

• Preparation is the key—know what you are doing!

• Proper attire– Goggles--$8 at Undergrad Office – NO CONTACTS– Close-toed shoes– Long pants/skirts, t-shirt at minimum

• No eating, drinking, gum, or smoking• No horseplay—think safety

Safety: This Week in Lab• Sign Safety Rules• With AI’s, discuss:– Location of safety equipment– Working with chemicals– Disposal of waste– Procedure for minor cuts, spills– Meeting place for major

incident• Safety worksheet– Replaces quiz for this week

“It’s only a flesh-wound!”

Experimental Chemistry

• Scientific method• Experiment and theory, or theory and

experiment?• Pre-lab process:– Ask a question– What data needed?– How to acquire?

Which of these students is getting kicked out of lab?

Percent Volume of Alcohol in Wine

• The question: What is the percent volume of ethanol in various samples of wine?– Quantitative analysis– Sub-questions: Red vs. white wine? Brand?

• What data are needed to answer our question?– Direct measurement– Indirect (calculation)

Separation: Distillation

• Based on physical properties

• Problem: Limitation of simple distillation

• Key to science: problem solving!

Using Reference DataPercent by weight of ethanol in mixture

Density of mixture(g/mL)

Percent by weight of ethanol in mixture

Density of mixture(g/mL)

0.50 0.997 24.0 0.963

1.00 0.996 28.0 0.957

2.00 0.995 32.0 0.950

3.00 0.993 36.0 0.943

4.00 0.991 40.0 0.935

5.00 0.989 44.0 0.927

6.00 0.988 48.0 0.918

7.00 0.986 52.0 0.910

8.00 0.985 56.0 0.900

9.00 0.983 60.0 0.891

10.0 0.982 64.0 0.882

12.0 0.979 680 0.872

14.0 0.977 72.0 0.863

16.0 0.974 76.0 0.853

18.0 0.971 80.0 0.844

20.0 0.969 100.0 0.789

Table 1: Weight percent and density of ethanol/water mixtures

Measurement and Uncertainty

• Limitations of measurements• Uncertainty in values

• What do we need to do to acquire these data?

Calculations and Data Workup

• Develop a conceptual flow prior to algorithm• Direct calculation vs. comparison to data• Choice of measuring tools: beaker vs

graduated cylinder vs volumetric flask• Tools for data analysis: Excel

Chemical Communication

• Purposes of Formal and Informal Writing• Lab notebook– Title– Purpose/Objective/Question(s)– Experimental/Methods/Procedure– Results/Observations/Changes in Procedure– Comments– Conclusion

• Formal Report