Lab Exam Flashcards
(50 cards)
Steps in the scientific process
- Observe and question
- Develop a hypothesis
- Conduct experiments
- Make conclusions
Hypothesis
an educated guess that may answer the question formed as a result of observation
Experiments
designed to test a given hypothesis; typically has one variable that gets changed to test the effects of change
Independent Variable
the thing that is changed in an experiment
Dependent Variable
the facts or data obtained from an experiment
Conclusions
made after the data is collected and analyzed
Theory
an idea with credible evidence to support it; occurs when a group of hypotheses that are related to one another undergo repeated experimentation without being rejected
HPLC stationary phase
molecules in a mixture that are more attracted to the solid, motionless absorbing agent
HPLC mobile phase
molecules in a mixture that are more attracted to the moving solvent
High Performance Liquid Chromatography (HPLC)
precision pumps used to measure, mix, and propel liquid through a tube packed full of a powdery solid adsorbant
HPLC adsorbant structure
carbon-18 (C18 chains attached to silicon atom)
HPLC procedure
each time: remove cartridge from the syringe, remove plunger, replace cartridge, insert solution, and replace syringe
1. precondition C18 adsorbant with 10 mL of 100% methanol
2. rinse C18 with 10 mL of DI water
3. add 1 mL of Kool-Aid and push out of syringe (label test tube KA)
4. pump 10 mL of DI water, label test tube “DI”
5. pump 10 mL of 5% methanol, label “5% MeOH’
6. pump 10 mL of 20% methanol, label “20% MeOH”
7. clean cartridge with 10 mL of 100% methanol
8. pour blue fraction onto red fraction
Which Kool-Aid dye was the least polar? Explain
blue dye, it stuck longer with the non-polar cartridge; the red dye moved slightly down with the polar water
Methanol collected the red fraction at ____% and the blue at ____%
20, 60
Isopropanol collected the red fraction at ____% and the blue at ____%
5, 20
Why did red and blue dye separate at different alcohol percentages?
Blue was less polar than red, so the red had a higher attraction to the polar water than blue, therefore being able to leave at a smaller percentage of alcohol
Why didn’t both alcohols separate the red and blue dyes at the same alcohol percentages?
The alcohols have different levels of polarity, isopropanol is less polar than methanol, therefore less of it is required to collect the dyes
What causes the layered effect when the blue dye is poured on the red dye?
Alcohol is less dense than water and there is a higher percentage of alcohol in the blue fraction.
Benedict’s test is for
monosaccharides and disaccharides (sugars)
A positive benedict’s test is the color…
yellow/green (small amount); orange/red/brown (large amount)
Iodine tests for…
starch
A negative iodine result will be the color…
yellow/orange
A positive iodine result will be the color…
brown (small amount); dark blue/black (large amount)
Sudan III tests for
lipids
