Science Reasoning
Section A
Canned vegetables do not taste as good as fresh ones, and they also have fewer nutrients.
Scientists have studied what happens to several nutrients in vegetables during the entire process from
when they are picked in the field until they reach the consumer. The following two tables summarize
research on two of the main sources of degradation - effects due to the canning process and effects
due to storage over time and at various temperatures
Table 1
Table 2
1. Which factor appears to have the most impact on the thiamin content of canned spinach?
Storage time
Storage temperature
The canning process
Time, temperature and canning all have equal effects.
2. Cans of vegetables must have labels describing the nutrient content. Company A feels that if those
estimates are off by more than 12% within one year, then they are no longer in compliance with the law.
If company A cannot afford to store their cans at less than 65 degrees Fahrenheit, which vegetable(s)
should they NOT try to can and store for one year? (Assume that the amount of nutrient listed on the
can is the amount present immediately after the canning process.)
Green Beans
Lima Beans and Green Beans
Spinach and Lima Beans
Green Beans, Spinach and Lima Beans
3. Suppose a can of green beans is stored at 70 degrees Fahrenheit for 2 years. What is a reasonable
guess for the percent of riboflavin that remains, as compared with the first day the can was put on the
shelf?
72%
67%
50%
35%
4. If green beans are stored at 50 degrees Fahrenheit for 4 years, what percentage of the ascorbic
acid will be retained?
88%
80%
Less than 74%
There is insufficient information to answer
5. If lima beans are picked, canned and then stored for 2 years at 65 degrees Fahrenheit, about what
fraction of the original riboflavin content is retained?
1/4
1/2
2/3
3/4
Section B
When food is cooked, only some of the nutrients are preserved. Food scientists performed two
experiments to study the retention of vitamin C after potatoes were cooked. The scientists measured
the retention of ascorbic acid (AA) and dehydroascorbic acid (DAA). The sum of the amounts of AA and
DAA equals the total amount of Vitamin C.
Experiment 1
In this experiment, potatoes were peeled and then fried. The following table shows the stability of
ascorbic acid and dehydroascorbic acid after frying. The concentrations of AA and DAA are given in
milligrams per 100 grams of dry potato.
Experiment 2
In this experiment, potatoes were peeled and then boiled in water with varying concentrations of NaCl.
The following table shows the stability of ascorbic acid (AA) and dehydroascorbic acid (DAA) after
boiling.
6. What concentration of ascorbic acid would you expect to see if potatoes were fried for 45 minutes at
140oC?
0 mg/100 grams
7.3 mg/100 grams
20.6 mg/100 grams
There is insufficient evidence to answer
7. If some potatoes were boiled in a 10% NaCl solution, and there were 300 grams of potato left, how
many milligrams of vitamin C would there be?
14.7
17.4
26.7
44.1
8. If a potato is boiled in water with 5% NaCl, about what percentage of the original vitamin C will be
lost?
31%
36%
52%
64%
9. Suppose some potatoes were peeled and cooked in water with 8% NaCl. What is a reasonable
guess for the concentration of DAA after the potatoes are cooked?
9.7 mg/100 grams of potato
8.1 mg/100 grams of potato
6.4 mg/100 grams of potato
5.4 mg/100 grams of potato
10. Which of the following statements accurately reflects the experimental results?
There is more DAA in fried potatoes than in raw, uncooked potatoes.
There is more AA in fried potatoes than in raw, uncooked potatoes.
There is more total vitamin C content in fried than in raw, uncooked potatoes.
There is more AA in fried potatoes compared with uncooked potatoes, but only if they are
fried at 140oC or lower.
11. All of the following explanations could account for the different pattern of DAA retention when
comparing frying and boiling except:
When immersed in water, the AA is less likely to oxidize to become DAA.
When immersed in water, DAA is hydrolyzed to become 2,3-diketogluconic acid.
Frying increases the likelihood for DAA to break down into other compounds.
Frying dries out the potatoes and reduces the tendency for DAA to hydrolyze.
Section C
When heat is added to a gas, the temperature increases and the gas expands. If the gas is in a rigid
container, then the volume remains constant and the pressure increases. If the gas in a container that
can expand (for example a cylinder with a vertical piston), then the pressure remains constant but the
volume expands.
The amount of energy required to increase the temperature of one mole of gas is called the specific
heat; there is a specific heat for constant pressure (Cp) and a specific heat for constant volume ((Cv).
In equation form, this is written:
Delta Q is the energy required to raise the temperature of the gas by a certain amount (delta T). The
specific heats for a few gases, including monatomic gases such as helium and argon, and diatomic
gases such as nitrogen and oxygen, are given in the table below.
12. Let X be the energy needed to raise the temperature of 5 moles of nitrogen held at constant
pressure by one degree. Let Y be the energy needed to raise 5 moles of carbon monoxide by one
degree with the pressure held constant. What is the ratio X: Y?
5:7
1:1
7:5
7:9