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Science · Drill 36

Science practice 36

10 questions ~9 min recommended
⏱ 00:00
Score
—

Cooling of Lauric Acid

Temperature (°C) vs Time (min) graph showing cooling curve from approximately 55°C at 0 minutes to 20°C at 30 minutes123456

Substance Melting Point (°C) Boiling Point (°C)
Water 0 100
Isopropyl alcohol -90 82
Paraffin wax 59 343

78910

A sample of solid lauric acid was placed in a test tube and heated in a Bunsen burner in a chemistry classroom. The lauric acid melted. A thermometer was carefully placed in the test tube to measure the temperature of the sample. The burner was then turned off, and the sample was allowed to cool; the temperature was recorded in Figure 10.4. The warm liquid sample crystallized into a solid while the temperature was being recorded.

Figure 10.4

TABLE 10.5

The melting point of a substance is the temperature at which that substance changes from the solid to the liquid phase. The boiling point of a substance is the temperature at which that substance changes from the liquid to the gaseous phase. Table 10.5 shows the boiling and melting points of other common substances.

1. Based on Figure 10.4, the temperature of the lauric acid sample decreased most rapidly during which time interval?

2. The thermometer was carefully placed in the test tube to measure the temperature of the lauric acid. If the thermometer was allowed to rest on the bottom of the test tube, what temperature may have been recorded at the start of the experiment (0 minutes)?

3. During the experiment, particles of lauric acid could either decrease in temperature or change from a liquid to a solid-they could not do both at the same time. In which time interval(s) did the particles' temperature decrease?

4. What is the melting point of lauric acid?

5. What phase(s) of matter is present in the sample of lauric acid at 25°C?

6. The sample of lauric acid was allowed to remain in the room, and the clock continued to run. If the trend found in Figure 10.4 continued, what would the stopwatch read when the sample reached room temperature of 25°C?

7. If twice the amount of lauric acid were heated in the test tube, at what temperature would one expect the lauric acid to crystallize into a solid?

8. What would most likely have occurred if this experiment had been conducted in an oven set at 50°C?

9. According to the data in Table 10.5, what phase(s) of matter is present in the sample of isopropyl alcohol at 25°C?

10. The same experiment was conducted with a sample of water in a test tube. It was heated to 55°C and then removed from the heat and allowed to cool in the classroom. Which of the following graphs would most likely represent the results?

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