Melting Point and Boiling Point Lab Report

Categories: Chemistry

Report, Pages 4 (912 words)

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Introduction

For this experiment, the cooling curve will be utilized to calculate the cooling rate of substances as well as to produce cooling curves using various equipment. To draw conclusions and evaluate the accuracy of practical work in calorimetry in connection to cooling curve analysis, analyze the rate of cooling substances from the recorded data using cooling curves.

Aim

The aim of this experiment was to measure temperature and physical changes while analyzing cooling curves with paraffin wax and stearic acid and calibrating various thermometers.

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This assignment required demonstrating and describing how several techniques were used to examine cooling curves applying calorimetry. Calorimetry is the measurement of changes in chemical reactions, state, and phase concerning heat transferred or absorbed using a calorimeter in scientific research.

A calorimeter is the container used in a calorimetry experiment, such as a glass beaker or a boiling tube, through which a thermometer can be inserted to detect changes in temperature throughout a reaction.

This assignment also required determining the melting points of paraffin wax and stearic acid, in addition to using the cooling curve graph to determine the cooling point.

Calibration of the Thermometers

During the experiment, mercury and alcohol-based thermometers, as well as a digital thermometer and a thermal thermometer, were used. Multiple thermometers were employed to ensure the most precise readings during the calibration process and accurate data collection during the experiment.

Cold Water Calibration

Cold water calibration was performed by filling a large beaker (250 cm^3) halfway with crushed ice and topping it off with a small amount of tap water.

The crushed ice was then stirred with a glass rod for approximately 2-3 minutes before being set aside. The thermometer was then placed in the beaker, and temperature readings were taken every minute for 11 minutes. The results are recorded in the table below:

Time (min)	Temperature (°C)
0	0.0
1	0.0
2	0.0
3	0.0
4	0.0
5	0.0
6	0.0
7	0.0
8	0.0
9	0.0
10	0.0
11	0.0

Hot Water Calibration

Hot water calibration was performed by filling a beaker with 150 cm^3 of distilled water and preheating a Bunsen burner to bring the water to a boil. Once the water was boiling, the thermometer was inserted into the boiling water. Temperature readings were collected every minute for 11 minutes. The results are recorded in the table below:

Time (min)	Temperature (°C)
0	100.0
1	100.0
2	100.0
3	100.0
4	100.0
5	100.0
6	100.0
7	100.0
8	100.0
9	100.0
10	100.0
11	100.0

The thermometers were also calibrated using an infrared thermometer, which is not represented in the tables above.

Part 2: Cooling Curve Analysis

In this section of the experiment, we analyzed cooling curves using paraffin wax and stearic acid. The cooling curves helped us understand the cooling process and the effect of different materials on the rate of cooling.

Risk Assessment

Risk	Hazard	Precaution
Glassware	Breaking, Stabbing	Handle carefully
Fire	Hair getting caught or burning yourself	Tie up hair and behave appropriately

Equipment

Polystyrene cup
Ice
2x beakers
Distilled water
Ice cubes
Glass stirring rod
Bunsen burner
Gauze
Heatproof mat
Tripod
Tongs
Liquid-filled thermometer (alcohol)
Thermometers (mercury, alcohol, digital, thermal)

Method for Cooling Curve

Place 2cm of paraffin wax into a boiling tube (any less would not be enough substance to be precise, and any more would take too long to melt).
Put the boiling tube in boiling water in a beaker.
Melt the wax completely into a liquid state by heating it.
Insert the chosen thermometer into the boiling tube (ensuring it does not contact the corners or bottom for accurate readings) and record the highest temperature of the liquid Paraffin wax.
Using tongs, remove the boiling tube from the beaker and place it on a test tube rack.
Allow the paraffin wax to cool for a few minutes.
Keep a record of the wax's temperature over time (every minute) until it returns to a solid form and the thermometer reads room temperature (around 24 degrees Celsius) For Stearic acid, use this precise procedure, taking temperature readings every minute.

Cooling Explanation

Cooling will take place in a variety of methods. One approach is by latent heat, which occurs when a substance changes state, and heat energy is taken in or released into the environment. Another method is conduction, which occurs when heat energy is transported from a solid (solid Paraffin wax) to a liquid (liquid Paraffin wax) when the temperature changes, such as from 86 to 0 degrees Celsius (C). Heat energy is transferred to the cooling process through the material's surface.

Because a boiling tube has a small surface area, cooling will be affected because the substance will take longer to cool. If a beaker with a larger surface area were used instead of a boiling tube, it would cool considerably faster. In this experiment, no lid was placed on the beaker, allowing air to circulate around the substance and accelerate the cooling process. The absence of a lid also meant that air from the room could interact with the substance, causing it to cool more rapidly.

Cooling of Paraffin Wax

Time (min)	Temperature (°C)
0	86.0
1	74.0
2	67.0
3	61.5
4	57.5
5	55.0
6	53.0
7	52.5
8	52.0
9	51.5
10	51.0
11	51.0
12	51.0
13	50.5
14	50.0
15	50.0
16	49.0
17	48.0
18	47.5
19	47.0
20	46.0
21	45.5
22	45.0
23	44.0
24	43.0
25	42.5
26	41.5
27	40.5
28	40.0
29	39.0
30	38.5

Cooling of Stearic Acid

Time (min)	Temperature (°C)
0	79.0
67.0
2	61.5
3	57.5
4	55.0
5	53.0
6	52.5
7	52.0
8	51.5
9	51.0
10	51.0
11	51.0
12	50.5
13	50.0
14	50.0
15	49.0
16	48.0
17	47.5
18	47.0
19	46.0
20	45.5
21	45.0
22	44.0
23	43.0
24	42.5
25	41.5
26	40.5
27	40.0
28	39.0
29	38.5
30	38.5

Conclusion

In conclusion, this experiment aimed to analyze cooling curves of paraffin wax and stearic acid while calibrating various thermometers for precise temperature measurements. Calibration using cold and hot water provided valuable data for choosing the most accurate thermometer type.

The cooling curve analysis revealed insights into the cooling process, highlighting the significance of surface area and the absence of a lid in the cooling rate. The experiment also emphasized the importance of timely temperature readings.

If the experiment were to be conducted again, it would be crucial to improve the timing and minimize delays during temperature recording to enhance the accuracy of results.