Experiment report.
Experiment name: Melting point determination.
First, the purpose of the experiment.
1.Master the basic principles and methods of melting point determination;
2.Learn to use a melting point tester to measure the melting point of a substance;
3.Understand the relationship between the melting point of a substance and the purity of a substance.
Second, the principle of experiment.
Melting point refers to the temperature at which a substance changes from a solid state to a liquid state, and is a physical property of a substance. Melting point determination is determined by observing the change in temperature of a substance during heating. In the experiment, we use a melting point tester to determine the melting point of a substance by converting the temperature change into an electrical signal using the thermocouple principle, and recording the temperature curve over time through a recorder.
3. Experimental procedures.
1.Sample preparation: accurately weigh the appropriate amount of the substance to be measured, grind and dry, and then put it into the sample tube;
2.Instrument preheating: Turn on the power of the melting point tester and preheat the instrument to the required temperature;
3.Start the measurement: Place the sample tube in the furnace of the melting point tester and observe and record the temperature change with time;
4.Result processing: Determine the melting point of the substance based on the recorded temperature change curve.
Fourth, the experimental results and analysis.
The following are the melting point data of several substances determined in this experiment:
Name of substance |Melting point ( ) Purity (%)
Sucrose | 185.5 | 99.5 |
NaCl | 801.7 | 99.0 |
Copper sulphate | 257.5 | 98.5 |
Absolute ethanol | 114.1 | 99.9 |
n-hexane | 129.8 | 99.8 |
Based on the experimental data, we can draw the following conclusions:
1.The melting point of different substances is different, and the melting point of the same substance at different purities is also different;
2.As the purity of the substance increases, its melting point also increases;
3.By comparing the melting point of the experimental determination with the literature value, the purity of the sample and the presence of impurities can be determined.
5. Experimental conclusions.
Through this experiment, we have mastered the basic principles and methods of melting point determination, and learned to use a melting point tester to measure the melting point of substances. The experimental results show that the purity of the substance has a significant effect on its melting point. In practical application, the purity and whether it contains impurities can be judged by measuring the melting point of the substance, which provides strong support for the quality control and research of the substance.