Shenzhen University Physical Chemistry Experiment Report

Shenzhen University Physical Chemistry Experiment Report

　

Experimenter: Zhang Zike, Liu Kaixin Experimental time: 2000/4/17

Temperature: 21.7 °C Atmospheric pressure: 101.7 kPa

Experiment 1 Assembly and performance test of constant temperature water bath

　

1 purpose requirement

Understand the structure of thermostatic water bath and its construction principle, learn the assembly technology of constant temperature water bath; measure the sensitivity curve of constant temperature water bath; master the adjustment technology and correct use method of Beckmann thermometer.

2 instruments and reagents

5 liter beaker Beckman thermometer precision thermometer heater

Mercury contact thermometer relay stirrer transformer

3 data processing:

Graph:

4 thinking:

What are the main factors affecting the sensitivity of the thermostatic bath?

Answer: The factors affecting sensitivity are related to the working medium, temperature sensing element, stirring speed, heater power, and physical properties of the relay. If the heater power is too large or too low, it is difficult to control the temperature of the water bath so that its temperature fluctuates greatly above and below the set temperature, and its sensitivity is low; if the stirring speed is high or low, or is always too low, the constant temperature water bath The temperature fluctuates up and down at the set temperature, and the measured sensitivity is low. If the accuracy of the Beckman thermometer is low, the difference in temperature change recorded at different times is large, that is, the temperature of the water bath fluctuates greatly at the set temperature, and the sensitivity is low. Similarly, the temperature sensing effect of the contact thermometer is poor. When the temperature is higher than the set temperature, the heater does not stop heating, so that the bath temperature drops slowly, so that the recording bath temperature fluctuates greatly at the set temperature in different time, and the measured sensitivity is low.

What measures should be taken to improve the temperature control accuracy of the constant temperature bath?

Answer: To increase the sensitivity of the constant temperature bath, use a moderately sized heater, a high-precision Beckman thermometer contact thermometer, and a stirrer with a mercury thermometer. The stirring speed should be fixed at a moderate value, and at the same time according to the constant temperature. Range Select the appropriate working medium.