Real Lab Procedure:
- Take about 25ml of distilled water in a boiling tube and add 2-3 small pieces of pumice stone.
- Close the mouth of the boiling tube with a rubber cork that has two bores and clamp it with the stand.
- Introduce a thermometer (temperature range -10 to 110°C) in one bore of the cork of the boiling tube. Keep the bulb of the thermometer about 3-5 cm above the surface of the water.
- Then introduce one end of a delivery tube in the second bore of the cork.
- Place a 250ml beaker below the second end of the delivery tube to collect the condensed water.
- Heat the boiling tube gently, preferably by rotating the flame.
- Note the temperature (t1) when the water starts boiling.
- Continue to heat the water till the temperature becomes constant, and the water remains boiling. Note the constant temperature (t2).
- Record your observations in tabular form.
Note: Pieces of pumice stone are added to water before heating to avoid bumping of liquid when the temperature rises. When water boils it releases energy as bubbles. If the bubbles do not form, the water can super heat and possibly explode. This could happen if the container is very clean and there is no means for the formation of bubbles. Adding pieces of rough stone gives lots of surface area for bubbles to form and release the energy gradually.
- You can select the different conditions from ‘Boiling point of water’ drop down list.
- You can select the pressure/impure sample from ‘Select the pressure/impure samples’ drop down list.
- To put pumice stones into the test tube containing water, drag the spatula towards the test tube.
- To close the test tube, drag the double bored cork towards it.
- To insert the thermometer through one hole of the cork, drag the thermometer towards the test tube.
- To insert the delivery tube through the other hole of the cork, drag the delivery tube towards the test tube.
- To turn on the burner, click on the knob of the burner.
- You can see the zoomed view of the thermometer by clicking on the ‘Show zoom’ check box.
- You can see the temperature variation on the left side menu , at a particular temperature the water starts boiling and this constant temperature is the boiling point.
- Click on the ‘Reset’ button to redo the experiment.
Note: Click on the ‘HELP’ button to see the instructions.
Record observations in the table given below:
|Temperature when the water
||Boiling point of water
|Starts boiling t1 (in °C)
||Continue to boil (Stationary temperature) t2 (in °C)
||(t1 + t2)/2 (in °C)
The boiling point of water =_______°C
- The bulb of the thermometer should be kept about 4-5 cm above the surface of water.
- Pieces of pumice stone should be added to water before heating to avoid bumping.
- Heating of water should be done by rotating the flame.
- Note temperature by keeping your eyes in line with the level of mercury.