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#WATER BATH BOILING POINT MEASURE HOW TO#

Place all the boiling tubes with stearic acid into a large beaker. The water temperature should rise as the stearic acid cools and it should continue to rise even as it changes state.Ī slight alternative to this experiment is to plot only the cooling curve. Use a second temperature sensor to monitor the temperature of the water. A slight modification of the experiment can yield an intriguing result: When the test tube is cooling place it in an insulated cup containing a few cm 3 of water. It can plot the temperature change on a graph and show this as it occurs. Students could be provided with another thermometer, and asked to maintain a lower temperature, say 80 ☌.Ī temperature sensor attached to a computer can be used in place of a thermometer. It is not essential that the water bath is boiling. This can be achieved by sliding the Bunsen burner aside as the boiling becomes too vigorous slide it back as the water stops boiling.

#WATER BATH BOILING POINT MEASURE HOW TO#

This presents a good opportunity to demonstrate how to maintain a steady temperature using a Bunsen burner. Remind students not to attempt to move the thermometer in the solid stearic acid, as it will break.Įnergy must be supplied to melt a solid this same energy is released when the liquid re-solidifies. Note on your results table the temperature at which you see the stearic acid begin to solidify.Īpparatus set-up for the melting and freezing stearic acid experiment Teaching notes Record the temperature every minute as the stearic acid cools down until it reaches about 50˚C. Use the clamp stand to lift the tube from the hot water.Note on your results table the point at which you see the solid start to melt. Using a suitable results table, record the temperature of the stearic acid every minute until it reaches about 70˚C.Keep the water boiling, but not boiling vigorously.

Set up the apparatus as shown in the diagram and start the timer.Heat it on a tripod and gauze until the water just starts to boil.Put about 150 cm 3 water into the beaker.Have enough to quarter fill a boiling tube for each student The stearic acid in this practical can be used again and again.

Stearic acid (octadecanoic acid), CH 3(CH 2) 16COOH(s) – see CLEAPSS Hazcard HC038b.

Read our standard health and safety guidance.

The stearic acid can then be stored in the boiling tubes and recycled several times.

If, after the practical, the boiling tubes are left containing both the stearic acid and the thermometer, immerse all the boiling tubes in hot water to remove the thermometers.

If data-loggers are being used then students will need another activity to be doing alongside the experiment. Students can begin by simply recording their data but, once they get the hang of what they are doing, most should be able to plot the graph at the same time as taking readings. This practical takes quite a long time to carry out. This experiment could also be done using data-logging equipment The students will take the temperature of stearic acid at regular intervals as they heat and cool it. They can observe the melting and freezing points of the acid and can plot a graph.

RSC Yusuf Hamied Inspirational Science Programme.

Introductory maths for higher education.

The physics of restoration and conservation.