Experiment: Heating Curve for Water
Objective: To construct and interpret a heating curve for water.
Materials:
250 ml beaker
200 ml deionized water (tap water will work reasonably well if deionized is not available)
Ice
Hot plate with stirring capability
Teflon stir bar
Glass stir rod
Thermometer or other temperature measuring device (i.e. thermoprobe or thermister)
Rubber stopper with single hole – stopper should be slit from hole to outer edge
Ring stand with ring stand clamp
Stop watch
Safety goggles
Procedure: Place about 150 ml deionized water into the 250 ml beaker and add enough
ice to form a slush. If ice cubes are used, add sufficient ice to
increase the volume by about 50 ml. Allow the ice-water mixture
to come to thermal equilibrium which should take about 5
minutes. Occasional stirring with a glass stir rod will accelerate
the equilibrium. Carefully slide the thermometer through the slit
hole in the stopper such that about one third of the thermometer
extends through the top of the stopper. Attach the ring stand
clamp near the top of the ring stand. Using the ring stand clamp,
clamp the rubber stopper holding the thermometer so that the
thermometer is about 15 cm above the base of the stand. Place
the hot plate on top of the ring stand. See Figure 1. Plug in the
hot plate and turn the heat on. Set the hot plate dial to a
middle heat setting. Allow the hot plate to warm for 5 minutes.
Place a Teflon stir bar in the water/ice beaker. Place the beaker
on the hot plate and turn the stirrer dial until the liquid is stirred
without splashing. Lower the ring clamp until the thermometer
bulb is immersed in the water. Make sure that the stir bar does
not hit the thermometer and that the thermometer is not touching
any part of the beaker. Record the temperature of the water at 60
second intervals. A stop watch or wrist watch with a second
hand can be used for recording the time. Continue recording the
temperature until a rapid boil is observed. Obtain five additional
readings
beyond this point. Turn off the hot plate and stirring
Figure 1
function when data recording is complete. Allow the beaker to cool before attempting to
remove it from the hot plate.