Temperature and Phase Changes In this exercise, you will makeobservations of the phase changes of water (H 2 O). You willmeasure temperature and create a heating curve to determine themelting point and boiling point of water. 1. Gather the 250-mLbeaker, approximately 150 mL of crushed ice, a watch or timer, thethermometer, burner stand, burner fuel, and matches. Note: Largeice cubes may be crushed by placing them in a large plastic bag,placing the bag on a durable surface, and breaking the pieces apartwith a hammer or other heavy object. 2. Fill the beaker to aboutthe 150-mL line with crushed ice. 3. Place the thermometer in thecenter of the ice. Do not allow the thermometer to touch the sidesor bottom of the beaker. 4. After holding the thermometer in theice for about a minute, note the time and record temperature at 0minutes in Data Table 2 of your Lab Report Assistant .Additionally, record your observations about the state of matter(solid, liquid, or gas) of the water in Data Table 2 . 5. Uncap theburner fuel, light the wick with a match or lighter, and place thefuel under the stand on a pie pan. Burner setup. Note that theflame is blue which is sometimes difficult to see. 6. Place thebeaker on the burner stand. Keep holding the thermometer in themiddle of the ice. 7. Start the timer and begin taking temperatureand observation readings every minute, recording your findings inData Table 2 . Note: It is important that you record both thetemperature AND the state or states of matter present every minutethroughout the experiment. 8. Gently stir the ice with thethermometer as it heats. www.HOLscience.com 13 ©Hands-On Labs, Inc.Experiment Liquids and Solids 9. Continue to stir the ice or waterand record temperature and observations every minute until thewater has boiled for 5 minutes . Do not allow the thermometer torest on the glass of the beaker. 10. Extinguish the burner fuel bylightly placing its cap over the flame; do not tighten cap untilthe burner fuel container has fully cooled. 11. Thoroughly wash andrinse the equipment for future use. Questions: A. Using thetemperature data recorded in Data Table 2 , create a heating curve.● Plot time (minutes) on the x-axis (horizontal axis) andtemperature (°C) on the y-axis (vertical axis). Connect the plottedpoints with a line. ● Label the heating curve to show each phase ofmatter (solid, solid + liquid, liquid, liquid + gas). ● Label themelting point and boiling point on the heating curve. Note: Anexample heating curve is given in Figure 6 of the Background B. Arethere parts of the curve with positive slopes and parts that areflat (slope of zero)? What states of matter are present when theslope of the heating curve is positive and what states of matterare present when the slope is zero or close to zero? C. Describethe key characteristics for the three states of matter. D. Definethe melting point. What was the observed melting point ofwater?

E. Define boiling point. What was the observed boiling point ofwater?

F. What happens to heat energy when it is not increasing thetemperature of the substance in the beaker? Use your heating curveto explain your answer. G. Was temperature perfectly constantduring your test while the water was melting and while it wasboiling? Explain why or why not.

H. The published melting point of H 2 O is 0°C, and thepublished boiling point is 100°C. Why may you have found differentvalues?

I. Use the following information to determine if theintermolecular forces of isopropyl alcohol are greater or weakerthan the intermolecular forces of water. Explain your answer. Themelting point of isopropyl alcohol (rubbing alcohol, C 3 H 8 O) isabout -90 °C and the boiling point is about 82 °C