The Melting of Solids Group member names: _____ _____________________ ________________________ ___
Period: ________
Overview: In today’s lab you will measure and compare the melting/freezing curve of two compounds: naphthalene (used in mothballs) and candle wax. You will conduct the experiment on both liquids, recording your observations on this data sheet. Once graded and returned to you, you will prepare a detailed lab report as part of your fourth term grade. Rather than writing and graphing each data point (like you did with the boiling water lab), you will use the Texas Instrument’s Nspire handheld units along with a Vernier Temperature Probe. You will set up the software for data collection and safely handle each of the two materials. Although your instructor will use the digital overhead projector to help step you along the experiment, you are free to work at your own pace.
SAFETY:1 - Goggles must be worn by each member of your group or your grade will be significantly reduced! ______
FIRST 2 – All test tubes containing liquid must be held by a clamp. The liquids can cause serious burns. ______
3 – Rubber stoppers must be on all test tubes unless they are clamped in the test stand. ______
4 - Do not press rubber stoppers into the tube – stuck stoppers risk splashes. ______
INITIAL ABOVE
Pre-lab questions (You must answer these questions before obtaining materials):
1. Can a frozen material be too hot to touch? Explain why. ________________________________________________________________
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2. Is the process of melting endothermic or exothermic? Explain why. __________________________________________________
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3. Is the process of freezing endothermic or exothermic? Explain why. __________________________________________________
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4. What kind of material has a definite, specific melting point (Circle one): crystalline / amorphous
5. What kind of material softens before it liquefies over a temperature range (circle one): crystalline / amorphous
Procedures:
TI Nspire Number: _____________
Set up Equipment
1 - Obtain the following: TI-Nspire, temperature probe, easy-link, support stand with 2 utility clamps and a ring, and a piece of steel wool, and a cup of ice water .
2 - Secure the probe to the top utility clamp and place the cup into the ring at the bottom.
3- Power up the N-Spire. Check battery icon on the upper right and change batteries if necessary.
4 - Press home and press [6] (new document). Move the curser right to highlight [No] then press [enter].
5 – Plug the temperature probe into the Easy Link then plug the Easy Link into the Nspire.
6 – “Data & Statistics” should be highlighted. Press [enter]
7 – Set data collection by pressing [menu], [1] (Experiment), [3] (Set up Collection), [1] (Time Graph).
8 – Configure Collection: Time between Samples [2], curser down, [600] [enter]
9 – Select the graph by pressing [ctrl] [tab] (the meter will shade grey), [menu]
10 – Set the Window/zoom by pressing [5], [1] (window settings).
11 – Window Settings: xMin [0], down, xMax [600], down yMin [20], down, yMax[100], [enter]
Data Collection
12- Using a test tube clamp, obtain a hot liquid sample: What material do you have? _______________________
13- Begin the Npire data collection: switch to meter [ctrl], [tab], [enter]. What temperature is the probe? __________
14 – Place the sample tube in the second utility clamp. Remove the stopper placing it upside down on the stand.
15 – Move the clamps so that the tip of the probe is about 1 inch into the liquid.
?? How many seconds between points? _______ How long before the probe reached liquid temperature? ____________
16 – Before the liquid begins to freeze, raise the ice water cup so that it immerses the liquid portion of the test tube.
The Melting of Solids – page 2
17- Describe what you observed when you placed the probe into the tube: _______________________________________________
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18 - Once the tube has frozen. press [enter] to stop collection. Twist the probe out of the solid and clean it with steel wool. Place the stopper gently into the tube and return the tube it to your instructor.
19 - Sketch the Nspire data curve below on the left. Include both time and temperature for key points of the curve.
Material: _______ Material: _________
20 – Once you have the above graph drawn, using a test tube clamp, obtain a hot liquid sample:
What material do you have? ______________________
21 – Press [enter] to begin a new run. Press [enter] to store the old run, press [enter] to select OK.
22 – Place the sample tube in the second utility clamp. Remove the stopper placing it upside down on the stand.
23 – Move the clamps so that the tip of the probe is about 1 inch into the liquid.
?? How many seconds between points? _______ How long before the probe reached liquid temperature? ____________
24 – Before the liquid begins to freeze, raise the ice water cup so that it immerses the liquid portion of the test tube.
25 - Once the tube has frozen. press [enter] to stop collection. Twist the probe out of the solid and clean it with steel wool. Place the stopper gently into the tube and return the tube it to your instructor.
26 - Sketch the Nspire data curve on the right above. Include both time and temperature for key points of the curve.
27 –Close the meter by pressing [tab] [tab] highlighting the x, then press [enter].
28 - Over lay the two curves on the graph by pressing [menu], [2] (plot properties), [6] (add Y Variable), [enter].
29 – Show this overlay graphs to you instructor for approval:
Instructor approval: __________________
Post lab questions:
1. The wax appeared to be (circle one): crystalline / amorphous
2. Identify melting point or softening range for the candle wax: ____________________________________________________________
3. The naphthalene appeared to be (circle one): crystalline / amorphous
4. Identify the naphthalene melting point or softening range: ______________________________________________________________
5. Which might cause a more severe burn if spilled on the skin? Explain why. ____________________________________________
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6. What is the independent variable in this experiment? ______________________________
7. What is the dependent variable in this experiment? _________________________________
8. Name another independent variable in this experiment. ___________________________
9. Explain why the temperature/time curve is not linear as heat is removed from each sample. Under what circumstances would this curve be linear?
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