LAB A-1 DETERMINATION OF THE HEAT OF FUSION OF WATER

PROCEDURE:
	1- Weigh a beaker
	2- Place 200 mL of water in the beaker and weigh it
	3- Record the temperature of the water
	4- Take an ice cube and place it in the water.  Gently stir
	   the ice water with a thermometer.
	5- Record the temperature of the ice water every 30 seconds
	   until the ice melts.
	6- Weigh the beaker and water {after the ice has melted}

CALCULATIONS:
	1- Determine the weight of the water.
	2- Determine the weight of the ice cube.
	3- Determine the change in temperature {temp of step 6 minus
        step 3}
	4- Determine the number of calories that the water gave the
	   ice cube using the formula Q=CM delta T.
	5- Determine the heat of fusion of ice using the formula
	   Q=HfM.

GRAPHS:
	Graph the results of procedure 5.

QUESTIONS:
	1- What is water?
	2- What is ice?
	3- What is a calorie?
	4- What is a phase diagram?


                    SAMPLE LABORATORY WRITE-UP

                                            Tommy Smith 1-19
                                            Partner: B. Wilson
                                            2/30/1996


TITLE: Determination of the heat of fusion of water

PURPOSE:  We are to determine experimentally the heat of fusion
  of water by following a prescribed procedure.

DATA:
	Weights :                     Temperatures :
                            	                      INITIAL       30C
	beaker            	      100G     30sec        29C
 	beaker + water            300G     60sec        28C
       beaker + water +ice	       320G     90sec        27.5C
	   		     120sec       24.7C
			     150sec       23.4C
			     180sec       23.1C
			     210sec       22.4C

CALCULATIONS:
	1.  300G  (wt. of beaker + water) 2. 320G (beaker+water+ice)
	   -100G  (wt. of beaker)            300G (beaker + water)
   	    200G  wt. of water                20G  wt of ice
	
	3.  30.0 C initial temp    4. Q=C M delta T      5. Q=H M
 	   -22.4 C final temp         Q=(1)(200)(76)     1520=(H)(20)
	    7.6 C change temp        Q=1520 calories       H= 76cal/g


QUESTIONS:
	1- What is water? Water is a compound consisting of 2
	   hydrogen atoms polar covalently bonded to 1 atom of
	   oxygen existing in a liquid phase.
	2- What is ice? Ice is a solid phase of water.
	3- What is a calorie? A calorie is the amount of heat
	   required to change the temperature of 1 gram of water 1
       degree centigrade.
 	4- What is a phase diagram? A phase diagram is a graph
	   showing the three states of matter and their two phase
	   changes.

GRAPH: NEXT PAGE

CONCLUSION:
	WHAT:  In our experiment 20g of ice lowered the temperature
	  of 200g of water 7.6C.  A heat of fusion of ice was
	  calculated to be 76cal/g.
	WHY:   All matter is made up of molecules that are in
	  motion.  Molecular motion consists of vibrational,
	  rotational, and translational, in a solid mainly
	  vibrational motion exists with the molecules having a
	  strong attraction for one another.  A liquid has a
	  higher energy contained within it so that the
	  molecules are further apart and have vibrational and
	  rotational energy.  When a solid is heated its
	  temperature will rise until it reaches its melting
	  point.  Energy that is supplied at this point will go
	  into performing a phase change and the temperature
	  will not rise until all of the solid changes to a
	  liquid.  This energy that causes the phase change of
	  a solid to a liquid is called the heat of fusion.
 	RELATE:  On page 18 of the book a calorie is defined as
	  the amount of heat required to change the
	  temperature of 1 gram of water 1 degree celsius.
	  On page 21 of the module the heat of fusion of
	  water has a value of 80 cal/g and is defined as the
	  amount of heat needed to change 1 gram of water
	  from a solid to a liquid. 
	ERRORS:  My partner Rufus spilled a few drops of water out
	  of the beaker before he weighed it.
                        
       		 %error= 80-76/80 x 100 = 5%

	  This 5% error could have come in part by the spillage
	  mentioned above, and due to the fact that thermometer
	  was marked off in 2 degree increments.  Accuracy in
	  making temperature measurements could not be
	  maintained between increments.