Goals: In this lab, students will study different aspects of enzyme activity by doing the following: ... 3. CAUTION: The water bath contains hot water. Steam will burn. 4. Be careful when using test tubes in hot water bath. Use a test tube holder. La
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Idea Transcript
Name:_______________________
Lab: Enthalpy and Entropy Purpose: To observe and measure energy changes during the formation of a solution and to describe/explain these changes in terms of entropy and enthalpy. Materials: Thermometer Beaker Plastic spoonSolid NaCl, NH4Cl, CaCl2
Water Stirring rod
Procedure: 1. Place two level spoonfuls of water in a beaker and measure the temperature (T1) of the water. Record in data table. 2. Add one level spoonful of solid NaCl to the cup. Stir gently and measure the highest or lowest temperature (T2). Record. 3. Repeat the experiment two more times using NH4Cl and CaCl2. Data Table:
(change) = final - initial
Mixture
T1
T2
T
Endothermic or Exothermic
H
S
G=
H -T S
NaCl + H2O NH4Cl + H2O CaCl2 + H2O
For the last 3 columns, just tell whether the value would be (+) or (-).
H = enthalpy = heat. If the endothermic, took in heat (H2 is higher than H1 = H that is positive number) If exothermic, lost heat (H2 is lower than H1 = H that is negative number) S = entropy = disorder. The more disorganized the system gets, the larger the entropy number (+) (Lots of order, low entropy) = solids liquids gases (lots of disorder, high entropy)
Analyze: When sodium dissolves in water, the ions dissociate. NaCl(s) Na+ + ClWrite the ionic equations, similar to the one above, that describes how NH4Cl and CaCl2 each dissociate as they dissolve in water. Include heat as a reactant or product in each equation. 1.