Name _______________
Period _________________
Pre-Lab:
Definitions:
A system is defined as what is being studied, i.e. a change of phase or a chemical reaction.
The surroundings is anything, often air, water and/or glassware e.g. a beaker, that accepts or releases energy
from or to the system e. g. heat.

T means a change in temperature from initial temperature (1) to final temperature (2). In these experiments, you
will use the largest temperature differences for the T calculations.
An observation is a statement of fact, based on sensory data. A statement such as “the liquid is clear and
colorless” is an observation. List 2 examples of observations, you might see in a chemistry lab.
______________________________________________________________________
An interpretation or a conclusion is a judgment or opinion about what is observed. It would be an
interpretation to say - "The clear colorless liquid is water" based on observations alone.
Given a choice of 2 terms, circle the correct answer or fill in the blanks.
1. Define quantitative observation ________________________________________
2. Define qualitative observation ___________________________________________
3. List different forms of energy. ________________________________________
4. If a substance feels cold, is energy absorbed by the system or released by the system?
5. If a substance feels warm, is energy absorbed by the system or released by the system?
6. If the original temperature is 20.0°C and your final temperature is 15.0°C, what is T? _______
7. Is energy being released or absorbed by the system?
8. If the original temperature is 20.0°C and your final temperature is 25.0°C, what is T? _______
9. Is energy being released or absorbed by the system?
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10. Discuss in your group and list examples of indicators that a chemical reaction has occurred?
_____________________________________________________________________
OBSERVING CHEMICAL REACTIONS
INTRODUCTION:
PURPOSE: The purpose of these experiments is to observe chemicals and chemical changes, both qualitatively and quantitatively.
Exp. 1. Citric Acid + Baking Soda
H3C6H5O7(aq) +

 carbon dioxide, water, and sodium citrate
3 NaHCO3(s) 
 3 CO2(g) + 3 H2O(aq) + Na3C6H5O7(aq)
Materials: 250 ml beaker, 20 ml 1.5 M citric acid, approximately 3.0 g baking soda in a small vial, 25.0 ml graduated cylinder, stir
rod, Styrofoam cup, and thermometer.
Experiment 1:
a. Write the reaction between Baking Soda and Citric Acid in your lab book.
b. Describe the dry baking soda in detail and record observations in your Lab book.
c. Measure approximately 25.0 – 30.0 ml of 1.50 M citric acid solution. Record the exact amount of citric acid in the data table,
then pour into a 250 ml beaker. Have a vial of baking soda ready to add. DO NOT ADD YET.
d. Place the thermometer into the 25.0 – 30.0 ml of citric acid solution which is in the 250 ml beaker. RECORD INITIAL
TEMPERATURE OF THE CITRIC ACID FIRST. Place beaker into Styrofoam cup. Then, ADD THE BAKING SODA 1-2 scoops.
e. After 3 minutes, record the Temperature for your final data point.
f. Dispose of the reaction products by rinsing them down the sink with water.
g. Use the initial and final temperatures to get the temperature difference for T to use in your calculation for Q.
Experiment 2:
Al(s) + CuCl2(aq)

Cu(s) + AlCl3(aq)
Materials: Approximately1/3 of the blue-green crystals, copper (II) chloride crystals in a small vial, approximately 1.5 cm square
piece of Aluminum foil, 100 ml or 150 ml beaker, water, 25.0 ml graduated cylinder, stir rod, Styrofoam cup, thermometer.
a.
b.
c.
d.
e.
f.
Write the reaction between Aluminum and Copper (II) Chloride in your lab book.
Describe the dry copper (II) chloride crystals in detail and record observations in your lab book.
Set the 100 ml or 150 ml beaker into a styrofoam cup as an insulator.
Add approximately 25 ml of tap water to the beaker. Record exact amount of water, after measuring in a graduated cylinder.
Without stirring, add approximately 1/3 of the blue-green crystals (in the vial) to the water. This is copper (II) chloride Observe
both the crystals and the water and record observations in the Data Table.
After observation, stir the mixture with the glass rod until the crystals completely disappear and the solution is homogeneous.
Record observations in the Lab book.
a.
b.
c.
d.
e.
f.
Place thermometer into your homogeneous copper (II) chloride solution.
Tear the aluminum foil into small pieces. Do not add it yet.
Record the temperature of just the copper (II) chloride solution.
After recording temperature, add the loosely torn aluminum foil quickly all at once to the copper (II) chloride solution.
Continuously stir the mixture with glass stir rod not the thermometer. Record temperature every 30 seconds for 3
minutes. Record any observations in addition to the temperatures into your data table.
Pour the waste solution into the waste beaker for your instructor to dispose of safely. (Large beaker
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in fume hood labeled waste). Rinse and clean all equipment. You will have to use a paper towel to remove the solid waste
into the trash can.
All calculations are based on q = m Cp T
Show all work for calculations.
Use Cp H2O = 4.18 J/g C for both reactions i.e assume solutions have the same Cp as water.
Use the 1.0 g = 1.0 ml for the mass of all liquids, CuCl2 solution and citric acid.
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