Name I

Your Name
Chem 1151 Section 3
Endothermic and Exothermic Reactions
Date of Experiment
Your Lab Partner’s Name
The purpose of this experiment is study the energy associated with two
chemical reactions. By measuring the increase or decrease of the
temperature of the reaction solution, it was determined that one chemical
reaction absorbed heat (endothermic) and the other released heat
(exothermic). A handheld Palm unit and temperature probe were used to
measure and record the temperature change of the reaction solution. Other
changes associated with the chemical reactions were observed.
Each lab report is worth 10 points except
 experiments carried out on the same day (e.g. Expts 1A +1B are
worth 10 altogether; same for Expts 8A+8B and Expts 9A+9B) and
 experiments carried out over two weeks (e.g. Expt 11 is worth 20 )
10% of the lab report is assigned to the Pre-Lab Assignment which must be
completed before the experiment is started. The Pre-Lab assignment
consists of the Pre-Lab Assignment published in the lab manual and
preparing your lab notebook with the title, date and purpose of the
experiment, and tables for data entry. This assignment should be completed
in your lab notebook and you need not submit it in your lab report. When
you arrive in lab, your TA will check your lab notebook and record whether
the Pre-Lab is done.
DATA (Present your raw data in prepared tables; each table needs a
number, title and units. Any graphs and computer printouts you
printed in lab should be included in this section.)
Table 1
temperature, t2
temperature, t1
change, Δt
Initial and Final Temperatures of Reaction Solutions
Part I
Citric Acid +
Baking Soda
13.40 oC
Part II
HCl + Mg
18.55 oC
21.12 oC
-5.15 oC
25.05 oC
OBSERVATIONS (note evidence of a chemical reaction (temperature
change, evolution of a gas, precipitation, neutralization), physical
properties (like color, state of matter) and changes in physical
Part I: Bubbles were given off showing that a gas was produced when
reactants were mixed. The baking soda disappeared. The reaction container
cooled down.
Part II: Mg metal dissolved. Bubbles were given off. The reaction
container warmed up.
III. CALCULATIONS AND RESULTS (This is the section where you
show how you treated your raw data. Include one sample of each type of
calculation. If you analyzed your raw data on Excel, describe the x and y
variables, include the equation you used, attach the spreadsheet and show
how you calculated the desired final values. Your final values should have
the correct number of significant figures and units.)
The change in temperature is Δt = t2 - t1 = 13.40-18.55 = -5.15 oC for Part I.
Repeat this calculation for Part II.
Two graphs (one for each reaction) should be included in this section.
where you interpret your data and answer any post-lab questions at the end
of the experiment.)
The reaction in Part I is endothermic because it absorbed heat from the
reaction solution causing the solution to cool down. This reaction has a
negative Δt value.
The reaction in Part II is exothermic because it released heat to the reaction
solution causing the solution to warm up. This reaction has a positive Δt
A reaction that is taking place may give off a gas, warm up or cool down,
dissolve a solid, change color, form a solid.
The reaction in Part II occurred faster because it reached its final
temperature, t2, faster.