Heat Lab

This lab will go in your lab book. Follow the directions below to complete the lab.

Purpose (put into lab book)

The purpose of this lab is to determine the relationship between the length of a piece of magnesium and the amount of heat produced by the reaction it has with hydrochloric acid.

Background (summarize in lab book)

Chemical reactions can produce heat or absorb heat during the reaction. A reaction in which heat is produced is called exothermic. A reaction in which energy is absorbed is called endothermic. The reaction you will perform today between magnesium and hydrochloric acid is an exothermic reaction.
In order to try and measure the heat that is produced, we are going to allow the water in the acid to absorb this heat and as a result we will see an increase in temperature as the heat is absorbed. This hydrochloric acid is dilute, therefore is mainly water. We can use then the specific heat of water in this calculation. As the heat is generated, we have to be careful to make sure that all the heat is absorbed by the water and not by any surroundings. We will be using what is known as a calorimeter, which is a closed, insulated container in which the chemical reaction will take place. This is made of styrofoam, which is an insulator, and will help to trap the heat inside.
You will be using the heat formula. Write this formula in your background and list what each variable represents.
We are measuring the change in temperature of the acid. Therefore, the mass used in this formula is the mass of the acid that you use each trial. Remember this acid is diluted and mostly water, so we can say that the volume in mL is equal to the mass in g.

Hypothesis (answer in a complete sentence in lab book)

What do you think will happen to the amount of heat produced as the length of magnesium reacted increases?
What graph type do you think you will get when you graph energy (y) vs length (x)?

Procedure (summarize in lab book)

Cut the magnesium ribbon into pieces from exactly 1 cm to 5 cm in length.
Measure the out 10 mL of hydrochloric acid.
Pour acid into the calorimeter and measure the original temperature.
Add a piece of ribbon and get the highest temperature using the statistics feature on LoggerPro.
Repeat with each piece of Mg ribbon getting new acid each time.

Data (copy data table into lab book, do NOT draw the pictures, they are there for you to read the measurement from)

Mg length

(cm)

Picture of LoggerPro graph that plotted the temperature as time went on. The first plateau represents the reading of the initial temperature of the acid. The rest of the graph shows the increase in temperature as the Mg was reacting with the acid.

(^oC)

(Use the picture to the left to determine the initial temperature of the acid, this is the minimum temperature)

(^oC)

(Use the picture to determine the max temperature as the Mg was reacting and record it in this data column below)

delta T

(^oC)

Energy

(J)

Calculations (show all your calculations for calculating Q for each piece of Mg in this section of your lab book)

Graph (sketch in lab book)

Using this graphing program, generate a graph of energy (y) vs. length (x). You may NOT graph this relationship by hand. It is necessary to have an equation for the line.
Sketch the graph from the graphing program in your lab notebook making sure you include all the necessary parts (title, labels and numbers on axes, best fit line).
Identify the graph type and include the equation of your line.

Conclusion (write as three paragraphs in lab book)

P #1 - Restate the purpose and describe what the procedure was.
P #2 - State what you have learned (based on the purpose, hypothesis, and graph). Was your hypothesis correct? State the graph type and equation.
P #3 - Discuss any errors that could have affected the data and suggest how to fix them. (This is easy, think about the heat you were trying to measure)

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