Bio H– Basic Chemistry
Chemistry Lab Part I: Chemical Reactions
Station 1 – Chemical Reactions
Introduction
Chemical reactions occur every day all around us. A chemical reaction is a process where one type of
substance is chemically converted to another substance. The starting substances are called reactants. The
substances left at the end are called products. Often when two chemicals react, energy is either needed or
released. The energy can be in multiple forms including light and heat.
If a reaction needs energy, it might pull heat from the surroundings. This type of reaction is called
endothermic. We would notice that the beaker felt cool or colder than before the reaction. If heat is released
in order for the reaction to take place, the reaction is said to be exothermic and experimenters will notice an
increase in temperature. Watch the video below to learn more about these reactions
https://www.youtube.com/watch?t=112&v=L-G7pLufXAo
Perform the chemical reactions listed below and identify each as exothermic or endothermic.
Reaction 1 Procedure: Iron + Oxygen
1.
2.
3.
4.
Record the temperature of the thermometer sitting at room temperature.
Take a piece of steel wool. Look and feel it’s texture before soaking the steel wool.
Soak it in a 50 ml beaker, containing 25 ml of vinegar for 10 sec (be sure to time the reaction)
Squeeze the vinegar out of the steel wool, and place the steel wool in a DRY beaker so that the fold is
perpendicular to the desk surface. Gently insert the bulb of the thermometer so that it is “within the steel
wool, near the fold. Use a biuret clamp, or hold the thermometer so that it remains within the steel wool,
but is not touching the bottom of the beaker.
5. Wrap a piece of plastic wrap around the steel wool and thermometer bulb
6. While holding the thermometer, wait for 3 minutes, watching the thermometer.
7. Now record the highest temperature shown on the thermometer during the three minute period, Tf.
Data Collection:
Ti ________
Tf __________
ΔT (Change in Temp) _______
Place the steel wool used in the experiment on a piece of paper towel, and record changes in color and texture
(you may want to go back to the first station to compare your results.
Steel wool has iron as a major component. Use the website http://science.howstuffworks.com/question445.htm
to come up with the chemical reaction that has occurred.
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Bio H– Basic Chemistry
Station 2 – Chemical Reactions
Reaction 2 Procedure: Vinegar + sodium bicarbonate
1. Pour 10mL of vinegar into a 50 ml beaker and record the initial temperature (put a thermometer into the
vinegar for at least one minute, then record temperature)
2. Add a small scoop of baking soda to the vinegar (you don’t want the vinegar to overflow the beaker)
3. Keep watching the thermometer for three minutes AFTER the baking soda was added.
4. Periodically swirling the beaker. Record the lowest temperature.
5. While you wait record your observations below
Data Collection:
Ti ________
Tf __________
ΔT (Change in Temp) _______
Observations (other than temp. change) for BOTH of the above reactions:
1. What is the chemical equation that occurred?
http://staff.camas.wednet.edu/blogs/burtonscience/2012/02/09/the-chemical-formula-for-the-combinationof-vinegar-and-baking-soda/
2. Which of the reactants is an acid? Which is a base? When an acid and a base combine what general
substance is formed (besides water and, in this reaction, carbon dioxide)?
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Bio H– Basic Chemistry
Station 3 – Types of Mixtures
Introduction:
A mixture is two or more pure substances, combined in varying proportions - each retaining its own specific
properties. The components of a can be separated by physical means, i.e. without making or breaking of
chemical bonds. A homogeneous mixture has the same uniform appearance and composition throughout.
Homogeneous mixtures are also called solutions. The powder is called the solute, the liquid is called the
solvent. A heterogeneous mixture consists of visibly different substances or phases. These may also be called
suspensions. The two substances might not be obvious right after shaking the mixture. But if a suspension is
allowed to sit for a while, the substances will separate. This will not happen with a solution.
Procedure:
Put 50mL of water into each of two beakers. You have been given several grams of two different powders.
- Very carefully, place a small scoop of powder A into one of the beakers of water.
- Place a similar amount of powder B into the OTHER beaker of water.
- Stir each mixture with the stirring rod and observe what happens. Allow each to sit for a minute or two.
Record whether you saw any powder settle. Identify which mixture (A or B) is a solution and which is a
suspension.
Data Collection:
Observations for Powder A in water:
________________________________________________________________________
________________________________________________________________________
Observations for Powder B in water:
________________________________________________________________________
________________________________________________________________________
Which is the solution? ___________________________ What is your evidence?
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Bio H– Basic Chemistry
Station 4 – How Temperature Affects Chemistry
How quickly a chemical reaction takes place depends on several things: the amount of the reactants, the
presence or absence of a catalyst (something that speeds up a reaction without changing itself) and even the
temperature. In this easy little experiment we are going to compare a chemical reaction at three different
temperatures and see which works the best.
Procedure:
NOTE: Do not touch the hot plate or adjust the dials for any reason!!!
- You may need to add more ice if the ice water has all melted
1. Make sure the shade is lowered.
2. You need to “crack” the glow stick just prior to starting if you are the first group. You only need to use
one glow stick.
3. You have three beakers in front of you: Ice water, Room temp water and hot water.
4. Begin by placing the glow stick in the room temp beaker.
5. After you have observe it for 1 minute, move it to the hot water beaker for one minute
6. Record any changes.
7. Now place the glow stick in the ice water bath
8. Record any changes
9. Before moving to the next station, return the glow stick to the room temp beaker.
Data:
What change did you notice in the light sticks? Read http://www.compoundchem.com/wpcontent/uploads/2014/10/Chemistry-of-Glow-Stick-Colours-v2.1.png
Explain why the color reaction occurs. Why do you think the brightness changes? (explain this based on the
rate of the reaction).
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Bio H– Basic Chemistry
Station 5 – Fluorescence
In the beginning of lab we said that chemical reactions can give off energy. Other chemicals actually absorb
energy (either from heat or light) and then give it back out in the form of light (often a light that is a color
different from the light that is absorbed. For instance, a lot of chemicals can absorb UV light, which we can not
see, and give off visible light creating a sort of “glow” call fluorescence. In this part of the lab we are going to
test some materials to determine which have the ability to absorb UV and emit visible light.
Procedure:
1. Check this lab station for the substances that you will be testing. Record each in the table below.
2. Place four substances at a time in the box. Allow all four to sit for 15 seconds while you observe
3. Record whether the substance “glows”, or changes color (but does not glow). You should record any
other important observations
4. Repeat with each of the substances.
5. Remove everything from the box and turn off the light. Are there any other observations you’d like to
record? (hint hint….)
6. Possible substances: Laundry detergent, Fluorescent Rock, tonic water, club soda, dead glow stick,
highlighter, petroleum jelly, Irish spring soap
Read about fluorescence (see the handout) and explain why some things might fluoresce, but others don’t
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Bio H– Basic Chemistry
Data:
Substance
Before, during and after exposure to UV lightHC2H3O2
Before:
Beads
During
After:
Before:
Tonic water
During
After:
Before:
Club soda
During
Tide
After:
Before:
During
Petroleum Jelly
After:
Before:
During
Fluorite
After:
Before:
During
Dead glow stick
After:
Before:
During
Highlighter
After:
Before:
During
After:
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Bio H– Basic Chemistry
Lab Questions:
Directions: use the information in this lab AND YOUR NOTES to answer the following lab questions. DON’T
GUESS. You have the info to answer accurately; it might just take a little work.
Questions for Station 1 and 2:
1. Reactants and products:
a. What is the product of reaction 1?
b. What are the reactants of reaction 2?
2. Endothermic/Exothermic:
a. Which reaction is endothermic? How do you know?
b. Which reaction is exothermic? How do you know?
Questions for Station 3:
Powder A = corn starch
Powder B = confectioners sugar
1. What was the solvent for mixture B?
2. What was the solute for mixture B?
3. Which powder formed a solution? How do you know?
4. What term do we use to describe the mixture that didn’t form a solution?
Questions for Station 4:
1. What happened to the glow stick when you put it in cold water? Why?
2. What happened to the glow stick in the hot water? Why?
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Bio H– Basic Chemistry
Questions for Station 3:
1. List all the substances that contained fluorescent molecules:
2. Tide is trying to scam its customers! It makes clothes look like they “glow” under UV light.
a. What is the most common source of everyday UV light?
b. Tide wants people to think that the brightness of the “glowing” clothes means that the clothes are
actually _______________________.
3. What effect did the UV light have on the white beads?
CONCLUSION QUESTION: this will require some thinking and explaining, but you can do it!
Ok. Here is what we’ve learned:
1. When certain chemicals are mixed, a chemical reaction happens
2. Chemical reactions can release energy.
3. Fluorescent chemicals can absorb energy and turn it into light
4. A “dead” glow stick will glow again if it absorbs energy from UV light.
5. Chemical reactions only last for however long there are reactants. Once all the reactants have been
converted to products, the reaction ends.
6. Heat will speed up how fast reactants become products. Cold will slow down the conversion from
reactant to product.
With the above info and your brains do the following:
1. Explain how a glow stick works (no need for chemical names, but you should mention all the parts that
are necessary) to make it easier, put it in a bulleted list so you can answer step by step.
2. Explain why putting your glow stick in the freezer can extend its “life” after it is cracked.
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