Bruno 1
1/28/10
Are You Working??
Teacher Instructions (best for 3rd-6th grade students)
When Alka-Seltzer reacts with water, a fizzing can be observed. These bubbles are caused by a chemical reaction that produces carbon dioxide (CO2 ) gas. The gas enters into the glove attached to the bottle, and the gas exerts a force on the glove, inflating it. This transfers energy from one physical system to another, resulting in work. Many variables such as concentration and temperature can affect the amount of work being done within this system.
Key Terms:
A Chemical reaction is a reaction in which a substance is changed into one or more new substances.
Work is the transfer of energy from one physical system to another. Work is most often observed when a force moves an object in the direction of the force.
Concentration is the amount of something within a solution or particular volume.
Instructions:
1)Prep
For every group of three students, fill a small cup with water. For a third of these groups, have ½ a tablespoon of yeast and one tablespoon of sugar prepared
2)Using the colors of their safety glasses, divide the students into groups of three.
One third of these groups will each be given a 20 oz coke bottle or any other bottle design (just as long as each group has the same size and shape bottle), a glove (balloons can be used if none of the students are allergic to latex), a rubber band, one cup of water, a Kim Wipe, and two Alka-Seltzer tablets.
Another third of the groups will be given the same material as above, excluding the Alka-Seltzer tablets.
The final third of the room will be given a glove, a bottle, a rubber band, one cup of water, ½ a tablespoon of yeast, and one tablespoon of sugar.
3)In front of the class, you will do the activity while the kids follow along. Present the activity with the Alka-Seltzer, and simply tell the children without Alka-Seltzer to mix the items that they were given inside the coke bottle. To accelerate the process, have the groups using yeast put their bottles on a heating pad.
4)Tell the groups to raise their hands when their glove begins to fill with gas.
5)While you wait for the results, discuss the chemical reaction and the work that has been observed with the demo bottle containing the Alka-Seltzer.
6) Once, the rates of the reactions have become apparent, compare and discuss.
7)Introduce the affects of concentration on chemical reactions.
8) Give all of the groups another small cup of water, a glove, a bottle, a rubber band, and a Kim Wipe. Give one third of the groups two Alka-Seltzer tablets, another third four tablets, and the last third six tablets.
9)After hypothesizing the results, have the groups repeat the activity.
10)Compare the rates of the reactions with the varying concentrations.
11)Repeat the activity again but with temperature as the varying variable.
12)Using a constant of two Alka-Seltzer tablets, have one third do the activity at room temperature, another third on a heating pad, and the last third in a bucket of ice.
13)Once again, record the rates and compare and discuss.
14)If there is time, discuss the experimental process and the error of this experiment.
15)For clean up, everything is safe to pour down the drain.
Further Experiments/Discussion:
Have the kids brainstorm about what other substances would have a chemical reaction and do work. Have the students think of other potential variables that would affect the reaction rate and/or the amount of work being done.
Total time: 40 mins
Materials (estimated for a class of ~24 students):
8 20oz coke bottles (or any similar design)
1 box of non-latex gloves
1 package of rubber bands
1 box of small cups
1 box of Kim Wipes
60 Alka-Seltzer tablets
1 1/2 tablespoons of yeast
3 tablespoons of sugar
1 set of measuring spoons
1 heating pad
Ice
3 containers (to hold the ice)
Note: All of the materials for this experiment can be purchased at any
general store.
References:
Hypothesis (Will the Alka-Seltzer and water, water, or yeast and sugar reactants react most quickly?):
Label the three images as either doing the most work, less work, or no work.
Hypothesis (Will changes in concentration affect the reaction rate?):
Label the three concentrations as having either the fastest, medium, or slowest reaction rate.
Hypothesis (Predict the changes on the reaction rate caused by the variable temperature.):
Record how long it takes each glove to become entirely full at the different temperatures.
Cold (seconds) / Room Temperature (seconds) / Warm (seconds)Once again, label the images from the fastest to the slowest reaction rate.
What are some other variables that would affect the reaction rate and the amount of work being done?