What the teacher does :
Teacher will have materials needed for the activity: vial, sensor, electronic scale, baking soda.
Teacher will provide 1 virtual manipulative for equivalent fractions and 3 url’s for pH research.
Teacher will demonstrate the procedure once for the students to observe, and then they will follow the procedure to carry out the activity.
The teacher will measure out 4 ounces of water from the fish tank and pour it into the vial. The sensor is then used to measure the pH level of the water. The teacher will then measure .1 grams of baking soda on the electronic scale and place it in the vial of water. After mixing, the pH level will again be taken with a sensor to determine if the level is acceptable. An acceptable level for tilapia is 6.8-8.0 If it isn’t within this range, another .1 grams will be measured and again added to the vial of water. The procedure is repeated until the pH level is acceptable.
A record is kept each time .1 grams is added to the water in order to have an accurate amount of the chemical needed. Therefore, .1 would be multiplied by the number of times it was added to the vial of water.
In order to set up the proportion, the number of ounces in 1 gallon needs to be obtained. Measurements are written on the board indicating that 4 quarts is equal to one gallon. Therefore, to find the number of quarts in 10 gallons, multiply by 10.
4 x 10 = 40 quarts
If each quart has 32 ounces, then to find the number of ounces in 40 quarts, multiply 32 by 40:
32 x 40 = 1280 ounces
Before the proportion can be set up, the amount of water taken from the 10 gallon fish tank must be subtracted from the 1280 ounces to get an accurate answer. If there are 7 groups of students, 4 ounces must be multiplied by 7:
4 x 7 = 28 ounces of water taken out of the fish tank to check.
Now the proportion can be set up to find the amount of baking soda needed to change the pH level of the fish tank with approximately 1252 ounces of water in it.
# of Grams of baking soda = X grams___
4 ounces 1252 ounces
Since cross products are equal,
4 x X = # of grams x 1252
4X = # of g. x 1252
Divide by 4 on both sides of the equation to isolate the X amount.
(4 X)/4 = ( # of g. x 1252)/4
X = ( # of g. x 1252) divided by 4
X = # of g.of baking soda needed to change pH
The students would then be informed that once the answer is obtained, the amount of baking soda calculated would then be measured out and put into the 10 gallon tank of water. The pH level would then be checked by using the sensor. The pH level should be appropriate for the fish.
What the students do
Students will be grouped in 3’s and each group given a number. They will gather the materials needed for the activity:
One vial, sensor, electronic scale, baking soda.
Students will then proceed to do the same activity as demonstrated by the teacher.
They will: Measure out 4 ounces of fish tank water and check the pH level of the vial with the sensor. If the level is not between 6.8-8.0, the students will measure out .1 grams of baking soda on the electronic scale and place it in the vial of water. Mix and then measure the pH level of the water again and repeat procedure if the pH level is not acceptable. Once it is at the appropriate level, the amount of chemical needed is calculated by multiplying .1 g by the number of times it was added to the vial. The proportion can now be set up using the calculation of the number of ounces in 10 gallons, minus the number of ounces that were removed for testing by the groups.
# of Grams of baking soda = X grams___
4 ounces 1252 ounces
Since cross products are equal,
4 x X = # of grams x 1252
4X = # of g. x 1252
Divide by 4 on both sides of the equation to isolate the X amount.
4 X = # of g. x 1252
4 4
X = ( # of g. x 1252) divided by 4
X = # of g. of baking soda needed to change the pH
Once all groups have calculated their answers, a consensus will be taken to determine the amount of chemical that should be added to the fish tank water. Once added, the pH level will be determined with the sensor and the level should be appropriate.
Students will use the following lab report format for this activity:
Name __________________________________ Date ____________________
pH Level of Fish Tank Water Group # ______________
AIM: ____________________________________________________________
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MATERIALS:
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PROCEDURE/
EXPLANATION:
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PROPORTION: ___________________________________________
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EXPLANATION OF
CALCULATION:
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CONCLUSION:
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