Apologia General Science, Module 3, How to Analyze and Interpret Experiments

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This time we were learning about analyzing and interpreting the results of experiments.  We learned that in order to have the most accurate results, as many variables as possible must be eliminated.

With the first experiment, I had planned again to use teams of 2 since that seems to work really well.  Teams of 3 or more often mean that one is doing the experiment, and the other two are doing "Social" Studies, lol.  So with two kids only, there is no 3rd person to talk to.  =D
I learned that it is VERY IMPORTANT to check to see that you have ALL the supplies, even the most basic one that you keep in your home at all times.  I have been told that assuming will get you in trouble.
Well, I assumed.
We do experiments at my house, so I took it for granted I would have enough salt in my cabinet.  We barely had enough for one kid!  So Cousin A did it while the rest looked on...
and did Social Studies... of course.  =D

Experiment 3.1, A Floating Egg
The instructions said to see if an egg would float in a large glass of water, and of course it didn't.  Then she added 1 tsp. of salt at a time, and mixed.  After adding about 5 tsp. the egg did stand on its end, and after 7 tsp. it floated.  =)
We talked a little about density, and then talked more about variables.
In this experiment we eliminated as many variables as possible.  We used one glass and one egg.  Eggs do not vary greatly in size if from the same carton, but they could a little, I guess.
When removing the egg from the water each time to add more salt, we let as much water drip back in as possible to eliminate the water being reduced.
We also could have had 7 or 8 different glasses with increasing amounts of salt in each one, and different eggs, but again there could have been measurement error, or different sized eggs.  (Well, WE couldn't have used that many glasses -- I didn't have enough salt!)
These differences are so slight that they seem frivolous.  But it is important to always reduce or eliminate any variable that is not necessary for the experiment; the variables from which you learn nothing.
The salt was a variable, but it was intended to be part of the experiment.  It was the variable from which we wanted to learn something so it was necessary.

Next we did Exp. 3.2, Which Boat Will Move?
At the beginning of class, I had given all the kids a piece of gum, telling them we'd need a pinch or two later for an experiment.  I had some bins with books in them under my bed, so we used two of those, and JohnDavid poured in about an inch or so of water.  The kids cut out eight cardboard boats, then we added our "motors."
One "motor" was a balled-up piece of non-lotion kleenex, another was a pinch of gum, and the third was soap.  The experiment said use a piece of bar soap, but that didn't work for us.  Maybe because we use Dove soap?  But I knew dish detergent would work.  =)
We had four boats in each bin, so all the kids would not be crowded around one bin.  So what was our motor for the fourth boat?  Nothing.  This boat had nothing being done to it, so it was our control.  The control of an experiment is the variable or part of the experiment to which all others can be compared.
In other words, nothing was being done to this boat to cause it to do anything at all.  If the other boats did respond with a reaction, we knew it was because of what we did and not just a coincidence.


We discussed variables some more, and that we tried to make all the boats the same size and start them from the same starting point.  I tried having the kids place them in the water at the same time, but that caused just enough currents to make boats go everywhere!  Here they are finally still, and only move a little when the soap motor boat causes a slight current.
We also discussed how soap reduces the surface tension of water.
(Here is a practical application of soap reducing surface tension.)

We also did the pepper trick.  This is a video I found on youtube.  I didn't video ours.

We also learned about blind studies and double-blind studies.  It was a little difficult for the kids to grasp whether a blind or a double-blind study should be used.
At the beginning of class, I had all the kids to drink some pop (soda).  I had regular Coke and caffeine-free Coke and had previously poured 4 cups of each, labeling them A and B.  I was the only one who knew which drink was in A or B, but I told the kids not to let ME know which cup they got from the fridge.
So they didn't know what they drank, and I didn't know what they drank.
This is a double-blind study.
The purpose was to see whether caffeine makes teenagers in science class hyper.
Near the end of class, the kids all told whether they had drank from cup A or cup B, and I told them that cup A had the caffeine.
Then we discussed the variables:  Some people are more affected by caffeine than others.  Some may have had caffeine for lunch.  (Two of the students did.)  And at least one girl didn't even drink all of hers.
The results were inconclusive.  None of the students appeared any different to me than normal.  (hee hee, normal???)   Some are always more talkative (and busy!), and some aren't, including the two that had caffeine for lunch.

Since this experiment would involve my opinion, it needed to be double-blind.  This experiment was subjective to whether I thought someone was acting hyper or not, so I didn't need to know who had drank caffeine so I wouldn't possibly watch them more than the non-caffeine students.  Subjective experiments involve opinion, and always need to be double-blind.

An objective experiment is one where the results can be measured in numbers.
These may or may not need to be blind.
If there is an experiment to see what grades different types of students make, it needs to be blind so that the students will not know to whom they are being compared, and perhaps perform differently than usual.  But it does not need to be double-blind because the results (the grades) are not subjected to the observer's opinion.
If one is experimenting with the growth of plants, the results can be measured so this is also an objective experiment.  However the test doesn't need to be either blind or double-blind, because well, plants don't know what you are doing to them.  =D














We went over graphs just a little, and measured
the heights of teenage girls and boys.
We had boys and girls, and the ages vary, but this was not an experiment to discuss variables, but just to review graphing.  They had fun with it.
I didn't know my ds14 was 5'10" though!  =)

sMiLeS,

Apologia General Science, Module 2, Scientific Inquiry

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We learned that sometimes an experiment seems to "prove" something, but actually has faulty results.
I put 'prove' in quotes because we also learned that science cannot prove anything!

In Experiment 1.1, How Does Weight Affect the Speed at Which an Object Falls? the kids dropped several items to see which would hit the ground first.  I divided them in teams of two.  The experiment called for a sheet of paper, a sheet of cardstock, a sheet of cardboard, and a heavy book.  All needed to be about the same length and width.  Well, I wasn't about to let the kids drop books, so we used 4 small removable shelves that I had.  And we dropped them on the carpet, of course.
This experiment seemed to indicate that heavy objects fall faster than lighter objects, but that was shown to be incorrect with our next experiment.

Experiment 2.2 called for the same items and added in a small rock and a paperclip.  This time, however, the kids were to ball up the sheet of paper.  This experiment showed that only because of wind resistance did the sheet of paper fall slower before.  Now it would hit the ground at about the same time as the other objects.
So we learned that in the absence of air, all objects fall at the same rate.  Well, there is air all around us, so you need to look at the object being dropped and consider the wind resistance it will encounter.

So, this second experiment was a counter-example.  A counter-example contradicts a scientific conclusion.  This is very important.  Scientists are discovering new information all the time - and it only takes one counter-example to contradict a conclusion that may have been accepted for many years!

We did not do Experiment 2.3, The Broken Flashlight, simply because I didn't have enough time to "fix" everyone's flashlights.

We did do D & T (you aren't supposed to know what the letters mean until afterwards).
In D & T, the kids had 22 words written on cards that made up one long sentence.  I printed them on cardstock in a light color so they would not show through when turned over.  I had 4 teams, so I did 4 different colors to keep the sets of words separated (mainly for me while I was getting them together!)

The kids turned over 5 words and wrote them down on this worksheet, then made a hypothesis as to what they thought the sentence was about.  Each student had their own worksheet.  I told them not to worry over whether they are right or wrong;  a hypothesis is what you think is the answer.  They turned over 5 more cards, and naturally, their hypotheses changed.  This is the way of experiments.  As you gain more knowledge, your hypothesis will change.  They continued turning over 5 cards at a time until all were turned over.  All 4 teams had different hypotheses, and some were very funny!  This sentence had several phrases and several adjectives, so it could go in many directions.
It was so fun, but I don't want to give it away.  You'll just have to try it yourself.  =)

We also did the Scientific Method in Action.  These were two real examples so the kids got to see how science really works, not just playing around with a sentence.  First we read a little about beriberi and about a scientist who had a hypothesis.  The kids answered questions about what was the hypothesis, how was it tested, should the hypothesis be supported or rejected based on the results, and should there be a new hypothesis, etc.  Then we read a little about the discovery of penicillin and answered similar questions.
Here is also Scientific Method Explained.




These experiments are simple, but are meant to show that a counter-example can refute a hypothesis, a hypothesis may then need to be changed, and that as you get more information, your hypothesis will change or be confirmed.

sMiLeS,