Judy Lehmberg (FLC I) - Lee College

QUESTIONS:
1. Is solution A acid or base or neutral? Neutral, the pH is 7.
2. Is solution B acid or base or neutral? Acidic, the pH is 4.
3. Is solution C acid or base or neutral? Basic, the pH is 11.
BUFFERS A buffer is a chemical substance that can be added to water, and will make that solution resist a pH
change.
GO GET:
1. 25 ml of Sample X in a small beaker.
2. 25 ml of Sample Y in a small beaker.
3. A dropper - bottle of phenol red.
4. A dropper - bottle of acid.
NOW:
1. Put 5 drops of phenol red into each beaker. Phenol red is a pH color indicator. It turns yellow in acid, and
it turns red in base.
2. While counting the drops, add acid one drop at a time until each beaker turns yellow. Gently shake the
beakers after each drop in order to mix the acid into the test solution.
QUESTIONS:
1. Which solution contains a buffer, Sample X or Sample Y.
Sample X contains the buffer because it took more drops of acid to change its pH.
2. How many more drops of acid did it take to change the buffered solution yellow?
15 – 20 more drops
3. Why do you think that one of the brands of aspirin is called Bufferin?
Aspirin
Reflections
During the last year we have been exposed to critical thinking from a number of viewpoints; and not many of
those viewpoints have been those of a scientist. I have found that to be most helpful in discussing and
explaining what critical thinking is with my students, most of who are not, nor will ever be scientists. It has
given me a whole new set of words to use while explaining critical thinking. I will still use the scientific
method, but I will also use some of my new vocabulary to try to appeal to as many different students as
possible.
My participation in the FLC has also forced me to look at what I do everyday in my classroom. It has
reminded me that good teaching is an evolutionary process. I have gotten complacent. Now I have critically
looked at the labs I use, the tests I give, the homework, everything. I certainly will not change everything, but I
have already made several significant changes and I will do more next semester.
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