In this lab, students
discover that many times there are qualitative and quantitative components
to science experiments. Qualitative data describes the situation
and reaction in descriptive terms. For example, qualitative involves
the senses including sight, taste, hearing, touch, and smell. This
would include color and shape. Quantitative includes those things
that can be measured. For example, describing something as a square
would be qualtitative, but measuring it and stating that it is 2 cm. by
2 cm. is quantitative.
In this experiment, students
will be collecting both quantitative and qualitative data. They will
be performing a chemical reaction caused by the mixing of vinegar and baking
soda. Baking soda plus vinegar reacts to form carbon dioxide (the
bubbles) and a liquid residue. The more baking soda students start
with, the more vinegar they will need to complete the reaction. Even if
more vinegar is added, a reaction will continue if there is more carbon
dioxide to be released from the baking soda (sodium bicarbonate).
(This experiment uses a lot of vinegar!)
When students record what happens
during this reaction, they should be aware that they must be able
to describe the reaction. They should be thinking: What do
I see, hear, or smell? This is qualitative science. However,
when they plot the data and interpret the result, it is quantitative science.
Students will make a bar graph of their results.
soda and vinegar in containers so that they can be easily distributed when
ready. If there are time constraints this lab can be done in
two periods. Students may do the hands-on portion one day and interpret
the results on a subsequent day.
- Discuss the difference
between qualitative and quantitative data. Tell students that today
they will be doing an experiment in which they need to record both qualitative
and quantitative information
- Pass out the lab
sheets. Review the lab procedure with the students. Remind
them that they are not only recording quantities of vinegar and baking
soda used (quantitative), but are also describing the reaction (qualitative).
As they are performing the lab they should be asking themselves: What do
I see, hear, or smell?
- When the students have
finished the lab, collect all the vinegar and baking soda. (If you
leave these out on the tables the students will keep experimenting until
they have to go home!) Explain how you would like them to do the
bar graph. Remind them that each bar should be a different color
to make it easier to read.
- Review the conclusion
questions with the students. Encourage the students to realize which
part of the experiment was quantitative and which part was qualitative.