Pre-Activity
Three students have conducted a controlled scientific experiment. They have
collected data and are wondering if their observations are qualitative or
quantitative.
Billy: “We measured temperature, the nitrogen concentration, the color of
the water, and the phosphorous concentration. I think we made quantitative
observations.”
Sarah: “ Yes, we measured temperature, the nitrogen concentration, the color
of the water and the phosphorous concentration. I think that we made both
qualitative and quantitative observations.”
Leo: “I think that you guys are both wrong. I think that our observations
were all qualitative.”
1. Which student do you think is right and explain why?
2. What is the difference between a qualitative observation and a
quantitative observation?
Investigating Water Quality
S.C Science Standard 8.1 Designing a controlled scientific investigation
In this lab students will learn about a controlled scientific investigation and
how this type of investigation can determine the water quality of a local
body of water. In addition the students will also learn about the differences
between qualitative and quantitative observations. Students will also review
important concepts such as independent and dependent variables, control
variables, and generating a hypothesis.
Introduction
On your lab table there are four plastic cups, which contain water from four
different sources of water. Today, you will be investigating which water
source is the most polluted by making qualitative and quantitative
observations.
Materials
-Plastic cups
-Test strips
-Water from 4 different sources
-Data Table
What is your hypothesis?
What are your independent/dependent variables?
Procedure:
1. Take one test strip and dip it into one of your plastic cups for 2
seconds. Shake once to remove the excess water
2. Allow colors to develop for 1 minute
3. After the color develops compare it to the color chart
4. Record the value you get from the color chart on your data table
5. Once you are done with the test strip throw it away in the trash
6. Repeat steps 1-5 for all of the plastic cups
Data Table
Test
Nitrate
Nitrite
Water Color
Water Clarity
Water Smell
Golf Course
Pond
Wall Pond
Miracle
Grow Water
Tap Water
Post Activity
Below are some data from my research. Indicate which is qualitative and
which is quantitative
Test
Moss 1
Moss 2
Moss 3
Moss 4
Percent
Nitrogen
2.8
5
4.0
2.4
Weight (g)
10.568
11.989
20.566
13.656
Moss Color
Very Green
Brownish
Green
Green with
brown tips
Dark Green
Moss
Description
Flat leaves
Closely
Closely
spaced leaves spaced
branches
Long thin
leaves