Fair Tests: Learn About Liquids
During this investigation, you will explore any question you
have about liquids. Using what you already know and have
observed related to density, viscosity and surface tension in
liquids, your team will make a prediction, consider the variables
and materials involved, and conduct your test.
Be sure to test only one variable and to determine how you will
control the other variables (keep them the same) during this
investigation. Plan how you will test your question and record
your results in an organized way. Decide what tools you need
to measure or collect data. Your conclusions should refer back
to the data you collected and discuss whether your prediction
was accurate. On a poster, your group will share any new
concepts you have learned from your results.
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Fair Tests: Learn About Liquids
Suggested Grade Span
3-5
Task
During this investigation, you will explore any question you have about liquids. Using what you
already know and have observed related to density, viscosity and surface tension in liquids,
your team will make a prediction, consider the variables and materials involved, and conduct
your test.
Be sure to test only one variable and to determine how you will control the other variables (keep
them the same) during this investigation. Plan how you will test your question and record your
results in an organized way. Decide what tools you need to measure or collect data. Your
conclusions should refer back to the data you collected and discuss whether your prediction
was accurate. On a poster, your group will share any new concepts you have learned from your
results.
Big Ideas and Unifying Concepts
Cause and effect
Models
Physical Science Concept
Properties of matter
Mathematics Concepts
Data collection, organization and analysis
Diagrams
Measurement
Time Required for the Task
Approximately two to three class sessions (after demonstrations).
Context
These fair-test investigations followed almost a week of explorations. Several teacher
demonstrations and guided small group activities introduced the concepts of density, surface
Fair Tests: Learn About Liquids
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tension and viscosity (or “laziness” as we called it) in liquids. We did about 2-3 activities for
each concept, including:
• A demonstration, placing raisins in clear soda. Students observed that at first, the raisins
sank; then bubbles began to attach to the bumpy surfaces, causing the raisins to rise; and
at the surface the bubbles burst, and raisins sank again. We discussed where the gases
came from and went to and also that the density of the raisins changed – with and without
bubbles attached – causing them to rise (when less dense than water) or sink (when more
dense than water).
• Observing how a cardboard boat floated and moved on water, before and after adding
dishwashing detergent (which changes the surface tension of the water). When we did it,
the boat suddenly moved across the water when soap was added.
• Observing paper clips staying on the surface of water when only a few were placed there
(observing surface tension and meniscuses – the curved surface of a column of liquid).
Students were then guided to suggest some testable questions to explore further. I suggested
that they use the phrase, “What would happen if ...” to begin to extend their thinking. Small
groups of students looked at the ideas each individual in the groups had generated and decided
on a question for the group as a whole to explore as a fair test.
What the Task Accomplishes
This investigation demonstrates a number of things. It enables students to practice designing
investigations, generating their own testable questions. It also demonstrates whether they
understand the idea of fair testing and controlling simple variables. Students also continue to
use and practice a number of science skills, such as observing, predicting, testing ideas, using
materials and tools, and drawing conclusions based on their observations and test results.
Students communicate findings and use their results to raise new questions to explore further.
The idea of “fair testing” and controlling variables is a difficult one. This task is part of ongoing
instruction in testing one variable at a time, measuring same amounts for each test, and relating
results back to the original question being tested. Additionally, I wanted to stress that while the
earlier observations that we have done were important, recording detailed observations and
using measuring devices to collect more precise data were the next steps in improving our
investigation process.
How Students Will Investigate
After the earlier class investigations already described, students were encouraged to explore
their own questions. The idea of fair testing was reviewed and led to students making decisions
and planning their investigations. I held conferences with groups of students at each step (after
choosing their question and making their prediction, after deciding on a process and materials,
etc.) to be sure that they were clear before going on.
Students worked in small groups and had access to different types of containers, household
liquids (water, syrup, food coloring, dish liquid, etc.) and various measuring devices, such as
stop watches. Students needed to decide what materials would be needed, how to measure or
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control amounts, and what process to use as they tested. They stated a testable question,
made a hypothesis/prediction based on their understanding, listed materials to be used,
described procedures to be followed, and collected data.
Interdisciplinary Links and Extensions
Science/Mathematics
Many students will raise new questions through these investigations. This can be an opportunity
to extend conceptual understanding of the properties of liquids and also introduce taking more
precise measurements as part of the data collection. By this age, students can begin to use
scales, stopwatches, and metric and standard measures for weight and volume, etc. with
confidence.
Small groups could explore further fair testing with density (the relationship between mass and
volume that causes something to float or sink), surface tension (the property of a liquid that
makes it behave as if its surface has an elastic skin) and viscosity (the measure of the
resistance of a liquid/fluid to flow: e.g., “Is warm syrup more lazy than cold syrup?”).
Note: In water, surface tension is very strong due to intermolecular hydrogen bonding and it is
responsible for bubbles, drops, meniscuses (the curved surface of a column of liquid) and
capillary action (rising of water in a tube, ability of a liquid to wet a surface or be absorbed by a
porous substance. Have students test the wetting properties of various liquids and substrates or
absorption rates of different materials.
Teaching Tips and Guiding Questions
If students are new to fair tests and controlling variables they will need assistance identifying
possible variables. Sharing possible testable questions as a whole class enables students to
hear a variety of ideas before deciding the variables they will test. Students may need some
help planning how to test their variable, deciding how and what to measure, and organizing
their data.
(Editor's Note: See the Exemplars Teacher’s Toolkit on this CD for some ideas for giving
students feedback to guide their fair tests.)
It’s helpful to provide students with models of different charts, tables and graphs (bar, scatter
plot, stem and leaf, etc.), appropriately labeled using science and mathematics vocabulary. As
students begin their testing, consider asking these questions to guide their thinking:
What is it you want to find out?
What is your prediction?
Does your prediction tell what you think will happen? (cause-effect)
Why do you think that will happen? What have you observed before that helped you make
this prediction?
• Is this is a fair test? What are you changing? What is staying the same?
• What materials will you need? What will you measure?
•
•
•
•
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•
•
•
•
•
•
•
•
What tools will you need?
Did you have to modify your experiment at any point?
What are your conclusions? How did you use your data to get your conclusions?
Did you explain your procedure clearly enough so that others can understand and perhaps
repeat what you did?
Can you support your conclusion using evidence from your results?
Have you used any science or mathematics terms to describe what you observed or
learned? (solid, liquid, gas, expand, variable, length, etc.)
What new ideas do you now have?
Do you have a new question to test?
Note: Remind students along the way that it is not important whether their prediction is correct,
but that they can use data and observations to justify or refute their prediction. This is what
scientists do!
Concepts to be Assessed
(Unifying concepts/big ideas and science concepts to be assessed using the Science
Exemplars Rubric under the criterion: Science Concepts and Related Content)
Physical Science – Properties of Matter: Students observe and compare physical properties of
matter. Students need to be able to use the terms or apply the concepts of surface tension,
density and viscosity appropriately and be able to describe cause-effect relationships with some
justification, using data and prior knowledge.
Scientific Method: Students observe and explain reactions when variables are controlled.
(cause and effect) Students see that how a model works after changes are made to it may
suggest how the real thing would work if the same thing were done to it and that choosing a
useful model (not too simple, not too complex) to explore concepts encourages insightful and
creative thinking in science, mathematics and engineering (models).
Mathematics: Students understand that representing and analyzing data appropriately,
identifying trends and patterns and using numerical data and precise measurements in
describing events, answering questions, providing evidence for explanations and challenging
misconceptions are important in scientific inquiry.
Skills to be Developed
(Science process skills to be assessed using the Science Exemplars Rubric under the criteria:
Scientific Procedures and Reasoning Strategies, and Scientific Communication Using Data)
Scientific Method: Using prior knowledge, using scientific reasoning, comparing, inferring,
predicting, observing, controlling variables, testing ideas, measuring, collecting and
representing data, drawing conclusions based upon results and communicating what was
learned.
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Other Science Standards and Concepts Addressed
Scientific Method: Students describe, predict, investigate and explain phenomena. Students
control variables.
Scientific Theory: Students look for evidence that explains why things happen and modify
explanations when new observations are made.
Physical Science – Properties of Matter: Students describe and sort objects and materials
according to observations of similarities and differences of physical properties.
Suggested Materials
Students used a simple planning guide as they worked to design their investigations. Groups
had access to different types of containers, household liquids (water, syrup, dish liquid, etc.),
various objects and measuring devices, such as stopwatches, and materials brought from
home. Planning investigations over several days allows time to gather materials needed for the
testing.
Students were provided with poster paper, markers, glue, etc., for drawing diagrams to explain
their experiments and for the final poster presentations. Some students also typed some of their
information, using school computers.
Possible Solutions
All information is presented on a poster to share with the class. This should include: a testable
question; a hypothesis showing a cause-effect relationship (“when I do this, this is what will
happen”); materials used; procedures followed, including variables to be controlled/variables
tested; data presented in an organized, clear way; and conclusions supported by data.
Drawings may also be included and should be labeled. Conclusions should refer back to data
collected and should discuss whether the prediction was accurate. A new question might be
raised.
Task-Specific Assessment Notes
Novice
These students complete the task. A testable question is stated, yet the hypothesis appears to
be more like random guessing than based on prior knowledge. Procedures are incomplete and
show little evidence of understanding fair testing. There is no reason given for having two jars in
the investigation and no mention that the drops of soap are to be the same each time. The data
collected are linked to conclusions made; however, there is no additional explanation as to why
three drops made the clip sink.
Apprentice
These students complete the task and provide a labeled drawing to explain what happened. A
testable question is stated, yet the hypothesis does not appear to be based on prior knowledge.
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Procedures are for the most part complete, although the students do not say how clips will be
put on the water (one at a time, etc.). There is limited evidence of understanding fair testing.
The data collected are linked to conclusions made, and there is an attempt to provide additional
explanation and interpretation. A logical new question, based on results, is raised – showing
evidence of scientific reasoning.
Practitioner
These students state a testable question linked to the concept of surface tension and make a
prediction based on prior knowledge and experience. Drawings are labeled and clearly show
each step. Procedures are complete and show evidence of understanding fair tests. Data are
collected and recorded. Conclusions are clear and refer to data and observations made.
Expert
(I have rated this Expert, mainly due to the precision in collecting, organizing, and displaying
data for the task.) The student states a testable question related to viscosity. The prediction
appears to be based on previous knowledge and experience. Procedures and explanations
show how each liquid will be tested. The student shows understanding of fair testing by using
the same amounts of liquids, timing each one going the same distance (to a finish line) and
recording results. Data are collected using a stopwatch. A table is used to organize and display
data. Labels make the table clear as to what was collected and represents accurately and
effectively what the students did during the investigation. Conclusions refer to data and
observations made. A new question is raised.
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Novice
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Novice
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Apprentice
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Apprentice
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Practitioner
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Practitioner
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Practitioner
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Practitioner
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Expert
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Expert
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Expert
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