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Where did the Water Go? An Investigation in Scientific Methods
Grades: Grades 6-8
Author: Dr. Kathie Owens
Source: Inspired by an activity presented by Jon Valesek, Mississippi School for Mathematics and Science
As a result of the teacher-conducted discrepant event demonstration (described below), students will pose a problem. They will formulate their hypotheses, conduct experiments, and report their findings. Since it is unlikely that the students will be able to reproduce the outcome of the teachers' demonstration, it will be pointed out to them that very often scientific investigations do not lead to "answers".
What should students know as a result of this lesson?
- Students will realize that most scientific investigations proceed along organized approaches, frequently called scientific methods.
- Students will describe terms related to scientific methods: data, hypothesis, experiment, and findings.
What should the students be able to do as a result of this lesson?
- Students will pose a testable question, formulate a hypothesis, conduct an experiment, gather, process and analyze data, and report findings.
- For the teacher: three identical, opaque cups; small quantity of sodium polyacrylate (AKA WetLock); water
- For each group of 2-3 students: opaque cups identical to the teachers' cups; absorbent materials; water ./li>
The teacher will conduct the following demonstration:
- Out of sight of the students, put about a teaspoon of sodium polyacrylate in the bottom of one of three identical opaque cups.
- Tell students that you will be testing their powers of observations with an activity. The activity will be a variation of the "old shell game".
- Put the cups in plain sight of the students. Tell them that the cups are identical and "empty". Do not let the students look inside any of the cups.
- Pour about 1/4 cup of water in one of the cups without the sodium polyacrylate. While students are observing, switch the positions of the cups on the table. After several shifts, poll the students as to the location of the cup with the water in it.
- When students have guessed the water-cup, pour the water into the other cup without the sodium polyacrylate. While students are observing, switch the positions of the cups on the table. After several shifts, poll the students as to the location of the cup with the water in it.
- Pour the water into the cup with the sodium polyacrylate; switch cups around; poll the class. When you turn the cup that had both the water and the sodium polyacrylate (a polymer) upside down, no water will come out.
- Students will probably exclaim, "Where did the water go?" This question is the students' testable question for the next part of the lesson.
- Be sure to review what makes a test a "fair test" before proceeding.
Assessment: Make sure students are observing the demonstration. Monitor the students' responses throughout this part of the lesson. Make sure the students recognize that their response to the demonstration is their testable question.
Have available a variety of absorbent materials (cotton, paper towels, cloth pieces, etc.) and cups identical to those used by the teacher. Before any group experiments to answer its question, have the group write down its hypothesis and the series of steps it plans to follow. Students conduct their experiments, collect and organize their data, and formulate their conclusions.
Assessment: Be sure students are proceeding safely and following authentic scientific procedures.
Students report their findings and answer the posed question. After all reports have been shared with the class AND no group has been able to reproduce the outcome of the teacher's demonstration, the teacher discusses the reality that sometimes "nothing happens" as a result of scientific studies. "No findings" IS a finding! Sometimes scientists work for many years to show "proof" of their hypotheses, but are unable to "prove" what they seek. Emphasize the nature of scientific investigations. Remind students that they use scientific methods daily to solve everyday problems, like deciding what to wear to school.
Assessment: Have students summarize their understanding of the methods of science investigation and the nature of science as an endeavor. In their own words, students will describe terms related to scientific methods: data, hypothesis, experiment, and findings.
Hold a class discussion focused on the nature of science investigation by telling the stories of famous scientific discoveries. For examples: using analyses of mathematical calculations, Neptune was predicted before it was actually observed. Post-it notes are the by-products of a scientist's quest to make super-glue that did not measure up to standards. Well-known and long-held theories (like the geocentric solar system) are abandoned when contrary evidence is obtained. Students could research significant discoveries in science and summarize the methods used to bring about the findings.
Assessment: Ask students to discuss their perceptions of the nature of scientific investigative methods at the close of this discussion.
Misconceptions: Students may assume that the result of every science experiment results in "an answer".
Best Teaching Practices
- Inquiry Approaches
- Discrepant Event
Alignment with Standards
- MS-PS1-1 Develop models to describe the atomic compostion of simple molecules and extended structures.
- HS-PS1-2 Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table,and knowledge of the patterns of chemical properties.
Common Core Standards:
- RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts.
- RST.6-8.3 Follow preciesly a multistep procedure when carrying our experiments, taking measurements, or performing technical tasks.
- WHST.6-8.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.
- Content Standard A: 5-8 Science as Inquiry
- Grades 6-8 Scientific Inquiry Benchmark A
- Discrepant events are surprising or puzzling occurrences. They have unexpected outcomes and prompt students' questions, like, "How did that work?" When conducted well, they can be very motivating. So, we suggest that you practice this one first before conducting in front of students. For another example of a discrepant event – drop an orange into a vessel of water; observe that it floats. Peel the orange (now it weighs less) and watch it sink. Discrepant events do not appear to follow everyday rules for how things are "supposed" to behave.
- Science is characterized by exploration and explanation. Scientists "discover" that which can be directly observed and experienced. Science does not stop at exploration. Scientists look for patterns in their observations and propose explanations for their observations. Science is a way of knowing as well as the body of knowledge derived from those processes. Engaging students in the processes of building scientific knowledge by having them hypothesize, collect data, make observations, analyze their findings, and communicate their results helps them better understand the nature of science.
- Pick examples of everyday "problems" that students routinely address – for example, how to best manage their allowance with their desire to buy things – and have them apply the steps of scientific problem-solving to the situation.
- Remind students that scientists work for years on one "problem" – for example, finding a vaccine to prevent the spread of AIDS – with many apparent "no solutions".
Sodium polyacrylate is not considered a hazardous chemical, but the teacher should use care not to inhale this powder. For the students, there are no safety issues related to this lesson, however, the teacher will need to stress to the students that any absorbent materials used to test their hypotheses should be handled carefully and responsibly.
Throughout the lesson there are numerous connections to everyday life.
Pose another science problem or question to your students and ask them to design an experiment to address the problem. For example: which freezes faster - salt water or fresh water? Students will design and execute the steps needed to answer this question.
Grouping Suggestions: 2-3 per group.
Pacing/Suggested Time: Engagement: one day; Exploration: one day; Explanation: one day; Elaboration: one day
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