Discovering Density Through "Lava Lamps"
Initial Publication Date: August 31, 2008
Summary
In this activity, students will mix several liquids and then add salt to the mix, simulating a "lava lamp".
Students will predict how the liquids will layer and then what effect salt will have on the mixture.
CollapseLearning Goals
Students will use science process skills such as: predicting, inferring, observing and questioning while following an experiment/method approach.
Vocabulary:
-Density
-Hypothesis
-Nucleation sites/point
Vocabulary:
-Density
-Hypothesis
-Nucleation sites/point
Context for Use
This activity can be done in the classroom without special lab equipment and can take from 30 minutes up to several days of class time if students are allowed to then perform inquiry on their own. Related activities are: "Dancing Raisins" and "Layering Liquids" etc.
Description and Teaching Materials
This activity should be in the middle of a unit on solids, liquids and gasses. They should already know what happens to oil and water when combined and the word density. Using the attached sheet, students will observe the layering of water, oil, and food coloring. They will then observe salt under a hand lens to see its crystalline shape. Using what they know about density and the dissolution of salt in water, they will predict what will happen when salt is added to this cup of liquids. Salt crystals have surfaces which have "nucleation sites" for bubbles or liquids to adhere to. The oil is attracted to the crystal and helps it "float" to the top and releases, letting the salt sink back to the bottom where it is more dense than the water.
The process is more important than the concept here, but reinforces density. In their guided inquiry, the students would try to put salt in other liquids to see if it does the same thing, or put other items in the liquids to see if they react as the same as the salt. Lava Lamp Inquiry Sheet (Microsoft Word 43kB Aug31 08)
The process is more important than the concept here, but reinforces density. In their guided inquiry, the students would try to put salt in other liquids to see if it does the same thing, or put other items in the liquids to see if they react as the same as the salt. Lava Lamp Inquiry Sheet (Microsoft Word 43kB Aug31 08)
Teaching Notes and Tips
The lesson is done in groups of 4, using cooperative group jobs. The activity could be done in pairs also.
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Assessment
The formal assessment would be the unit test provided by my district's curriculum on solids/liquids and gasses, but I would also do a performance assessment with each student individually or in pairs. While students take the test I would have pairs come up to a small table that has different solids, liquids and materials on it. They would have to demonstrate what they know about the materials using vocab words from the unit. I would use a checklist and students would probably have to demonstrate 80% of the vocab from the unit test. The attached inquiry sheet on "lava lamps" would be a regular assignment, not an assessment.
Standards
3.I.B.2 and 5.I.B.1
The student will participate in a scientific investigation using appropriate tools.
The student will perform a controlled experiment using a specific step-by-step procedure and present conclusions supported by the evidence.
4.II.A.3
The student will compare and contrast the mass, shape and volume of solids, liquids and gases
The student will participate in a scientific investigation using appropriate tools.
The student will perform a controlled experiment using a specific step-by-step procedure and present conclusions supported by the evidence.
4.II.A.3
The student will compare and contrast the mass, shape and volume of solids, liquids and gases