An Antarctic iceberg’s massive size is amazing, as is an Arctic glacier’s power to shape the landscape. Yet misconceptions about icebergs and glaciers exist among students of all ages (and adults). Many of these misconceptions deal with density and buoyancy; others concern the formation of glaciers and icebergs or their effects on earth’s land and water. Effective instruction begins by considering student misconceptions and planning activities accordingly.
In this article, we’ve highlighted some common misconceptions about icebergs and glaciers and the underlying concepts of density and buoyancy. Rather than provide an exhaustive list of all possible student ideas, we hope to give insight into ones that might be held by your elementary students. We’ve also provided tools for formative assessment and resources for teaching correct scientific concepts.
|Students may think…||Instead of thinking…|
|Icebergs are made of salt water.||Icebergs float in salt water, but they are formed from freshwater glacial ice.|
|Melting icebergs will cause sea level to rise.||Icebergs are already floating in the ocean, so melting will not raise sea level. Melting of land-based ice (such as glaciers) will raise sea level.|
|Students may think…||Instead of thinking…|
|Glaciers erode by pushing rocks.||Glaciers erode by plucking rocks and through abrasion. (For more information, see Glaciers: Earth’s Rivers of Ice.)|
A Note about Density and Buoyancy
Density and buoyancy are important concepts to consider when teaching about icebergs and glaciers. Answering common questions from students (such as why icebergs float or why glacial ice appears blue) requires some explanation of density and buoyancy.
Although the formal definitions and concepts are beyond grade-level expectations for elementary school, students can develop informal concepts of density and buoyancy as well as a basic understanding of what types of objects float or sink.
What are some of the common misconceptions about these concepts? Many students believe that heaviness is the most important factor in determining whether an object sinks or floats.
Students also may think that changing the shape of an object will change its mass or how the object floats. For example, many students will predict that a long piece of wood will float lower than a short piece of the same wood.
Researchers have also found that students investigating floating objects will focus on the object itself and ignore the water or other fluid in which it floats.
We have followed the model used by Page Keeley and coauthors in the four volumes of Uncovering Student Ideas in Science (© 2005-2009 by NSTA Press) and created a similar probe to elicit students’ ideas about the effect of melting icebergs on sea level.
This probe, modeled (with permission from NSTA Press) after those found in Uncovering Student Ideas in Science, Volumes 1, 2, 3, and 4, is designed to elicit student ideas about glacial erosion.
Density and Buoyancy
Volume 2 of the Uncovering Student Ideas in Science series contains several assessment probes that can help teachers identify misconceptions about density and buoyancy.
“Comparing Cubes” asks students to compare properties (mass, temperature, density, ability to float) of a large cube and a small cube made of the same material. It elicits student ideas about whether properties of matter change with increasing mass.
“Floating Logs” asks students to predict how a large log and a small one will float in water. It elicits student ideas about whether the size of an object affects its density.
“Floating High and Low” asks students to determine how to change how an object floats in water. It elicits student ideas about density and buoyancy.
“Solids and Holes” asks students to predict whether an object will float if holes are punched in it. It elicits student ideas about density.
Modeling icebergs and learning about the glacier-iceberg connection can help students understand that icebergs are made from fresh water. Models can also be useful in illustrating the effects of land- and sea-based ice on sea-level rise.
When Floating Ice Melts in the Sea (Grades 3-5)
Students use water and ice cubes to model what happens when floating ice melts. Students (and teachers) will observe that the melting of floating ice, such as icebergs and ice shelves, does not affect sea level. Challenge your students to modify the experiment to show what happens to land masses surrounded by water when ice melts.
When Land Ice Melts (Grades 3-5)
Students model the melting of land ice (glaciers and ice sheets) to discover that this type of melting does affect sea level. Challenge students to think about the block of wood. Does this effectively model what would happen to the land? What does the water represent? How could they modify the procedure to investigate what happens to another body of land in the same ocean?
Explaining Glaciers, Accurately (Grades 3-5)
This article from the National Science Teachers Association journal Science and Children describes two activities that help students develop correct understanding of how glaciers change the Earth’s surface by plucking and abrasion. Free for NSTA members and nonmembers.
Sink or Float? (Grades K-2)
Students make and test predictions about sinking and floating and classify objects according to whether they sink or float. Teachers can incorporate ice cubes into this lesson to focus on icebergs.
Sink It (Grades 3-5)
Students develop an experiment to test whether objects sink or float. Teachers can incorporate ice cubes into this lesson to focus on icebergs.
NATIONAL SCIENCE EDUCATION STANDARDS
Assessing and targeting student misconceptions about density, buoyancy, icebergs, and glaciers meets the Physical Science Content Standard and Earth and Space Science Content Standard for grades K-4 and 5-8 of the National Science Education Standards. The entire National Science Education Standards document can be read online or downloaded for free from the National Academies Press web site. Science Content Standards can be found in Chapter 6.
Copyright August 2009 – The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 0733024. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is licensed under an Attribution-ShareAlike 3.0 Unported Creative Commons license.