This is the new updated edition of the first book in the bestselling Uncovering Student Ideas in Science series. Like the first edition of volume 1, this book helps pinpoint what your students know (or think they know) so you can monitor their learning and adjust your teaching accordingly. Loaded with classroom-friendly features you can use immediately, the book includes 25 “probes”—brief, easily administered formative assessments designed to understand your students’ thinking about 60 core science concepts.

Access this probe as a Google form: English

Download this probe as an editable PDF: English

The purpose of this assessment probe is to elicit students’ ideas about thermal expansion. The probe is designed to find out whether students attribute expansion of the space between molecules to the rise of the liquid in a thermometer.

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kinetic molecular theory, thermal expansion, thermometer

Molly has the best answer: A thermometer is a closed system. It operates on the principle that the fluid inside it (usually alcohol or mercury) expands when heated and contracts when cooled. When the bulb is in contact with a warm object such as the hot water, energy from the hot water is transferred to the liquid inside the bulb. The molecules of the red liquid, in this case alcohol with a red dye added, gain energy and increase their motion as the faster-moving molecules bump up against and push the slowermoving molecules. This causes the molecules to move farther apart, and as a result, the alcohol inside the thermometer occupies more space as it expands. In order to occupy more space, the alcohol has to rise in the narrow tube. It is this increased motion and collisions of the molecules inside the very narrow tube that accounts for the rise of the alcohol.

Elementary Students

At the elementary school level, students use thermometers to measure the temperature of objects and materials. At this level they are developing the procedural skills of using a thermometer. They are not expected to know how a thermometer works.

Middle School Students

At the middle school level, students continue to use thermometers. They learn how a thermometer works and should be able to explain how it operates at a substance level—most substances expand or contract when they are heated or cooled. Some students can begin to use particle ideas to explain why a substance expands when heated and contracts when cooled and connect that to what happens inside a thermometer. At this stage they also recognize water as an anomaly to the idea that substances expand when heated and contract when cooled, noting that when water cools to form ice, it expands.

High School Students

At the high school level, students deepen their understanding of kinetic molecular theory and relate the thermometer phenomenon to particle ideas about thermal expansion. At this level, they are expected to be able to explain how a thermometer works based on the expansion or contraction of the liquid due to increasing or decreasing space between the molecules as a result of increased or decreased motion when energy is gained or lost by the molecules.

This probe can be demonstrated for students using a red alcohol thermometer or performed in small groups with appropriate safety precautions. The word volume is intentionally not used to describe the “liquid going up” in order to probe for younger students’ ideas related to the visible increase in the height of the liquid without having their lack of understanding of what volume is interfering with their ideas about the phenomenon. For middle school and high school students who understand the concept of volume, you can replace “His students disagreed about why the red liquid in the thermometer rose when the thermometer was placed in hot water” with “…why the volume of red liquid in the thermometer increased when the thermometer was placed in hot water.”

• Some students tend to regard liquids as continuous (nonparticulate) and static (Driver et al. 1994).
• In an Australian study of 25 children ages 8–11, children were asked how they thought a thermometer worked (Appleton 1985). About one-third of the children suggested the thermometer “was sensitive to heat,” or that it “was made to go to the right number.” Other suggestions involved pressure, pushing, or heat rising (Driver et al. 1994).

American Association for the Advancement of Science (AAAS). 1993. Benchmarks for science literacy. New York: Oxford University Press.

American Association for the Advancement of Science (AAAS). 2007. Atlas of science literacy. Vol. 2, “states of matter map,” 58–59. Washington, DC: AAAS.

Driver, R., A. Squires, P. Rushworth, and V. Wood- Robinson. 1994. Making sense of secondary science: Research into children’s ideas. London and New York: RoutledgeFalmer.

Keeley, P. 2005. Science curriculum topic study: Bridging the gap between standards and practice. Thousand Oaks, CA: Corwin Press.

National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academy Press.

Robertson, W. 2002. Energy, Stop Faking It! Finally Understanding Science So You Can Teach It. Arlington, VA: NSTA Press.

• Have students research how to make a thermometer and then have them build one. Students should demonstrate the use of their thermometers and explain how they work at a substance level and a particle level (if they are ready to use atomic/ molecular reasoning).
• Use the rising level of liquid in a thermometer as a plausible phenomenon to develop the idea that most substances expand when heated.
• Trace the transfer of thermal energy in a thermometer from the hot water to the glass to the alcohol. Have students draw a visual representation of the transfer of energy between molecules.
• Have students draw pictures to show what happens to the liquid in a thermometer at the particle level when the bulb comes in contact with hot material. Use the drawings (whiteboards work well for this) to discuss students’ ideas about conduction, the particle nature of matter, and kinetic molecular theory.
• Use the analogy of playing pool to illustrate what happens when molecules collide and transfer energy. When a pool cue ball hits a rack of pool balls, it transfers energy and the balls it hits spread out.
• Help the students who chose Jonathan’s response to understand how some words in science are used incorrectly. For example, the common phrase “heat rises” is incorrect. It is the warm air or water that rises, not the heat.
• Probe students’ reasoning further for each of the distracters chosen and challenge their ideas. For example, Greta’s idea can be challenged with conservation of matter reasoning, including the idea of a closed system in which no additional molecules can get into the thermometer.
• Relate expansion of the liquid in a thermometer to expansion of a metallic object. A metal ball and ring apparatus, available through most science supply stores, demonstrates how a metal expands when heated by showing how the ball passes through the ring before the ball is heated, but not after it is heated. Have students connect this phenomenon to what happens inside the thermometer.