CTS Guide: Properties of Matter, pp 164-165- Section IV Research Summaries
Concept of Matter
Students in grades 4–8 may think that everything that exists, including forms of energy, is matter. Alternatively, they may accept solids as matter but not liquids and gases. Students at the end of elementary school and beginning of middle school may be at different points in their conceptualization of a “theory” of matter”. Although some third graders may start seeing weight as a fundamental property of all matter, many students in sixth and seventh grade still appear to think of weight simply as “felt weight”something whose weight they cannot feel is considered to have no weight at all. (AAAS 2009).
Many students age 15 and older still use sensory reasoning about matter, despite being well advanced in thinking logically in other areas, such as mathematics (Kind 2004).
Several studies have examined students’ ideas about gases. These studies show that students have difficulty accepting the idea that air and other gases have material character and that they have weight or mass. (Driver et al. 1994).
Lee et al. (1993) asked middle school students to consider which things that surround us in the world are considered matter. This turned out to be a difficult question for many students. Prior to being introduced to the word matter as a scientific term, students defined the term intuitively based on sensory perceptions, such as “matter is anything you can feel or you can see.” The textbook definition, “matter is anything that has weight (or mass) and takes up space,” was of little help for most students. Many thought that gases have no weight; others thought that light and heat take up space. Even after instruction, many students still had difficulties. For example, some students thought that “everything is matter, whatever exists,” including forms of energy. They also thought that forms of energy were not solids, liquids, or gases, but “different forms of matter.”
In a study of Israeli children ages 6–13, children were asked to decide whether a series of items were considered matter or nonmatter. The items were powders, rigid solids, nonrigid solids, liquids, biological materials, phenomena associated with matter such as fire and smell, gases, and nonmatter such as heat and shadow. Biological materials were regarded as matter less than 50% of the time. The study also showed that children’s ability to classify matter increases with age (Stavy 1991).
In a study conducted to find out the meaning students gave to the word matter, 20% of middle school–age students described it as something tangible, meaning it could be handled and took up space. By age 16, 66% of students described it this way (Bouma, Brandt, and Sutton 1990).
Intensive Properties of Boiling Point and Melting/Freezing Point
In a study examining Korean students’ conceptions of differing ice cube sizes, the students were asked, ‘‘What will the temperature of ice cubes of two differing sizes be when taken out of a freezer?’’ The percentage of students who thought that larger cubes produce colder temperatures was highest among students ages 4–9. Those students tended to think that temperature is related to material size. Around age 10, students in the study generally thought that size and temperature were unrelated; however, a significant percentage of 11-year- old students (55%) still related temperature to the size of the ice cube (Paik, Cho, and Go 2007).
An intuitive rule of “more A, more B,” may cause some students to reason that if you have more material, properties such as melting point or density increase. Students also may use this rule for reasoning about what happens to the temperature the longer a liquid boils. Based on the everyday experience that the temperature of an object rises when heated, students may reason that the longer you heat a substance after the onset of boiling, the higher the temperature will be. Students may use the intuitive rule “less A, less B” to reason what happens when you turn down the dial of a stove and the water boils gently. Using this rule, students may think that when the temperature dial is turned down, the boiling temperature decreases (Stavy and Tirosh 2000).
Many students think that the boiling point of water increases when the setting on a stove is “turned up.” Much of this confusion is related to a misconception that heat and temperature are the same thing. Students argue that if you increase the amount of heat, you will increase the boiling temperature (Driver et al. 1994).
Intensive Property of Density and Extensive Properties of Mass, Weight, and Volume
Until students understand that all matter has weight, even if they can’t feel it, they will struggle with the difference between extensive properties such as weight and volume and intensive properties such as density (Smith and Plumley 2016).
Some students age 15 and older still use sensory reasoning about matter, despite being able to think logically and use mathematics. They may recite a definition of density as mass over volume and perform density calculations yet hold a common belief that the more massive or heavy an object, the denser it is (Kind 2004).
Students will often mistake buoyancy-related phenomena for characteristics of density (Libarkin, Crockett, and Sadler 2003).
Young children’s ideas about weight are strongly associated with how heavy something feels (Snir, Smith, and Raz 2003).
Some students believe that when you change the shape of something, you change its mass (Stepans 2003). This belief can also interfere with their understanding of density.
Although some students ages 14–22 relate density to compactness of particles, incomplete explanations may result from their conceptions of mass and volume, which require understanding of the arrangement, concentration, and mass of particles. Many students have misconceptions about volume that present difficulties for understanding density. Students’ ways of looking at floating and sinking include the roles played by material, weight, shape, cavities, holes, air, and water. (Driver et al. 1994).
A study of 60 Australian 11-year-old students found that more than 80% had misconceptions about volume that led to difficulty in understanding density (Rowell, Dawson, and Lyndon 1990).
Biddulph and Osborne (1984) conducted a study during which some students ages 7–14 suggested that things float because they are light. When asked why objects float, the students offered different reasons for different objects. The same study asked students ages 8–12 how a longer candle would float compared with a shorter piece; many students thought the longer candle would sink or float lower.
A study by Smith, Carey, and Wiser (1984) found that students’ earliest ideas about density may be described by the phraseheavy for its size. However, students fail to bring together the two ideas of size and “felt weight” so that density and weight are not differentiated but rather are included in a general notion of “heaviness.”
Properties of Gases
Students may believe that matter does not include gases or that gases are weightless materials (AAAS 2009).
Gases pose special difficulties for children since the ones they commonly experience, like air and helium, are invisible. It is suggested that this invisibility prevents students from developing a scientific conception of a gas. Explicit instruction is needed for children to understand the properties of a gas, including properties like mass and weight. This is in contrast to solids and liquids where students tend to learn about them intuitively (Kind 2004).
Many researchers have noted that students do not initially seem to be aware that air and other gases are a type of “material” and thus have properties, such as weight or mass, like other materials (Driver et al. 1994).