By surfers for surfers. Enjoy!

What Is True about the Particles in a Substance

Students should have the opportunity to apply scientific ideas on particle theory in other environments. Ask students to observe and explain changes in particle movement in scenarios such as wax or plastic melting, mothballs (naphthalene) disappearing into a closet, and the smell of perfume spreading through a room. In liquids, the particles are quite close to each other and move through the container with random movement. Particles move rapidly in all directions, but collide with each other more often than in gases due to shorter distances between particles. With an increase in temperature, particles move faster as they gain kinetic energy, resulting in increased collision rates and an increase in diffusion rate. Students at this level have been confronted with ideas about particles (including atoms, ions, and molecules) on several occasions, but many of them retain alternative or naïve views about the nature of particles, and these can inhibit their understanding. The goal is to adopt teaching strategies that encourage students` dissatisfaction with their existing ideas and promote plausible, coherent and useful scientific design in a variety of situations. Diffusion experiments can reinforce the idea of particle movement. These can also be used as points of interest. A number of questions raised in the “Conservation of Mass” development idea are relevant here, and weighing a vial containing a small amount of acetone before and after evaporation can be used to challenge students` ideas about the lightness of matter in the gaseous state and raise problems with static drawings of gas particles in texts. For more information, see: Preservation of the Mass. Since particles cannot be observed directly, a large part of the teaching is to look for obvious problems or gaps with the type of static images of particles given in previous years.

Encourage students to identify them and explain possible explanations. Some prompts: The atoms of the substance/element begin to vibrate faster. Kinetic energy increases. With a little encouragement, a class can usually discover through discussion that particles in gases must hit the bottom of the piston harder than the top and therefore be affected by gravity. This can be extended to explain why Earth`s atmosphere becomes thinner and eventually ends – the upward vertical motion of the particles stops. Student 1: “The particles begin to detach from each other due to the increase in temperature. When they have separated from each other, they transform from a crystalline form into a solution form. Many students who believe that matter is particles still retain some earlier views and consider that particles can change shape (solid to liquid), explode, burn, expand, change shape and color, or shrink.

Students visualize atoms, molecules, and ions as small spherical objects (perhaps because of the way the information was presented), which helps confuse the properties of particles with the macroscopic nature of the materials they are made of. Using activities such as POE (Predict-Observe-Explain) can help students reflect on their existing ideas and challenge them. The following activity will help students rethink their ideas about particle motion. The use of inaccurate or inaccurate language is problematic in textual documents, not just in illustrations. In particular, language that does not maintain a clear distinction between substances and atoms or molecules can cause students to attribute macroscopic properties or behaviors (such as hardness, color, or physical state) to individual atoms or molecules. For example, statements such as “perfume particles move further away when they turn into gas and diffuse into the air,” “Write a story from the perspective of a solid-phase particle when it melts and then evaporates,” and “draw what happens when the particles change state” (emphasis added) in an imprecise way that the particles themselves change state (melt, evaporate, etc.). On the next page, the idea is given as one of the four concepts of Dalton`s theory: “All matter is composed of tiny indivisible particles called atoms” (p. 158s). In Chapter 9, before learning more about thermal energy and temperature at the molecular level, students are reminded that “all matter is composed of molecules in constant motion” (p. 209s). In Chapter 6 and the beginning of Chapter 7, the term “particles” is used to refer to the molecules of a substance. In the student edition, for example, it says: Show students the conventional drawings of particles in solids, liquids, and gases and ask them if and how fast they think they are moving.

Idea e: There are differences in the arrangement and movement of atoms and molecules in solids, liquids and gases. In solids, particles (1) are densely packed, (2) are (often) arranged regularly, (3) vibrate in all directions, (4) attract and “stick” to each other. In liquids, particles (1) are densely packed, (2) are not arranged regularly, (3) can slide on top of each other, (4) attract each other and are vaguely connected to each other. In gases, particles (1) are distant from each other, (2) are randomly arranged, (3) evenly distributed in the spaces they occupy, (4) move in all directions, (5) are free from each other, except in collisions. There is a partial match with the content. The following illustration of idea e shows which parts of the idea are covered (in bold) and what alternative vocabulary, if any, is used (in parentheses): There are differences in the arrangement and movement of atoms and molecules in solids, liquids, and gases. In solids, particles (1) are densely packed, (2) are (often) arranged regularly, (3) vibrate in all directions, (4) attract and “stick” to each other. In liquids, particles (1) are densely packed, (2) are not arranged regularly, (3) can slide on top of each other, (4) attract each other and are vaguely connected to each other. In gases, particles (1) are distant from each other, (2) are randomly arranged, (3) evenly distributed in the spaces they occupy, (4) move in all directions, (5) are free from each other, except in collisions. Almost all parts of Idea e are addressed once in Chapter 6: Properties of Matter in the description of the phases of matter. However, some parts are not covered; These are heading 4 for solids, heading 4 for liquids, heading 2 for gases, the concept of “uniform distribution of particulate matter” in position 3 of gases and the concept of their free movement “except in the event of a collision” in position 5 of gases.

The different movements of particles of solids, liquids and gases are illustrated by an analogy with the movement of children in class and after. The different arrangement and movement of particles of solids and liquids are briefly associated with the particular shape and volume of solids and the absence of some form of liquids. The text states that gas particles do not adhere to each other and that “like particles in a solid or liquid, any gas particle is largely not affected by its neighbors” (p. 142s). In addition, the different attraction between diamond, graphite and soot particles is related to the fact that these materials have different properties (without specifying what the properties are). However, the idea that particles in all solids and liquids attract each other, or that particles in solids “stick” to each other, while particles in liquids are weakly related to each other, is not specifically addressed. Idea f: Changes in state – fusion, freezing, evaporation, condensation – can be explained by changes in the arrangement, interaction and movement of atoms and molecules. There is a partial match with the content. The following representation of idea b shows which parts of the idea are covered (in bold) and what alternative vocabulary, if any, is used (in parentheses): state changes – fusion, freezing, evaporation, condensation – can be explained by changes in the arrangement, interaction and movement of atoms and molecules. .