Learning Progression Developed to Support Students in Building a Particle Model of Matter

Abstract

The particle nature of matter is a core idea of science that serves as the building block for understanding states of matter phase changes and properties of substances. Science educators have started to explore learning progressions as a means for understanding how students develop their knowledge of complex science content over time. The development and application of progress variables is one method that has been suggested as a means for tracking students’ knowledge. The How can I smell things from a distance? sixth grade (ages 11–12) chemistry unit takes the approach of building students’ ideas through students’ development of particle model of matter. The empirically validated particle model of matter progress variable was used to track 122 students’ development toward a particle model of matter. Results show that well-aligned curriculum and assessment can help students to develop a particle model of matter.

Appendix

Lesson Descriptions and Learning Performances for the How can I smell things from a distance? Unit

	Lesson no.	Description	Learning performance
Learning set 1	1	Students smell odors coming from two jars, recognizing that the jar must be open in order to smell an object. During this investigation, students draw pictures and write descriptions that represent their understanding. Next, the teacher facilitates a discussion to help students think about (a) how odors travel and (b) how scientific models help them to understand and explain this phenomenon	Students construct initial models to help them explain how odors travel across a room Students describe one purpose of a scientific model
	2	Students measure the mass and volume of different substances, including an inflated/deflated ball to understand that odors and air have mass and occupy space (have volume) and conclude that anything with mass and volume can be called “matter”	Students describe air as occupying space (having volume) and having mass Students identify the relationship between the amount of a substance and the measured mass of that substance Students characterize things as matter (or not matter) based on whether they have mass and volume
	3	Students classify materials as solid, liquid, or gas. Students learn that matter can go through phase changes by observing the melting and cooling of menthol. As an optional activity, students can also observe the phase changes of water	Students identify and describe materials in three states of matter, using scientific terminology (solid, liquid, gas) Students describe and compare the characteristics of solids, liquids, and gases Students describe typical changes of states that occur when substances are heated or cooled Students provide examples of materials changing states
	4	Students investigate the ability of air to be added and removed, expanded and compressed in closed systems, using their own models to explain them. Through the critique of their models, students begin to understand that the building blocks of matter are particles. Empty space between the particles explains addition, subtraction, compression, and expansion	Students construct and revise models to explain and account for all of the following phenomena: subtraction, addition, compression, and expansion of gas in a closed container
	5	Students develop an understanding that matter, in the gaseous state, contains particles that constantly move in linear motion by observing indicator paper changing color without being dipped in two different liquids. Students also view a simulation of odor traveling in a room with air. By the end of this lesson, the class develops a consensus model for the particle model of matter	Students construct models of the particle nature of gases Students use their models to explain why indicator paper changes color and how smell travels Students describe evaporation as particles of liquid changing phases to particles of gas without boiling
Learning set 2	6	Students observe and record the emission spectra of different gases. Through discussion of their data and modeling of different gases, students come to the idea that different materials have different properties; thus, we can distinguish among materials based on their properties	Students compare one substance to another, based on their properties
	7	Students are introduced to the elements of the periodic table and the physical properties of elements, by observing and investigating different elements. Students use their results to explain that the elements have different properties because they are made up of different types of atoms. Students are also introduced to fundamental concept of the atom – as a basic particle of all elements	Students compare several elements to one another, based on observable properties and uses Students define what an element is using the concept of atoms (and not particles)
	8	Students create molecular models of oxygen, carbon dioxide, nitrogen, and water using gumdrops, Styrofoam balls, or other molecular modeling kits to represent atoms and molecules. The molecular models are then placed in a clear bag to represent air as a mixture of gases. The teacher facilitates discussions to help students understand these models and to introduce molecules as being composed of more than one atom that “stick” together and that different molecules make up different substances	Students use physical representations to explain the relationship between molecules and atoms Students identify a sample item as either a substance or a mixture on a molecular level
	9	Students rotate through stations smelling different substances. Each station will include a 2-D image of the molecule. Students recognize the fact that the same atoms (C, H, O) can be in different arrangements and that these different arrangements make a new substance with new properties (in this lesson, a different odor)	Students explain that different smells are caused by different arrangements of atoms in a molecule, using molecular models
	10	Students observe the time it takes ammonia vapors at different temperatures to reach indicator paper Students revisit the virtual simulation of air and odors in a room, manipulating temperature to show the difference in molecular movement at higher and lower temperatures	Students predict how molecules move at different temperatures Students describe what happens to the molecules in a gas when it is cooled and heated Students construct models to demonstrate that molecules have different speeds at different temperatures Students explain why an odor moves faster at higher temperatures
	11	Students observe the cooling and heating of a balloon placed in and removed from a dry ice bath. Students use the particle model to explain their observations. Finally, a mechanical model is used to demonstrate the relationship between temperature and volume in the heating and cooling of gases	Students describe what happens to the molecules in a gas when it is cooled and re-heated Students explain the relationship between temperature and volume of gases
	12	Students observe the heating and cooling of bromine and create models of bromine in both the gas and liquid phase to help understand the process of evaporation. Then, students observe the evaporation of alcohol and water from two different surfaces to understand that different substances, which are composed of different molecules, have different evaporation rates. Third, a teacher demonstration of water boiling is used to explain the process of boiling and what happens as a liquid undergoes a phase change to gas. Students model the process of boiling to develop understanding of this process. Finally, students observe the process of condensation, through water condensing and evaporating in a bottle and the condensation of water on the outside of a plastic cup filled with ice water	Students explain phase changes from gases to liquids and liquids to gases at the molecular level
	13	Students observe the expansion of water when it is heated and create physical models to explain their observations. Students then use their models to predict what happens when dye is added to hot and cold water. Students discuss whether their predictions match their observations and revise their models accordingly	Students describe the difference between liquids at different temperatures, including the fact that liquids expand upon heating Students explain the difference between liquids at different temperatures using a particle model
	14	Students observe the phase change from a solid to a liquid by observing ice melting and through a teacher demonstration of melting an unscented, paraffin wax candle, creating models of solid and liquid water (or wax). Students observe sublimation using dry ice. Teacher reviews the menthol experiment (Lesson 3) and students create models of the molecules in the solid, liquid, and gaseous states	Students explain phase change from a solid to a liquid and from solid to a gas (sublimation), using the particle model Students explain different states of same substance, including in their explanations that the particles are the same but behave differently
	15	Students revisit the models they created during Lessons 1 and 5 and create models of smell. The class reviews what they learn and develop a class consensus particle model. Then, students use their consensus model to address a real-world problem	Students evaluate models (compare and critique their models of odor) Students explain a related phenomenon, which is presented in a format of a short newspaper article, using the particle model Students create a poster/brochure suggesting a solution to a real-world problem