6.2.1.2 Physical Change
Identify evidence of physical changes, including changing phase or shape, and dissolving in other materials.
Describe how mass is conserved during a physical change in a closed system.
For example: The mass of an ice cube does not change when it melts.
Use the relationship between heat and the motion and arrangement of particles in solids, liquids and gases to explain melting, freezing, condensation and evaporation.
Overview
"No matter how parts of an object are assembled, the weight of the whole object made is always the same as the sum of the parts, and when a thing is broken into parts, the parts have the same total weight as the original thing." (4D/2 in the 3-5 band) Benchmarks
Big Idea:
State of Matter: Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated. (4D/M3ab) In solids, the atoms or molecules are closely locked in position and can only vibrate. In liquids, they have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. 4D/M3cd
Changes of state: Almost all matter can exist in more than one state and temperature is most often what causes it to change from one state to another.
Conservation of Mass: No matter how substances within a closed system interact with one another, or how they combine or break apart, the total mass of the system remains the same. (4D/M7a*)
Heat Energy: Heat increases the motion of particles in matter which in turn may cause changes in properties and state.
MN Standard Benchmarks :
6.2.1.2.1: Identify evidence of physical changes, including changing phase or shape, and dissolving in other materials.
6.2.1.2.2: Describe how mass is conserved during a physical change in a closed system.
6.2.1.2.3: Use the relationship between heat and motion and arrangement of particles in solids, liquids, and gases to explain melting, freezing, condensation, and evaporation.
THE ESSENTIALS:
This website contains a collection of animated cartoons that offer a brief introduction to changes in the state of matter. They can be used to introduce particle theory during state changes. In order to view the cartoons, you must read the directions on the page and select the appropriate links.
- NSES Standards:
Materials can exist in different states-solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling. (K-4 strand, p. 127)
Solids, liquids, and gases differ in the distances and angles between molecules or atoms and therefore the energy that binds them together. In solids the structure is nearly rigid; in liquids molecules or atoms move around each other but do not move apart; and in gases molecules or atoms move almost independently of each other and are mostly far apart. (9-12 strand, p.179)NSES
AAAS Atlas:
Volume 1, Structure of Matter: Atoms and Molecules, Conservation of Matter, and States of Matter p. 54-59
- Benchmarks of Science Literacy
Benchmarks for Science Literacy
By the end of the 8th grade, students should know that
All matter is made up of atoms, which are far too small to see directly through a microscope. 4D/M1a
The atoms of any element are like other atoms of the same element, but are different from the atoms of other elements. 4D/M1b*
Atoms may link together in well-defined molecules, or may be packed together in crystal patterns. Different arrangements of atoms into groups compose all substances and determine the characteristic properties of substances. 4D/M1cd*
Equal volumes of different materials usually have different masses. 4D/M2*
Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated. 4D/M3ab
In solids, the atoms or molecules are closely locked in position and can only vibrate. In liquids, they have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. 4D/M3cd
No matter how substances within a closed system interact with one another, or how they combine or break apart, the total mass of the system remains the same. 4D/M7a*
The idea of atoms explains the conservation of matter: If the number of atoms stays the same no matter how the same atoms are rearranged, then their total mass stays the same. 4D/M7b
Most substances can exist as a solid, liquid, or gas depending on temperature. 4D/M8** (SFAA)
- Common Core Standards (i.e. connections with Math, Social Studies or Language Arts Standards):
RST.6-8.4. Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 6-8 texts and topics.
Misconceptions
- Students cannot understand conservation of matter and weight if they do not understand what matter is, or accept weight as an intrinsic property of matter, or distinguish between weight and density (Lee et al., 1993;Stavy, 1990).
- Many students can understand qualitatively that matter is conserved in transforming from solid to liquid. They also start to understand that matter is quantitatively conserved in transforming from solid to liquid and qualitatively in transforming from solid or liquid to gas-if the gas is visible (Stavy, 1990).
- For chemical reactions, especially those that evolve or absorb gas, weight conservation is more difficult for students to grasp (Stavy, 1990). (Atlas, p. 56)
- Students of all ages show a wide range of beliefs about the nature and behavior of particles. They lack an appreciation of the very small size of particles; attribute macroscopic properties to particles; believe there must be something in the space between particles; have difficulty in appreciating the intrinsic motion of particles in solids, liquids and gases; and have problems in conceptualizing forces between particles (Children's Learning in Science, 1987).
- Despite these difficulties, there is some evidence that carefully designed instruction carried out over a long period of time may help middle-school students develop correct ideas about particles (Lee et al., 1993). (Atlas, Vol. 1, p. 54)
- Elementary and middle-school students may think everything that exists is matter, including heat, light, and electricity (Stavy, 1991; Lee et al., 1993).
- Alternatively, they may believe that matter does not include liquids and gases or that they are weightless materials (Stavy, 1991; Mas, Perez, & Harris, 1987).
- With specially designed instruction, some middle-school students can learn the scientific notion of matter (Lee et al., 1993). (Atlas, Vol. 1 p. 54)
- Middle-school and high-school students are deeply committed to a theory of continuous matter (Nussbaum, 1985b).
- Although some students may think that substances can be divided up into small particles, they do not recognize the particles as building blocks, but as formed of basically continuous substances under certain conditions (Pfundt, 1981). (Atlas, Vol. 1, p. 54)
- Students at the end of elementary school and beginning of middle school may be athdifferent points in their conceptualization of a "theory" of matter (Carey, 1991; Smith et al., 1985; Smith, Snir, & Grosslight, 1987). M
- Many students in 6th and 7th grade still appear to think of weight simply as "felt weight"-something whose weight they can't feel is considered to have no weight at all. Accordingly, some students believe that if one keeps dividing a piece of Styrofoam, one would soon obtain a piece that weighed nothing (Carey, 1991). Atlas, Vol. 1, p. 54)
- The concept of weight as a pulling-down force and the concept of mass develop slowly. The word mass is often associated by students with the phonetically similar word massive, and thus students often think the mass changes if there is a change in size or volume. Students often compare mass by bulk appearance.
Driver, Rosalind, Squires, Ann, Rushworth, Peter, & Wood-Robinson, Valarie. (2003). Making sense of secondary science. New York, New York: Routeledge.
Vignette
Miss A opens her class with a discussion about dissolving. She asks students what kinds of solutions they make at home by dissolving a solid into a liquid and what kinds they have made in school in the past. After a bit of conversation, she pulls out a container of Kool Aid and asks the students if they'd like some. They all are surprisingly thirsty.
She stirs the kool aid into the pitcher of water and the students watch as the powder disappears. She asks the students to discuss what changes they can observe in the liquid. What changes do they know have occurred even though they cannot see it. After giving the students a few minutes to discuss at their table, agree on two changes: color and taste.
They then have a discussion around the dissolving and she poses the question: even though the kool aid powder dissolved, is it still in there. The students believe it is, and that their evidence is the change in taste, but they can't agree on how much is still in there. Some believe that all the powder still exists in the liquid, others believe some of the solid is gone.
Miss A. then asks the students to if they can find out if all, some or none of the powder still exists in the solution. She then makes available a number of measuring materials, water, mixing containers and Kool Aide powder. The students are asked to come up with a plan for figuring it out. As the student groups devise their plans, they present their ideas to Miss A. for approval and procede. With some facilitation, guidance, and observing each other, most of the groups come up with measuring the mass of the water, and the mass of the kool aid. They then mix the two and measure the mass of the drink. The students discover there is no mass lost.
The class then sits down to enjoy their beverages and Miss A. walks around the room putting ice cubes in each cup of warm Kool Aid. As she does she asks the students, "Ice is just frozen water right? And water changes from a liquid to a solid when it freezes, correct? Are there any questions we could ask about that change?"
A student shouts out, "Does the mass of the water in the ice cube tray change when the water freezes?!"
Tomorrow's lesson has already begun...
Miss A opens her unit regarding physical changes by distributing common household supplies to each lab station. Station one contains ingredients for ooblick, station two is provided with a styrofoam cup filled with ice cubes, road salt, a thermometer, and a plastic bag, station three is handed a Jenga game, and station four is given supplies for making Koolaid. Each group is also provided with a set of lab instructions and reflection questions. Each set of instructions requires the group to perform an activity that demonstrates a physical change. Guiding questions follow the activity and allow students to realize the characteristics of a physical change.
Miss A circulates around the room and supports learning groups with their tasks. While one group is noticing properties of ingredients before and while making KoolAid and Ooblick, another group of building and manipulating a Jenga tower. Yet another group is analyzing the freezing/melting point of water before and after salt is added. The students are curious about the supplies and the new science topic, and the materials add excitement and motivation to the unit.
It does not take long for the students to practice their investigations and begin to notice the physical attributes that change in each challenge. Soon attention begins to wander from the assigned lab to that of the neighboring labs. Miss A takes full advantage of the opportunity by allowing each group to present their activity and learnings. Groups are responsible for sharing the list of original materials, as well as two physical properties of each material. Then the groups describe the process of the lab, and summarize by sharing the properties of the material after the procedure was completed. Miss A praises the groups for their focused attention and enthusiasm and summarizes the lab's purpose by defining "physical change."
Resources
Instructional suggestions:
Provide students with opportunities to create, observe, compare, and reflect on both physical and chemical changes.
Utilize science journals as a resource for recording facts and creating graphic organizers comparing physical and chemical changes. Consider using Science-Class.net Graphic Organizersas a source for graphic organizers in science notebooks.
Combine science literature with hands-on measurement activities to demonstrate how mass is conserved in a physical change taking place in a closed system.
Selected activities:
6.2.1.2.1: Gobstopper Lab:
"This activity is designed to look at properties of objects and materials and changes of properties of matter. The basic process skills of observing, inferring, and communicating are developed along with concepts involved with matter and its changes."
Jorgenson, Olaf, Cleveland, Jackie, & Vanosdall, Rick. (2004). Doing good science in middle school: a practical guide to inquiry-based instruction. Arlington, VA: NSTA Press.
6.2.1.2.1: Physical and Chemical Change Sorting Activity
In this card sorting activity, students look at a variety of pictures depicting both physical and chemical changes. Students are challenged to sort the cards based on the type of change, and provide a brief explanation as to why they chose to sort the cards as they did. Ultimately, the class works as a whole to determine the factors that must be evident in order for a change to be a physical change and a chemical change. This activity should be used with advanced students, who have mastered the concept of physical changes and are prepared to identify a non-example of a physical change.
6.1.2.2: Conservation of Mass in a Closed System.pdf
In this lab, students are provided with an explanation of "conservation of mass in a closed system." Students are provided with a set of materials, and their task is to design an experiment that demonstrates the conservation of mass in a closed system. After designing the experiment, they conduct it and graph the mass of the materials before, during, and after the experiment is completed. This lab would be best used to reinforce the concepts associated with the benchmark.
6.2.1.2.3: NASA: Can Sea Water Freeze?
This lesson looks at the freezing point of water, and demonstrates how the freezing point of water is lowered when salt is added to the water. The lab reinforces the particle theory of matter as it relates to physical changes and will help students to understand why salt is spread on the road in the winter. It might be used later in instruction to help students explore concepts as they relate to life outside of school.
This research-based document, Ideas for Teaching Science, provides hands-on labs and literacy activities for both elementary and middle level students who are learning about physical properties and physical changes in matter. The activities range from creating a concept map depicting state changes to making butter to discuss the composition and properties of mixtures.
Additional resources or links
This interactive simulation allows students to select the state of matter they wish to study. The simulation demonstrates how the state of matter is created from the liquid state (heat is added or subtracted) and offers a "microscope's view" of the particle behavior associated with the particular state.
In this "Dirt Meister" lab by Scholastic, students utilize the scientific method to create a "mystery substance" with unique physical properties. Then they "force" physical changes to occur to the substance. The lab provides a simple, concrete way to explain physical changes.
6.2.1.2.1 and 6.2.1.2.3: Exploratorium
"The atomic theory of matter tells us that a gas is made up of tiny particles called atoms (or molecules, which are combinations of atoms), which are constantly in motion, smashing into each other and the walls of their container, if there is one. Here is a highly visual model of this idea."
Vocabulary/Glossary:
Conservation of Mass--The mass of a closed system will remain constant over time.
Solid, Liquid, Gas--The three common forms of matter
Matter--Anything that has mass and takes up space
Physical Change--When substances go through at change that does not change their chemical make up.
Closed System - a system "isolated from its surrounding environment." No energy or matter into or out of the system.
Phase - The state of matter that an object exhibits. Ex: Solid, liquid, gas, or plasma.
Melting Point- The temperature at which a solid becomes a liquid.
Freezing Point- The temperature at which a liquid becomes a solid.
Condensation - The state change of a gas to a liquid
Evaporation - The state change of a liquid to a gas.
6.2.1.2.1 and 6.2.1.2.3:
PhEt States of Matter Simulation
In this online simulation, students add or subtract heat to a substance and observe the particle behavior of the matter.
6.2.1.2.1 and 6.2.1.2.3: These "bite size" video clips demonstrate physical changes in matter. Short literacy activities are accompanied by online games and demonstrations. These video clips can be used to explain, reinforce, or review physical changes in matter.
Art connection: For Benchmark 6.2.1.2.3 take time to examine websites with particle models and simulations that illustrate particle motion. Have students design posters to explain these changes in motion caused by heat. Discuss with students how to show motion of the particles on a non-moving platform.
Assessment
Students:
Summative: (Knowledge, Application)
1. Popcorn kernels contain a solid material called starch and a small amount of water at room temperature. When the temperature of the kernels of popcorn increases, they explode or pop. Which change in the state of the water takes place inside the kernel, causing volume to increase?
A. solid to gas B. liquid to gas [correct answer] C. solid to liquid D. liquid to solid
Formative:
List three examples of physical changes and three non-examples of physical changes
Teachers:
Questions could be used as self-reflection or in professional development sessions.
Why is it important for students to recognize that not all physical changes are reversible?
Most students will likely not be engaged in a physics course again until 9th grade. However, it is important that they understand and can identify physical changes before engaging in Life and Earth Science Courses. What strategies will you use to encourage students to apply physics knowledge to the Life and Earth Sciences?
What do students need to know about matter before they can begin learning about physical changes?
Administrators:
If observing a lesson on this standard what might they expect to see.
Students should be engaged in a lab that demonstrates physical changes. Students should be articulating their observations of the physical properties and identifying the variable that caused the physical change to occur.
Differentiation
Struggling and At-Risk:
Utilize hands-on labs that focus on one objective at a time. Research activities and labs that match the interests of the students in the room. Provide guided questions to direct student thinking throughout the labs.
Post the vocabulary terms related to physical properties and physical changes with pictures depicting each term. Point to the term and the photo as it is used in lessons.
While developing Matter concepts with ELL students make sure to
- Illustrate and diagram concepts with vocabulary on the board during discussion
- Give step-by-step directions for labs
- Prepare word walls or glossary sheets with illustrated vocabulary for students to easily access
- Summarize discussion and learning more frequently
- In setting up groups, pair non-native with native speakers.
- Make connections to the students' out of school experiences
- Vary instructional delivery to include picture books, video, etc.
G/T:
Have students research and diagram a cross section of a popcorn kernel to reveal the water trapped inside. Can you elaborate on the reason that popcorn pops? What happens to the starch in the popcorn kernel? This is something that students will probably ask about, too. What kind of change is it and why? What about the kernels that do not pop-ask students to think of the causes for this. What about the kernels that burnt or get scorched?
Science Scope, October 2009 Enhancing Student Understanding of Physical and Chemical Changes.pdf
Research physical changes that take place in nature. Identify examples from a variety of countries.
Have students make a foldable that identifies the name, picture, and example of each type of physical property.
Parents/Admin
Benchmark 6.2.1.2.1 can be reinforced in the kitchen at home as families bake and cook meals together. Parents should be asking their students to describe the changes that to materials as they are dissolved, heated, or cooked.