Identify evidence of chemical changes, including color change, generation of a gas, solid formation and temperature change.
Distinguish between chemical and physical changes in matter.
Use the particle model of matter to explain how mass is conserved during physical and chemical changes in a closed system.
Recognize that acids are compounds whose properties include a sour taste, characteristic color changes with litmus and other acid/base indicators, and the tendency to react with bases to produce a salt and water.
MN Standard in lay terms:
Very rarely does matter not interact with other substances that it comes in contact with. Change is a constant even though it sometimes happens at a scale we cannot observe or at a rate we don't notice. As substances undergo changes, their properties may or may not alter depending on the nature of the change. Chemical and physical changes have profound effects on the our lives. If these changes take place within a closed container, then mass is conserved; meaning the mass of all substances before the change will be the same as all the substances after the change even though their identities may have changed.
This standard may be summarized in three key words: Changes, Systems and Conservation. If students come away with understanding how these three words connect with matter, they will be better prepared for re-engaging this content later in high school.
Changes in matter are taking place all the time. Reacting, melting, boiling, and dissolving are some of the language that describes these changes. Reacting implies a chemical change where new substances are being created which possess new sets of properties. Changes of state and dissolving are words that describe physical changes. These types of changes produce no new substances even though it might appear to.
Everything that happens does so in some type of system. Systems may be classified as either open or closed. This distinction is based on whether or not mass is conserved. If it is, then the system is referred to as a closed system
Conservation is a fundamental idea in describing how substances interact with other substances. Simply stated, the Law of Conservation of Mass states that mass cannot be created or destroyed in any chemical or physical change. Particles of one substance may or may not rearrange themselves as a result of contact with another substance, but the mass of the particles before the change must equal the mass of the particles after the change in a closed system.
MN Standard Benchmarks:
220.127.116.11.1 Identify evidence of chemical changes,including color change, generation of a gas, solid formation and temperature change.
18.104.22.168.2 Distinguish between chemical and physical changes in matter.
22.214.171.124.3 Use the particle model of matter to explain how mass is conserved during physical and chemical changes in a closed system.
126.96.36.199.4 Recognize that acids are compounds whose properties include a sour taste characteristic color changes with litmus and other acid/base indicators, and the tendency to react with bases to produce a salt and water.
- NSES Standards:
Substances react chemically in characteristic ways with other substances to form new substances (compounds) with different characteristic properties. In chemical reactions, the total mass is conserved. Substances often are placed in categories or groups if they react in similar ways; metals is an example of such a group.
Chemical elements do not break down during normal laboratory reactions involving such treatments as heating, exposure to electric current, or reaction with acids. There are more than 100 known elements that combine in a multitude of ways to produce compounds, which account for the living and nonliving substances that we encounter.
- AAAS Atlas:
- Benchmarks of Science Literacy:
The temperature and acidity of a solution influence reaction rates. Many substances dissolve in water, which may greatly facilitate reactions between them. 4D/M4
There are groups of elements that have similar properties, including highly reactive metals, less-reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon). 4D/M6a
An important kind of reaction between substances involves the combination of oxygen with something else-as in burning or rusting. 4D/M6b*
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
Materials vary in how they respond to electric currents, magnetic forces, and visible light or other electromagnetic waves. 4D/M9**
Substances react chemically in characteristic ways with other substances to form new substances with different characteristic properties. 4D/M11** (NSES)
If samples of both the original substances and the final substances involved in a chemical reaction are broken down, they are found to be made up of the same set of elements. 4D/M12**
The idea of atoms explains chemical reactions: When substances interact to form new substances, the atoms that make up the molecules of the original substances combine in new ways. 4D/M13**
Common Core Standards (i.e. connections with Math, Social Studies or Language Arts Standards):
Minnesota's newly revised (2010) English Language Arts (ELA) standards set K-12requirements not only for ELA but also for literacy in history/social studies, science and technical subjects.
188.8.131.52 Follow precisely a multistep procedure when carrying out experiments, designing solutions, taking measurements, or performing technical tasks.
184.108.40.206 Determine the meaning of symbols, equations, graphical representations, tabular representations, 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.
220.127.116.11 Compare and integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, table, map).
18.104.22.168 Distinguish among claims, evidence, reasoning, facts, and reasoned judgment based on research findings, and speculation in a text.
22.214.171.124 Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.
In conducting investigations on the chemical/physical changes taking place in matter, conservation of mass and acid/base chemistry, students will need to be able to interpret and support their findings through the use of content-specific language and representations (graphs, tables, etc.) of the data that they have collected. They will need to also use these tools to evaluate the data and information of others, including that found in related texts.
Middle- and high-school student thinking about chemical change tends to be dominated by the obvious features of the change. (Driver, 1985) For example, some students think that when something is burned in a closed container, it will weigh more because they see the smoke that was produced. Further, many students do not view chemical changes as interactions. They do not understand that substances can be formed by the recombination of atoms in the original substances. Rather, they see chemical change as the result of a separate change in the original substance, or changes, each one separate, in several original substances. For example, some students see the smoke formed when wood burns as having been driven out of the wood by the flame. (Andersson, 1990)
Beyond Appearances: Students' Misconceptions About Basic Chemical Ideas: An extensive compilation from the Institute of Education at the University of London, this document looks at misconceptions in chemistry and connecting concepts, including chemical reactions.
The standard in action with a student-centered classroom
Out in the schoolyard, Ms N's students watched with rapt attention as she performed the "Coke and Mentos" experiment. After the fountain of Diet Coke faded, she pulled out her portable white board and asked students, "We have been talking about properties of matter, physical changes, and introduced the idea of a chemical change. What did you just see just now? A physical or a chemical change? Let's record your ideas on the white board. "Definitely a chemical change", said Brandon. "The mentos reacted with the Diet Coke and caused the explosion!" "No", countered Kaitlyn, "The fizz is already in pop. Dropping the Mentos in the bottle just pushed it out." After students had finished sharing ideas, Ms N. put down her marker and said, "We have a lot of different responses here. It looks like we need to take a closer look at physical and chemical changes to narrow down our thoughts. Let's go back in and see if our lab can help us out."
"Grab enough goggles for your group", shouted Ms N., "then find your seats". Students scrambled to get their science notebook and goggles, then settled into their groups. "I'd like you to take a few minutes with your group and come up with a list of things in your notebooks that you think would be evidence of a chemical change. While you are doing that, I am going to project the lab instructions on the board." The classroom soon buzzed with students talking and arguing about what would indicate a chemical change. "Okay, let's come back", said Ms N. after several minutes. "I am going to go over directions for the lab, so heads up. Each group is going to get a zipper bag, a small medicine cup, and some measuring spoons. You are also going to get two jars containing white powders, aptly called 'Powder A' and 'Powder B'. In addition, you'll be getting a bottle with a red liquid. There are some safety issues here, so make sure you don't taste anything and wear your goggles until we put the chemicals away. Take ¼ teaspoon of Powder A and measure out a ½ teaspoon of Powder B and add both to your plastic bag. Measure 5 milliliters of the red liquid into the medicine cup and carefully place it into the bag without spilling it! You are going to seal up the bag, and then tip the medicine cup over to mix the chemicals. Be ready to record your observations in your notebook. Go to it!"
Students got their supplies then quickly got started on the lab. "Whoa - look at this!", exclaimed Isaac. He held up his group's bag, which had inflated. "It feels cold! And it changed color", Logan said. Ms N. interrupted after a short time. "Let's put our materials aside for a minute and talk about what happened in this lab. I'd like a representative from each group to come up to the board and add something you observed. Every group needs to have something different up here." Students jostled to find a spot to write on the board, then took their seats. "How does the list of observations on the board compare with the list that you made earlier for evidence of chemical change?", asked Ms N. "They have a lot of the same stuff", Anna said. "Like, we said a chemical change would show fizzing or turn a different color and it did both in the lab". "But the temperature changed, too. We hadn't thought of that", said Sabrina. As students wrapped up their comparisons, Ms N. asked, "So... just a physical change or a chemical change? What do you think?" "Chemical!", students chanted, nearly in unison. "Give me some reasons!", implored Ms N. James explained, "Well, we all saw some sort of reaction happen. It wasn't like just changing state or anything. It turned out to be something that looked totally different. A chemical change is when you end up with something different than your started with - like you can't just get back what you had before."
Ms. N. wanted the class to go a little further, to better cement these initial ideas about chemical reactions and chemical change. "Now, we are going to repeat the experiment, but we are going to switch things up a bit. You are going to want to decide on a data collection table before you start, so make sure you talk that over with your group first. This time we are going to change a variable. You can leave out one of the chemicals that we used in the first experiment, or you can change the amount of one of the chemicals - make it more or less. You decide which variable that you would like to change. If you have time, feel free to do both, but get your notebook work done before you try the second option. Be sure to record all your data. I am going to want a summary of what happened in your experiment and I want you to make a claim as to whether you are seeing a chemical change. I'll be looking for you to back that up with evidence from your observations. Give it a whirl!"
The vignette here does a nice job of illustrating a plausible sequence of activities to construct an engaging learning sequence in your classroom. Chemical changes are great hooks to getting minds-on in your classroom. This can be done via video clips, teacher-demonstrations and/or student directed lab explorations. Exploring chemical and physical changes should build on what students already know. It is important here to determine what these ideas are. One of the Keeley formative assessment probes would allow you insight into these ideas and also help in the planning process for this standard. These probes could also lead to actual student-designed inquiries about nails in jars or ice melting in a bag. Identifying and confronting misconceptions in your classroom is not a process, but rather it is an event. Students hang onto their flawed ideas more strongly than we often realize.
When working with conservation of mass activities, mass is a measurement that is key to what gets constructed in student's minds. For this reason, it helps to ensure that mass measurements are as precise and accurate as possible. If electronic balances are available, by all means use them. Typical middle school triple-beam balances will provide measurements that possess more uncertainty. This will force more of your post-lab conversation time to be about student error instead of on the conservation principles being examined.
There is also great value in providing students multiple opportunities to connect this content with their everyday lives. Asking questions about ways our lives are influenced by chemical changes and physical changes or what % of the food we eat is acidic or basic provide opportunities for discussions at home and for richer discussions in your classroom. The greater the awareness of the ways we are impacted by changes in matter, the better engagement and buy-in you will get from your students. Your classroom activities will be viewed as relevant, leaving you to work with the rigor.
Since the labs you will do for this standard will involve chemicals, make sure you read through the MSDS material available so that you may communicate any safety concerns to your students. It would be a great time to talk about safety procedures again. Flinn Scientific has a very detailed safety contract that probably goes beyond the scope of 8th grade science, but is still helpful to examine. Flinn also has a comprehensive list of safety resources for teachers that can be accessed here.
Since this is an area where you might feel that your content background is inadequate, it is important that you develop a support network where your content questions may be asked and answered in timely manners. This network will look different for different people, but it is very important that it develop. It is unreasonable to expect yourself to have the answers for every question that comes up in your classroom. Just Ask Antoine is a website out of Frostburg State University that offers an place to pose questions to it's chemistry department.
This simple activity provides a chance for students to classify common everyday activities as examples of chemical or physical changes. This activity would be most effective when groups of students are working in pairs on the classification activity. Middle School Science (2008) 126.96.36.199.1, 188.8.131.52.2
This activity provides students with an opportunity to draw a cartoon to illustrate their understanding of what happens to water molecules as they change phase from solid to liquid, liquid to vapor, vapor to liquid or liquid to solid. Changes in Matter Cartoon activity (2009). 184.108.40.206.2
A very common lab activity done at this point in the curriculum is an observation activity regarding an unlit and lit candle. Birthday candles may be used in place of larger candles. Evidence of both physical and chemical changes may be observed in this activity. There are numerous versions of this activity available digitally. Here is a version retrieved from the Middle School Science website. 220.127.116.11.1, 18.104.22.168.2
In this lab, you will use the juice from red cabbage as a pH indicator to test common household liquids and determine their pH levels. This particular handout also contains some background information on the pH scale and how cabbage juice serves as an indicator. Red Cabbage Lab: Acids and Bases (2009) 22.214.171.124.4
In this demonstration, Steve Spangler demonstrates a number of different acid-base demonstrations before coming to cabbage juice. The site contains both text descriptions of what he does, along with a streaming video. Steve Spangler (2009) 126.96.36.199.4
Most conservation of mass lab activities involve the "cookbook lab" of adding vinegar to baking soda in a flask and then placing a balloon over the mouth of the flask to retain the volume of gas generated by the reaction. This lab activity demonstrates conservation of mass with polystyrene. Pieces of polystyrene are put in an oven, and t heir size and shape changes, but the mass stays the same. Students measure the size of the plastic pieces before and after heating and compare to help understand conservation of mass. This activity is is found on the Materials Information Society website. 188.8.131.52.3
An inquiry-based example of conservation of mass is an activity that uses popcorn. Pietrangelo M. (2010) asks students design a procedure to determine the percent of water in different brands of popcorn as they play the role of food chemists. It might be wise to substitute the use of Bunsen burners with hot plates for this activity. 184.108.40.206.3
Additional resources or links:
A concise summary of the particle model on Tutorvista. This idea is essential in explaining changes of state and conservation ideas.
Conservation of Mass is an idea that is traced back to Antoine Lavoisier. Wikipedia contains a detailed summary of his life and accomplishments.
The American Chemical Society (ACS) provides a number of resources that will provide content help or content enrichment for this standard. Their book, Inquiry In Action is available online and contains background information to help you facilitate content discussions in your classroom. ACS also publishes a magazine called Chemmatters that provides stories about applications of chemical technology that could be used for enrichment in the 8th grade.Subscription information and archived issues can be found here.
Physical Change: involves a change in physical properties, but not in chemical properties. Physical properties can be observed without changing the composition of matter. Examples of physical properties include: texture, shape, size, color, volume, mass and weight.
Chemical Change: Connections between atoms are broken and new connections are made with different atoms resulting in new substances which possess different properties than the original substances.
Chemical Reaction: Interactions between substances (elements or compounds) in which there is a change in the chemical composition of the substances (elements or compounds) involved.
Conservation of Matter: The mass of an closed system cannot be changed as a result of processes acting inside the system. A similar statement is that mass cannot be created/destroyed, although it may be rearranged in space, and changed into different types of particles. This implies that for any chemical process in a closed system, the mass of the reactants must equal the mass of the products.
Closed System: This describes a system that may exchange energy with it's surroundings, but not matter.
Open System: In contrast with a closed system, this system is free to exchange energy and matter with its surroundings. It will not obey conservation principles.
Particle Model: A scientific model used to explain the composition and behavior of matter. It is used to explain the differences between solids, liquids and gases.
Acid: An acid in common usage is a substance that tastes sour, reacts with metals and carbonates, turns blue litmus paper red, and has a pH less than 7.0 in its standard state.
pH: A scale from 0 to 14 used to measure the acidity of an aqueous solution. It measures the concentration of hydrogen ions in the solution. pH values less than 7 are considered acidic, values greater than 7 are considered basic and values equal to 7 are neutral.
Base: A substance that is water soluble, bitter tasting, turns red litmus paper blue and has a pH greater than 7.
Having a source of short video clips at your disposal is an effective way of breaking up or emphasizing certain parts of the content. This is a collection of videos from Steve Spangler, one of which was highlighted in the selected activities. How Stuff Works also contains an extensive video library that is freely available online. Science Hack contains another video collection that is claimed to be screened by scientists. 220.127.116.11.1, 18.104.22.168.2, 22.214.171.124.4
Explore Learning: Gizmos Gizmos offers many computer simulations that are useful for students initially investigating a hard-to-visualize concept or in situations where an actual lab would be difficult to perform. Many of the Gizmos allow students to manipulate variables to see how that affect the outcome of the investigation. There are two phase change and two acid-base gizmos that could be used to help students conceptualize this these benchmarks. This is a subscription website, but free 30 day memberships are available. 126.96.36.199.3, 188.8.131.52.4
A WebQuest is an inquiry-oriented lesson format in which most or all the information that learners work with comes from the web. They provide opportunities for meaningful collaboration between students as well. There is a wealth of information available digitally and constructing lessons to access this information can help you to ensure that the ways technology is used in your classroom remains relevant. Constructing and designing quality webquests is a learned skill. WebQuest.org contains a helpful tutorial page to assist you in building a webquest. Here is an example of a matter webquest could look like thanks to a middle school science teachers in Georgia. 184.108.40.206.1
The American Chemical Society (ACS) has a number of animations available online to help students visualize some of the processes taking place within the content covered in this standard. ACS hosts the Middle School Chemistry website where these mutimedia and lesson ideas are found.
Being that this standard is a physical science standard being taught in an earth science course, it is important that these standards be seen as part of the course curriculum and not as an add on unit. This standard fits well with Minnesota Science Standard 220.127.116.11 and 18.104.22.168. Both of these standards incorporate the idea of weathering. In earth science, weathering involves chemical and physical processes which can be connected to the chemical and physical changes being studied here. The fact that chemical processes produce new substances can also be applied to the rock cycle (22.214.171.124) to explain how one type of rock may be changed into another type of rock. Chemical changes also play a significant role in the development of fossil fuels deposits and natural ore bodies that are mined here on earth (126.96.36.199.2) Finally, acid/base chemistry easily connects with discussions involving the environmental implications of acid rain and its role in the water cycle (188.8.131.52.2). Acid chemistry may also connect with the development of karst topography here in Minnesota and elsewhere (184.108.40.206.1)
A formative or summative evaluation question suitable for assessing student understanding of this standard.
A class observes two demonstrations: water changing into steam and a piece of wood burning and producing smoke. A student concludes that both demonstrations must be examples of a chemical change because a gas is produced in each.
Is the student's conclusion accurate? Explain your answer, referring to both demonstrations.
Keeley, P. (2005). Uncovering student ideas in science, volume 1. Arlington, VA: NSTA Press.
A number of probes in this volume relate to chemical and physical change. "Ice Cubes in a Bag" (p.49) deals with conservation of mass and closed systems. "Seedlings in a Jar" (p.67) and "The Rusty Nails" also relate to conservation of mass and chemical changes. All three of these formative assessments could be taken further by having students actually perform the tasks in the classroom, thereby testing their initial ideas.
Keeley, P. (2009). Uncovering student ideas in science, volume 4. Arlington, VA: NSTA Press.
"Burning Paper" (p. 23) lends itself to be done as a teacher demonstration (for safety reasons), as well as an initial assessment of student understanding of the concepts of conservation of matter, closed systems, and chemical change. "Nails in a Jar" (p.31) also deals with conservation of mass in a closed system, as well as chemical change. It could also easily be incorporated as a classroom demonstration or mini student lab investigation.
How can the concepts of chemical and physical changes, conservation of mass and acid-base chemistry be threaded seamlessly throughout the eighth grade science curriculum?
What are the essential questions students need to answer to demonstrate an understanding of this standard?
What questions do I have about this standard and where can I go to get help?
There just might be some booms and odors coming from this classroom. Students should be working with chemicals to understand the changes that take place when they interact with each other. Proper safety procedures should be in evidence; students wearing goggles, materials being disposed of appropriately, etc.. Students would be involved with making observations and taking measurements with would be entered into lab notebooks. Students should be able to verbalize essential questions that are guiding their learning. Students could diagram for you what they believe to be happening when matter undergoes physical or chemical changes.
Snow, D. (2003). Noteworthy perspectives: Classroom strategies for helping at-risk students (rev. ed.). Aurora, CO: Mid-continent Research for Education and Learning.
In 2002, McREL conducted a synthesis of recent research on instructional strategies to assist students who are low achieving or at risk of failure. From this synthesis of research, McREL identified six general classroom strategies that research indicates are particularly effective in helping struggling students achieve success:
Whole-class instruction that balances constructivist and behaviorist strategies
Cognitively oriented instruction which combines cognitive and meta-cognitive strategies with other learning activities
Small groups of either like-ability or mixed-ability students
Tutoring that emphasizes diagnostic and prescriptive interactions
Peer tutoring, including classroom-wide peer tutoring, peer-assisted learning strategies, and reciprocal peer tutoring
Computer-assisted instruction in which teachers have a significant role in facilitating activities
Complete results of this study may be downloaded here.
This page contains strategies to help teachers better attend to the needs of their ELL learners. These strategies are grouped according to the following learning tasks: listening, visualization, interpersonal communication, laboratory, demonstrations, reading and writing, instruction and vocabulary.
Klentschy, M. (2010). Using science notebooks in middle school. Arlington, VA: NSTA Press.
Front-loading: Teachers plan for words that ELL students will encounter as they do inquiry and within the particular content being studied. They need to provide not only experience with vocabulary words (the "bricks"), but also the form and context in which they are used in spoken or written language (the "mortar").
Word Wall: The teacher writes and discusses the needed vocabulary and posts the words on chart paper, sentence strips, or the board, making sure they remain in clear view for students to use as a resource when writing or speaking.
Kit Inventory: Uses science materials from the current lesson, allowing students to question and discuss the scientific name of these items, their use, and description of the properties of those materials (made of plastic, cylinder-shaped, etc.) in their investigations.
Everyday Words and Science Words: Purposely contrast the meaning of everyday words and science words (For example: "write down" versus "record"). These could be recorded on a chart for student reference.
Sentence Stems: Use abbreviated stems or scaffolds to help students begin writing in their science notebooks about their inquiry investigations:
I observed _____.
I wondered _____.
I thought _____ would happen.
Today I learned _____.
Questions I have now _____.
Charts: Teachers should model a variety of charts and how to use them for recording and reading information. This helps students to have examples for eventually making their own charts, as well as to successfully use the vocabulary as it is presented in context.
Diagrams and Illustrations: Labeling diagrams, particularly those that the students drew themselves, reinforces the use of vocabulary and allows students to make relational connections to content.
Classification: Classification (which could include sorting, use of Venn Diagrams, T-charts, etc.) allows students to develop their understanding of the similarities and differences of (in this case) substances and to further interact with content specific words within the course context.
CLOZE: This strategy involves providing students with a reading passage in which content specific vocabulary (the "brick" words) have been left out. Words to include could be selected from a word wall or chart.
Concept Maps: Rather than merely learning recognition and definitions of science vocabulary, developing a concept map over the course of a unit helps students to tie those words into networks of related concepts. Maps can be added to as the unit and the understanding develop, possibly adding new ideas or connections in a different color.
Teachers First is a educational support website that contains a list of strategies for working with gifted and talented students in your classroom. Many times it is not your "A" student that qualifies as Gifted and talented, but rather the student who is not achieving and being disruptive.
Cogito is a website set up as an online community for gifted and talented students. There is a link to their chemical sciences page that provides information designed it to capture and highlight all the interesting conversations, articles, experts, and activities going on around the chemical sciences on Cogito.
Students With Disabilities is a position statement by the National Science Teachers Association concerning the inclusion of and basic adaptations for students with disabilities in the science classroom.
Many of the adaptations listed below for ELL students also work well for special education students.
Technologies for Special Needs Students: In their newsletter, "Tech Trek", from the National Science Teachers Association, suggestions are given for using various technologies to make science more accessible to students. Included are ideas for computer-assisted instruction, assistive technologies (such as voice-recognition software), as well as internet links and additional resources.
You could develop some simple take home activities about chemical/physical changes or provide students with some strips of litmus paper to test the acid/base character of some of the cleaning and food products at home. Asking students to make a list of all the chemical or physical changes taking place in their home might provide opportunities to have scientific conversations at home. All resources you use in class need to be accessible by parents and students from home, assuming they have a viable connection to the Internet. Using a district sponsored website like Moodle or Schoolwires provides access for families to relevant and current information for your course.