Describe a system, including specifications of boundaries and subsystems, relationships to other systems, and identification of inputs and expected outputs.
For example: A power plant or ecosystem.
Describe the dynamic process by which solutes dissolve in solvents, and calculate concentrations, including percent concentration, molarity and parts per million.
Explain the role of solubility of solids, liquids and gases in natural and designed systems.
For example: The presence of heavy metals in water and the atmosphere.
Another example: Development and use of alloys.
MN Standard in Lay Terms
Solutions are composed of a solute that is dissolved in a solvent.
A solution can be all states of matter; gas in liquid, solid in liquid, etc.
The ratio of solute and solvent or solution determines the concentration.
Solutions are made up by a solute (lesser amount) dissolving in a solvent (greater amount)
Solutions can consist of solutes and solvents that are solids, liquids, or gases
Concentration is the measure of the ratio of the solute to a given amount of solvent or solution
percent concentration = mass of solute / mass of solution x (100)
Molarity (M) = moles of solute / liters of solution
parts per million (ppm) = mg solute/ liters of solution or mg solute / kg solution
Solubility of a substance is determined by the nature of the solvent and solute.
Temperature and pressure may influence solubility.
MN Standard Benchmarks
184.108.40.206.1 Describe a system, including specifications of boundaries and subsystems, relationships to other systems, and identification of inputs and expected outputs. For example: A power plant or ecosystem.
9C.220.127.116.11 Describe the dynamic process by which solutes dissolve in solvents, and calculate concentrations, including percent concentration, molarity and parts per million.
9C.18.104.22.168 Explain the role of solubility of solids, liquids and gases in natural and designed systems. For example: The presence of heavy metals in water and the atmosphere. Another example: Development and use of alloys
A Framework for Science Education (preliminary draft) - National Research Council (NRC)
PS1: Macroscopic states and characteristic properties of matter depend on type, arrangement and motion of particles at the molecular and atomic scales.
Mixtures and Solutions (page 167)
- NSES Standards:
12BPS2.4 The physical properties of compounds reflect the nature of the interactions among its molecules. These interactions are determined by the structure of the molecule, including the constituent atoms and the distances and angles between them.
- Benchmarks of Science Literacy
An enormous variety of biological, chemical, and physical phenomena can be explained by changes in the arrangement and motion of atoms and molecules. 4D/H7b
The configuration of atoms in a molecule determines the molecule's properties. Shapes are particularly important in how large molecules interact with others. 4D/H8
Some atoms and molecules are highly effective in encouraging the interaction of others. 4D/H9b
The physical properties of compounds reflect the nature of the interactions among its molecules. These interactions are determined by the structure of the molecule, including the constituent atoms and the distances and angles between them. 4D/H10
Systems - pages 262-266
A system usually has some properties that are different from those of its parts, but appear because of the interaction of those parts. 11A/H1
Systems may be so closely related that there is no way to draw boundaries that separate all parts of one from all parts of the other. 11A/H5** (SFAA)
Research Base: Structure of Matter, pages 336-337
Structure of Mat
ter: Volume 1 (blue) pages 54-59
Atoms and Molecules
Conservation of Matter
States of Matter
COMMON THEMES - Systems: Volume 1 (blue) pages 132-133
Chapter 9: Solids, Liquids and Gases (Dissolving pages 83-84)
Chapter 11: Particles (Particle Ideas about Solution page 95)
Chapter 12: Water (pages 98-103)
The authors help you to understand the ideas-right and wrong-that your students have already developed-and to teach in a way that takes their learning perspectives into account.
Common Core Standards
2010 Literacy Standards - Reading Benchmarks: Literacy in Science and Technical Subjects 6-12
Integration of Knowledge and Ideas Benchmark 22.214.171.124 Integrate and evaluate multiple sources of information presented in diverse formats and media (e.g., quantitative data, video, multimedia) in order to address a question or solve a problem.
Language Arts Standards: Students can write a laboratory report in the proper form and using their knowledge of technical writing skills.
RST.9-10-1. Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or directions.
RST.9-10-2. Determine the central ideas or conclusions of a text; trace the text's explanation or description of a complex process, phenomena or concept; provide an accurate summary of the text.
RST.9-10.3. Follow precisely a complex multistep procedure when carrying out experiments; taking measurements or performing technical tasks, attending to special cases or exceptions defined in the texts.
- Many students think solvents must be liquids.
- Some students will believe amount of solution is proportional to the molar concentration.
- When a colorless solute dissolves in water, it is easy for students to think that it "disappeared" without understanding the nature of dissolution.
- Students don't always realize that dissolving is a physical process and not a chemical reaction.
- Dilute and Concentrated are often confused with Weak and Strong
"Today," says Mr. Aqua, "we're going to investigate whether or not bottled water is worth the billions of dollars people spend each year because 'tap water is so bad for us'." He has the students break into five groups and gives each group a different article to read, each on a different color of paper. The students also have a set of questions specific to each article to be sure they make note of some of the most important aspects in the article. The articles are from current news reports from local papers as well as from the latest issue of Chemmatters. (See list below vignette for ideas.) After students have finished the reading, Mr. Aqua has the groups come together and discuss the questions as he wanders the room observing the conversations. The objective is that the group discussions lead to some consensus of the important aspects of the topic as well as bring some controversies to light using the diversity of the group members. "I want you to think about what you read and talked about today and give some thoughts to how this has any meaning in your life at home." The following day, the students get into groups with one person of each colored article. Mr. Aqua hands out a set of prompts for each student to cover as he/she summarizes the article. Later, the class discusses the issues - although there are disagreements and no one answer comes about, it is clear to see the students are taking some ownership in ideas behind the current uses of water and using plastics to bottle it. Benchmark 9C.126.96.36.199 - Explain the political, societal, economic and environmental impact of chemical products and technologies. For example: Pollution effects, atmospheric changes, petroleum products, material use or waste disposal.
The lab that follows is a dilution lab using the ppm and ppb as the measuring quantity. The students start with straight food coloring and do a 1 to 10 dilution several times and use powers of ten to calculate concentrations. Although chemistry often uses molarity, it is important to show students that environmentally, the measurement for an allowable amount of chemical in water or air is parts per million or billion depending on the substance and safety levels. Using the results, Mr. Aqua is able to show the idea of saturated and dilute versus unsaturated and concentrated, an idea many students get confused by. The class also notices that even though the liquid looks completely clear, there are particles of the solute still present in the solution. This can be transferred into the idea of particles in the atmosphere and leads nicely into the fact that solutions are made of all states of matter, not just solid in liquid.
"Alright," says Mr. Aqua, "take a look." The class is intrigued as a can of diet coke is placed in an aquarium along with regular coke. While one sinks the other floats. Using density, solutes and solvents, Mr. Aqua shows the students how slight changes within solutions can change certain properties. He challenges the students to make a golf ball float in a solution each pair of kids designs. Given a list of possible solvents and possible solutes, they use their knowledge about solubility, temperature, and concentration to get a golf ball to float in a clear container. Depending on the level of students in the class, it is possible to use quantitative measurements and calculations to make predictions before doing the investigation.
As a final activity, Mr. Aqua has the students make ice cream. With the higher mathematical students, he has them calculate what how much sodium chloride will reduce the temperature by a particular value. For the class where the focus is more conceptual, the students will note that the freezing point of the ice is actually below zero. To finish up the lab, Mr. Aqua has the class read "Salting Roads - The Solution for Winter Driving" from Chemmatters.
For the assessment on this particular unit, the students build a snow globe. A successful falling snow scene is equivalent to passing a test. Article from The Science Teacher (there are several variations of this activity)
Much of the information in these benchmarks is descriptive and shows up throughout the year. Molarity is often introduced during stoichiometry and acids and bases. Using water and the environment helps students see that the concepts studied in science class affect them on a daily basis and they need to understand them to be able to be good stewards of the resources of the earth.
Suggested Labs and Activities
a. Solubility Curve Lab
1. PhET Simulation: Salts and Solutions - Add different salts to water, then watch them dissolve and achieve a dynamic equilibrium with solid precipitate. Compare the number of ions in solution for highly soluble NaCl to other slightly soluble salts. Relate the charges on ions to the number of ions in the formula of a salt. Calculate Ksp values.
2. Save a Life - Clean Some Water - Student teams practice the measurement of water quality through turbidity and coliform bacteria counts. They use their results and information about water treatment processes to design prototype small-scale water treatment system models. They test the influent and effluent (outgoing) water to assess how well their model systems might prevent water-borne diseases and illnesses. (Nature of Science and Engineering standard 188.8.131.52.1. Describe a system, including specifications of boundaries and subsystems, relationships to other systems, and identification of inputs and expected outputs.)
3. Chemmatters Selected Articles for Solutions - April issues have a focus on environmental issues in chemistry. Several articles deal with water (treatment, pollution, conservation of). All issues have a teachers guide with questions and extra background on each topic.
d. Hot and Cold Packs - Explains how different hot and cold packs used for injuries use chemistry to create or absorb heat. Demonstrating the actual items in class can add to student understanding.
Also available: questions for reading
e. Salting Roads: The Solution for Winter Driving - Discusses freezing point depression and ions, compares salt to other de-icers in terms of number of particles formed when they dissolve. Also shows phase diagram for salt-water mixture. Describes new technology that also addresses highway safety in wintry conditions
f. Letting Off Steam - Information on the mechanics of geyser and hot spring formations that include deep earth heating of water which dissolves various molten rock (magma) minerals (silicon dioxide, calcium carbonate) that is brought to the surface to form solidified deposits. Other chemicals in an eruption include mercury, arsenic, hydrogen sulfide and carbon dioxide. Last page includes two student activities: making a volcano with soap, baking soda and vinegar, and boiling water at various temperatures with a vacuum filtration flask and a faucet with a suction filtration attachment.
Students Should Know and Be Able To Do:
Describe the process by which solutes dissolve in solvents.
Calculate concentration in terms of molarity. Use molarity to perform solution dilution and solution stoichiometry.
Identify and explain the factors that affect the rate of dissolving (e.g., temperature, concentration, surface area, pressure, mixing).
Compare and contrast qualitatively the properties of solutions and pure solvents (colligative properties such as boiling point and freezing point).
1. Videos - Online videos can be a great way to engage students at the start of a unit. A google search of key words in the content area can yield a variety of demonstration sites as well as full length videos.
a. Mr. Kent's Chemical Demonstrations - Several pages of well done you tube videos of various reactions to show using an LCD when materials are too dangerous or costly to perform experiments in class.
b. Exploscience.com - Dynamic Chemistry- This site has a series of videos in one place showing several demonstrations of solubility in action. It could be used to replace demonstrations if materials are not available or safety is an issue.
c. World of Chemistry Series - These videos are not modern but give a good foundation of basic information after the class has had some experience with the content. It can be used as a summary of the unit or possible review. Students could come up with a series of questions or use worksheets.
i.Water - properties of water and why this makes it an exceptional solvent
2. Science Literacy: Chemmatters - Published by the American Chemical Society, has relevant, fast reading articles to tie topics in the classroom to the real world of students. Teachers' guides with questions and additional background information are also available.
2. Using a classroom set of small whiteboards can help an instructor check for understanding. Having students sketch the graph of direct and inverse relationships as gas laws are studied is a good method of formative assessment if clickers are not available.
3. The "Best Practices" of Science Teaching - Many of the "so-called best practices" are summarized and examples are given in the chapter "Guided inquiry in the science classroom" by Minstrell, J. & Kraus, P. found in How Students Learn: History, Mathematics, and Science in the Classroom. (M. Suzanne Donovan and John D. Bransford, Editors) Washington, DC: National Research Council (2005). Other best practices are to be found in Robert Marzano's Classroom Instruction that Works.
This site has 15 minute podcasts for every topic in a general chemistry course. They are 15 minute segments posted on youtube for students to use independently or as a tutorial supplement for classroom instruction.
Normal Community High School Chemistry - Solutions - This website is designed as a service to teachers and as a forum for collaboration of high school teachers that want to improve the quality of their classrooms. This website posts only high quality material on a variety of topics which can be quickly downloaded and implemented into your classroom. In addition any collaborating teachers are welcomed and encouraged to post their own developed lesson plans
ChemTours developed specifically for Chemistry, 2nd Edition. These use animation and interactive exercises to help develop your understanding of fundamental concepts.
ChemChalkboard Great resource for many chemistry units, includes power points (many with animations), activities and labs
- soluble - ability of being dissolved
- solution - homegenous mixture of two or more substances in a single phase
- solvent - dissolving medium in a solution
- solute - substance dissolved in a solution
- alloy - solid solution in which the atoms of two or more metals are uniformly mixed
- solubility - is the amount of that substance required to form a saturated solution with a specific amount of solvent at a specified tempeature.
- concentration - a measure of the amount of solute in a given amount of solvent or solution
- molarity (M) - the number of moles of solute in one liter of solution
- molality (m) - the concentration of a solution expressed in moles of solute per kilogram of solvent
- parts per million (ppm) - mass ratio of the solute (pollutant) per million and the amount of solution
PHET simulation site. Various simulations to explore for states of matter and gas behavior. Works very well as a demonstration on an interactive white board. Many simulations are available in translated versions.
MN Math Benchmarks
184.108.40.206 Understand that quantities associated with physical measurements must be assigned units: apply such units correctly in expressions, equations and problem solutions that involve measurements (molarity calculations); and convert between measurement systems (percent concentration to parts per million).
220.127.116.11 Make reasonable estimates and judgements about the accuracy of values resulting from calculations involving measurements.
18.104.22.168 Use scatter plots to analyze patterns and describe relationships between two variables. Using technology, determine regression lines and correlation coefficients; use regression lines to make predictions and correlation coefficients to assess the reliability of those predictions. (solubility curves for various solutes - temperture vs. quantity) A solubility lab could be used to meet partial benchmarks in the algebra standard - linear relationships and calculator use.
Assessment of Students
You make yourself some juice by adding water to some frozen concentrate. What is the solute? What is the solvent?
a. water, juice b. juice, water c. water, water d. juice, juice e. cannot tell
1. How many moles of NaOH are contained in 65.0 ml of a 2.20 M solution of aqueous NaOH?
0.143 moles NaOH
2. You are given a mystery solution and asked to determine if it is unsaturated, saturated or supersaturated. Describe a test you could use to figure out what it is.
Drop a crystal of the solute into the solution. Dissolves = unsaturated, Nothing = saturated, Solidification = supersaturated.
3. Many of the chemicals that are considered dangerous to our environment only appear as very few parts per billion. If the number is so low, why would it matter?
All chemicals are different and can be dangerous in very small quantities. Something does not have to be concentrated to disrupt a system.
Assessment of Teachers
1. A student raises her hand and says that her elementary teacher tried to have the class make rock candy and it never worked. Why? Leading the class through what needs to happen to dissolve the sugar and in what quantity along with seeding the string could help the class identify what might have gone wrong during that activity. A challenge to the class to try this at home would be appropriate.
2. "This label says it is pure mountain water. How is this different than what comes out of the tap or a lake or a nearby river?" How would you get the class involved in a discussion about the different bottled waters and what the labels claim? What activities could you do? Have the class collect and bring in different labels. Have teams of students research different companies and the sources of water. Investigating pH, dissolved oxygen and water hardness will also produce varying results.
For certification in the content area, there is an online practice area for teachers for the PRAXIS chemistry test.
Struggling and At-Risk
Using demonstrations daily can engage most students and seeing them invites students to attend class regularly.
Mathematical relationships is typically not a strength.
Use dimensional analysis for molarity with lots of practice.
Parts per million is a hard concept to understand - dilution with colors helps them to visualize.
The science classroom is often a frustrating place for English language learners. Science has a complex vocabulary that is difficult even for native English speakers to learn. Difficulty learning English should not be confused with an inability to think scientifically. Many of the strategies that are useful for English language learners are effective for differentiating instruction for others.
Teaching Science to English Language Learners: Building on Students' Strengths - Can a student's cultural background support learning in science? Or is concentrating on the specialized vocabulary of science the best way to help English language learners learn science? This book addresses these and other pressing questions you face when working with students whose linguistic and cultural backgrounds, as well as their languages, are different from your own.
Anytime lessons and activities can be posted online ahead of time or shortly after help those students who struggle with note taking and organization.
Short quizzes often rather than one exam is necessary for limited math processing students.
This is an area where teachers should be using current environmental information and life examples to teach conceptual ideas. Students should be reading local newspapers, studying labels of food and beverages, and engaged in class discussions voicing differing opinions. Making ice cream could be considered a must if time is available!
There are many examples of solutions with varying concentration units around the home. Help your student find some common household products that are solutions with their concentrations. Have your student determine the "solute" and "solvent" for each. Examples would include household hydrogen peroxide (3 %), vinegar (5 %), rubbing alcohol (70%) and some cleaners such as Windex.