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Paul Caginalp |
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Chemistry |
Grades 10, 11, 12 |
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Regents |
2/25-3/5 |
Solutions unit
Abstract: The unit includes solid, liquid, and gaseous solutions. The focus however, is on liquid solutions. Colligative properties, solubility curves, measures of concentration, and factors affecting solubility will all be examined. The unit will start with vocabulary, and a general conceptualization of what the vocabulary does for the unit. As we move along the students will become more adept at using the vocabulary, and will be able to tackle the ideas of factors in solubility, dissociation equations, solubility curves, concentration, and colligative properties in that order.
Topic list
Solutions
Factors affecting solubility
Gases versus Solids
Dissociation equations
Solubility products
Solubility curves
Concentration
Colligative properties
Vocabulary words
Solubility-The affinity or lack thereof for a solid or gas to dissolve.
Solute-The solid or gas (generally) that is added to the solution, or in the minority.
Solvent-The majority of a solution
Concentration-a measure of how dilute or concentrated a solution is
Saturated-the point where no more solute can be added to a solution
Dissociated-the tendency of ionic compounds to split into ions in a solution
Molarity-the most popular measure of concentration, given in moles per liter
Boiling Point elevation-the amount that a solutions boiling point raises after addition of a solute
Freezing Point Depression-the amount that a solutions freezing point drops after addition of a solute
Precipitate-the solute in a solution that is not dissolved
Electrolyte-any ion in solution that can carry electric current
Key Activities
Creative descriptions of vocabulary
Guided practice
I will
give the students time to practice needed skills in class by having them work on
worksheets while I can still guide them through a step if I need to. I will use this as my way of
transferring responsibility to the students.
Two Quizzes
Unit Test
Labs-One on saturated solutions, one on solubility curves, and one on concentration
Pieces of the real world
Examples of solutions; amalgams, alloys…
Freezing point depression with snow and ice on roads
Soda bottles, and the solubility of carbonation
Electrolytes in the body
Big Ideas
The most important ideas for this unit for these kids are what is going to be tested on the regents. The most common questions for solutions on the regents are on the factors affecting solubility, the solubility curves, and molarity. I also plan to include the reasons for dissociation as one of my big ideas, but other than that I will stick fairly close to the big ideas that the regents identifies. The students will be able to tell what will happen if a solution is heated, pressurized, or stirred. They will also be able to read solubility curves. The solubility curves are easy to read, but they have to watch out for how much water the question dictates. Solubility curves are made at 100g of water. If more water is present, more solute can be added. For molarity they to be able to convert easily from moles to liters, and back. Understanding the reason for dissociation is a little harder, but I think they can manage it. They need to realize that water molecules are polar, and that the polar molecules are what pulls the ionic crystals apart.
Standards and objectives:
Mixtures are composed of two or more different substances that can be separated by physical means. When different substances are mixed together, a homogenous or heterogenous mixture is formed.
Proportions in a mixture can be varied. Each component in a mixture retains original properties.
A solution is a homogenous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical nature of the solute and solvent.
Concentration of a solution may be expressed as molarity percent mass, or parts per million.
The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. The greater the concentration of solute particles the greater the effect.
Students will be able to answer regents questions about solutions
Students will be able to identify solutions, and describe their properties.
Students will be able to explain
why a pickle lights up and a cucumber doesn’t in terms of electrolytes and the
properties of solutions.
Central question and Concept Map
In what different ways do compounds mix? What difference does it make?
Mercury alloy
Type of solid solution
Non
heterogeneous mixture
Phase of solution
Homogenous mixture
Phase of
Solution
Factor of
solubility
Phase of
solution
Factor of solubility
known traits
Factor of
solubility
known traits
important effect
on ionic solids
Determines the extent
of dissociation
measure of solids
in solution One type of
dissociation
Effect of ions in
solution
Assessment
For preassessment I want the students to make the vocab their own. I plan to do this by letting them creatively display their ideas of the vocab. I want them to come up with a picture, song, activity, sculpture, or other way of demonstrating a vocab word. They will work in groups of 3-4 and each group will be assigned 2-3 words. They will then have 15 minutes to be creative, using whatever they can find in the room. This should air any misconceptions, as well as providing an interesting way for them to learn the vocab. It is my hope that this will get them to the comprehension stage of Blooms taxonomy. I think that this understanding will carry through this unit because this unit is based heavily on vocab. This should enable students to identify solutions and their properties, and answer regents questions. To make sure my students achieve these objectives, I will give them a test at the end of the unit that consists of half regents questions, and half of my own questions. The purpose of this is to get them accustomed to the types of questions that the regents asks while still asking good questions.
Another preassessment task is to electrify a pickle and a cucumber, and not provide the answer of why the pickle lights up till a day later. This provides them time to reason it out, and time to get really anxious to know the answer. I will either do this the first day of the unit, or the second, depending on how well the creative group does with the term electrolytes. I will use this to lead into a small discussion of how electrolytes affect our bodies and why Gatorade has them. The cumulative assessment for this objective will be in the test, as one of my questions.
Finally, to help students pick out solutions and their properties, I am starting them off with a homework assignment to pick out and categorize 8 solutions that they can find at home. They will then group with a partner in class, and discuss the solutions they picked and categorized with regard to accuracy. The final assessment for this objective will come in the form of a lab, as the students attempt to make their own solubility curve.
This will force them to make their own curve for a substance, see what factors affect solubility, and how their substance acts.
Learning cycle patterns
The first assessment listed above fits the learning cycle well. I plan to model the first vocab word creatively. The word that I have chosen to do this with is molarity. I plan to make a sculpture o’ molarity. I have a 1L soda bottle, and a stuffed mole that I will place atop it. Moles per liter. The next vocab word, solubility, I plan to enlist the students help in showing. I will ask for suggestions, and then when we have finished I will ask them to help me rate it for effectiveness. By asking them to rate it for effectiveness and accuracy I hope to ensure that their group examples will be rated as well. Based on how well they are taking to the subject, I will either turn them loose to their own creative devices, or do another example with their input, but less of my input. The other place I expect to do a complete learning cycle is with solubility curves. The students will be doing questions on solubility curves by day three of the unit. These questions are fairly easy to answer, with one or two tricks thrown in to make the kids read carefully. I will model a question, and show them the pitfalls of not reading carefully in a second example, but then I expect them to do it on their own. The responsibility for solubility curves will be wholly theirs when they have completed their lab on solubility curves, which could take place anywhere from the first, to third day of the unit. (they do the lab then, but they don’t hand it in till the next week, which should be past the solubility curve day.)