Solutions

Chemistry Assessment
Eligible Texas Essential
Knowledge and Skills
Texas Education Agency
Student Assessment Division
September 2010

Readiness standardshave the following characteristics.
They are essential for success in the current grade or course.
They are important for preparedness for the next grade or course.
They support college and career readiness.
They necessitate in-depth instruction.
They address broad and deep ideas.
September 2010

Supporting standardshave the following characteristics.
Although introduced in the current grade or course, they may be emphasized in a subsequent year.
Although reinforced in the current grade or course, they may be emphasized in a previous year.
They play a role in preparing students for the next grade or course but not a central role.
They address more narrowly defined ideas.
September 2010

TEA is implementing a number of changes that should serve to test knowledge and skills in a deeper way.
Tests will contain a greater number of items that have a higher cognitive complexity level.
Items will be developed to more closely match the cognitive complexity level evident in the TEKS.
In science, process skills will be assessed in context, not in isolation, which will allow for a more integrated and authentic assessment of these content area.
In science, the number of open-ended (griddable) items will increase to allow students more opportunity to derive an answer independently.
September 2010

Solutions

Prior Knowledge - Solutions
Water is polar
Vocabulary:
Solute
Solvent
Saturated
Unsaturated
Supersaturated
Precipitate
Electrolyte
Nonelectrolyte
Write a formula
Balance an equation
Write a balanced equation
Calculate moles

Engage
Water + Alcohol
KI + Pb(NO3)2
Chemical Music Video – “For Those About to Dissolve, We Solute You”
Sodium acetate supersaturated solution

What should be taught…
Water is polar
Water is less dense as a solid than a liquid
Vocabulary:
Soluble
Solute
Solvent
Saturated
Unsaturated
Supersaturated
Electrolyte
Nonelectrolyte

Which factor makes water an effective solvent?

F the presence of molecular oxygen
G its lack of covalent bonds
H the polar nature of its molecules
J its abundance on Earth’s surface
Fish survive through severe winters because of the property of water that allows water to -

F form chemical bonds as it freezes, raising the water temperature below the ice
G increase in density while it freezes, dissolving more oxygen from the air
H expand when it freezes, creating a floating and insulating layer of ice
J precipitate vital nutrients when it freezes, increasing the food supply

The diagram on the right shows water molecules and ions from an NaCl crystal. What is the most likely reason that each water molecule is arranged so that the oxygen part of the molecule faces a sodium ion?

F The oxygen in a water molecule contains a partial negative charge.
G Gravity rotates the oxygen atoms to face the more-massive sodium ions.
H Hydrogen atoms create repulsive forces with chloride ions.
J Oxygen atoms form covalent bonds with sodium ions.

Solubility Curves
Use the graph to answer the questions.
1. If there are 45 grams of KCl in 100 g of H2O at 30 oC, the solution will be
a. unsaturated
b. saturated
c. supersaturated
2. How many grams of KNO3 will dissolve in 100 g of H2O at 50 oC to make a saturated solution?
3. If there are 10 grams of KNO3 in 20 g of H2O at 40 oC, how many more grams of KNO3 must you add to have a saturated solution?

In this apparatus, the seawater is an example of a —

F strong electrolyte
G weak acid
H nonelectrolyte
J strong base

Solubility rules
Precipitate reactions
Factors that influence solubility and rates of solvation

What precipitate is formed when barium hydroxide is reacted with sodium sulfate?
What would you do to dissolve calcium chloride in water faster?

Molarity!!
Calculate dilutions of solutions

What is the molarity of a solution prepared by dissolving 40 g of sodium hydroxide in 2 L of solution?
If 50 mL of a 6 M hydrochloric acid solution is added to enough water to make 2 L of solution, what is the final molarity?

Prior Knowledge – Acids and Bases
Acid
Base
pH scale

Arrhenius acid / base
Bronsted-Lowry acid / base
Degrees of dissociation for strong and weak acids and bases
Acid-base reactions
pH scale
pH calculations

Which of the following is a Bronsted-Lowry base but not an Arrhenius base?
Mg(OH)2
NH3
NaOH
Sr(OH)2

What are the products of the reaction of sulfuric acid with potassium hydroxide?
What is the pH of a 2.3 x 10-3 M HCl solution?

This question could be adapted to address strong vs weak acids/bases.
In this apparatus, the seawater is an example of a —

F strong electrolyte
G weak acid
H nonelectrolyte
J strong base

Solutions

by Paul Schumann

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