Solutions

Chemistry Assessment

Eligible Texas EssentialKnowledge and Skills

Texas Education AgencyStudent Assessment DivisionSeptember 2010

Readiness standards have 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.


Supporting standards have 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.


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.


Solutions

Solutions – Reporting Catgory 5: SolutionsOld TEKS New TEKS CCRS with performance indicators

(12) Science concepts. The student knows the factors that influence the solubility of solutes in a solvent. The student is expected to: (A) demonstrate and explain effects of temperature and the nature of solid solute on their solubility of solids; (B) develop general rules for solubility through investigations with aqueous solutions; and (C) evaluate the significance of water as a solvent in living organisms and in the environment.(13) Science concepts. The student knows relationships among concentration, electrical conductivity, and colligative properties of a solution. The student is expected to: (A) compare unsaturated, saturated, and supersaturated solutions; (B) interpret relationships among ionic and covalent compounds, electrical conductivity, and colligative properties of water; and (C) measure and compare the rates of reaction of a solid reactant in solutions of varying concentration.(14) Science concepts. The student knows the properties and behavior of acids and bases. The student is expected to: (A) analyze and measure common household products using a variety of indicators to classify the products as acids or bases; (B) demonstrate the electrical conductivity of acids and bases; (C) identify characteristics of a neutralization reaction; and (D) describe effects of acids and bases on an ecological system.

(10) Science concepts. The student understands and can apply the factors that influence the behavior of solutions. The student is expected to: (A) describe the unique role of water in chemical and biological systems; (supporting) (B) develop and use general rules regarding solubility through investigations with aqueous solutions; (readiness) (C) calculate the concentration of solutions in units of molarity; (supporting) (D) use molarity to calculate the dilutions of solutions; (supporting) (E) distinguish between types of solutions such as electrolytes and nonelectrolytes and unsaturated, saturated, and supersaturated solutions; (readiness) (F) investigate factors that influence solubilities and rates of dissolution such as temperature, agitation, and surface area; (readiness) (G) define acids and bases and distinguish between Arrhenius and Bronsted-Lowry definitions and predict products in acid base reactions that form water; (supporting) (H) understand and differentiate among acids-base reactions, precipitate reactions, and oxidation-reduction reactions; (readiness) (I) define pH and use the hydrogen or hydroxide ion concentrations to calculate the pH of a solution; and (supporting) (J) distinguish between degrees of dissociation for strong and weak acids and bases. (supporting)

E. Chemical reactions1. Classify chemical reactions by type. Describe the evidence that a chemical reaction has occurred. a. Write equations for chemical reactions using appropriate symbols and balance the equations by applying the Law of Conservation of Mass. Write net ionic equations. d. Use solubility rules to determine the precipitate formed in a double replacement precipitation reaction.2. Describe the properties of acids and bases and identify the products of a neutralization reaction. a. Define pH and describe acid and base solutions in terms of pH. Use hydrogen ion or hydroxide ion concentrations to determine the pH of an acid or base solution. b. Use both commercial and non-commercial indicators to identify acid, base, and neutral solutions in a lab experiment. c. Distinguish between Arrhenius and Bronsted definitions of acids and bases. Identify conjugate acid-base pairs. d. Describe how a titration is performed and how this process can be used to determine the concentration of an unknown acid or base solution. e. Measure and compare the pH of various common acids and bases (e.g., household cleaners, vinegar, citrus juice).I. Properties and behavior of gases, liquids, and solids.2. Understand properties of solutions. a. Describe factors affecting solubility, units of concentration, colligative properties, and colloids. b. Calculate the molarity and molality of solutions. c. Determine boiling point elevation and freezing point depression for a solution.

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 + AlcoholKI + Pb(NO

3 )2

Sodium acetate supersaturated solution

Chemical Music Video – “For Those About to Dissolve, We Solute You”

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 oxygenG its lack of covalent

bondsH the polar nature of its

moleculesJ 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 CurvesUse 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. unsaturatedb. saturatedc. 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 electrolyteG weak acidH nonelectrolyteJ strong base

What should be taught…

• 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?

A. Mg(OH)2

B. NH3

C. NaOHD. 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?

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

F strong electrolyteG weak acidH nonelectrolyteJ strong base

This question could be adapted to address strong vs weak acids/bases.

Solutions

Education

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