ZERO-IN

Italicized font represents information to be shared orally or physically completed with the students at this time.

Non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that we live in a world of solutions. The atmosphere is a gaseous solution. The oceans are saline solutions and, even our bodies, are largely aqueous solutions. To understand the world in which we live and the organisms that inhabit it, we need to know about solutions.

BRANCH OUT

Remind students that hydrogeologists study the major processes affecting solutes in rivers and streams. These solutes may be pollutants, such as pesticides, or naturally occurring substances such as dissolved gases. Studying the effects of solutes is important because pollutants may pose a threat to public health and the aquatic organisms that inhabit the rivers and streams.

GET FOCUSED

Inform students that the Investigation is designed to help them to answer the following Focus Questions:

• What affects the solubility of a solute? The unique combination of elements that make up each compound results in the differing solubility of each compound.

• Is there a relationship between the concentration of a solution and the saturation point of a solute? Yes. Solutes are able to dissolve and form solutions only up to concentration that corresponds to their specific saturation points. Any amount of solute greater than the saturation point will not dissolve.

Note: These questions are located in students’ SDRs at the beginning and end of the Investigation.

Note: These are succinct responses to the Focus Questions and are placed here for your reference at this time. Fully developed responses to the Focus Questions can be found on the PostLab page.

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

• A solution is a mixture of two or more substances, usually, a solid called the solute and a liquid called the solvent.
• The substance present in the smallest amount is the solute.
• The substance present in the greatest amount is the solvent. 
• In a solution, the solute is completely dissolved or mixed with the solvent so that none of the solute is visible. When a solute can dissolve in a solvent, it is soluble in the solvent.
• The amount of a solute dissolved in a solvent is termed its concentration.
• The concentration of a solute can be written as the number of grams of solute that are dissolved in a certain number of milliliters of solvent, usually 100 milliliters.
• The solute is completely dissolved when every solute particle is surrounded by many solvent particles.
• Sometimes the solvent particles can only surround some of the solute particles. The solute particles surrounded by the solvent particles are part of the solution but those that cannot be surrounded are not.
• Any solute that cannot dissolve is usually visible as solid solute resting at the bottom of the solution.
• How well a solute dissolves in a solvent is called its solubility.

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

• solution
• solute
• solvent
• dissolve
• soluble
• concentration
• solubility
• saturation point

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

• Direct students to complete the Recall section in their SDRs. Student answers may vary.

• • What is solubility?
  • Do different solutes have the same solubility or a different solubility?
  • How can you tell if a solid is soluble?
  • How can you tell if a solid is not soluble?

• Explain to students that they will be using several different chemical compounds in Lab. Explain to students that the compounds are substances that can be found in many household kitchens.
• Explain to students that every substance, whether found in kitchens or science laboratories is a chemical.
• Write the following chemical formulas and substance names on the board as a way of introducing students to the chemical formulas of the different chemical compounds that will be used as solutes:

• • NaHCO3 Baking Soda
  • NaCl Salt
  • C12H22O11 Sugar.

• Explain to students that each compound is composed of different atoms that are represented by the chemical formula they see. Each formula is different because each chemical is different.
• Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
• After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.