Unit 10

Chapter Overview

During this unit, students learn more about solutions and the unique chemical and biological properties of water.  They are introduced to the idea of concentration and how it is expressed in moles / liter.  Finally, they develop and use solubility rules for aqueous solutions and investigate factors that affect solubility and dissolution.

Main Ideas

1. A solution is a homogeneous mixture composed of a solvent and one or more solutes.

2. Water plays a unique role in chemical and biological systems due to its molecular structure.

3. There are several ways to describe aqueous solutions.

4. Solution concentrations can be expressed in mol / liter (M).

5. Water-solute interactions influence how much solute dissolves.

6. Rates of solute dissolution and solubility in water are influenced by external factors.

7. A solubility curve conveys information about how temperature affects the solubility of a solute.

8. There is a set of general rules that can be used to predict solubilities.

Misconceptions

• Students may think dissolving is the same as melting or “turning into water”.

• Students may not understand how to use dimensional analysis.

• Students may not understand significant figures.

• Students may not understand that there are gradations of solubility, from insoluble to highly soluble.

• Students may not understand that there is more than one way to describe the concentration of a solution.

• Students may not understand that gases and liquids, as well as solids, can be dissolved in water.

Vocabulary

• Non-Polar Molecule – a covalent compound in which electrons are equally shared between atoms (Ex. oxygen gas)

• Polar Molecule – a molecule where there is an uneven distribution of electrons, causing one part to more negative and one part to be more positive

• Intermolecular Forces – forces of attraction or repulsion that act between neighboring particles

• Hydrogen Bonding – a weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other

• Solubility – the extent to which a solute dissolves in a solvent

• Solution – a homogenous aqueous mixture

• Solvent - The component of a solution that is present in the greatest amount. It is the substance in which the solute is dissolved. Examples: The solvent for seawater is water.

• Solute – a substance dissolved in another substance

• Aqueous – a solution of a solute in water

• Aqueous Solution – a solution in which a solute is mixed in water (solvent)

• Molarity (M) – solution concentration expressed as the number of moles of solute dissolved in a liter of solution, mol / L

• Dissolution – dissolution of gases, liquids, or solids into a liquid or other solvent is a process by which these original states become solutes (dissolved components), forming a solution of the gas, liquid, or solid in the original solvent

• Dissociation – process in which ionic compounds separate or split into smaller particles (ions) when added to a solvent

• Deionization – removal of ions from a solution

• Conductor (electrolytes) – solutions with ions that conduct electricity

• Electrolytes - chemical compound that conducts electricity by changing into ions when melted or dissolved into a solution

• Nonelectrolytes – a substance that does not exist in an ionic form in aqueous solution

• Concentration – a measurement of the amount of solute that is dissolved in a given quantity of solvent.

• Diluted – make a solution thinner or weaker by adding water or another solvent to it

• Dilution - process of reducing the concentration of a solute in solution, usually simply by mixing with more solvent. Example: You can add water to concentrated orange juice to dilute it until it.

• Unsaturated Solution – a solution (with less solute than the saturated solution) that completely dissolves, leaving no remaining substances

• Saturated Solution – a solution with solute that dissolves until it is unable to dissolve anymore, leaving the undissolved substances at the bottom

• Supersaturated Solution – a solution (with more solute than the saturated solution) that contains more undissolved solute than the saturated solution

• Agitation – putting into motion by shaking or stirring, often to achieve mixing

• Surface Area – total area on the outside surface of a three-dimensional figure

• Surface Tension – a physical property equal to the amount of force per unit area necessary to expand the surface of a liquid

• Polarity – polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole 

• Precipitate – precipitate is an insoluble solid that emerges from a liquid solution

Notes

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