Dilution

In segment D, the teacher and students discuss the results from the molarity lab and how to express concentrations using mass percent or molarity. The students learn how to work a dilution problem and create a plan for a lab during which they will perform a dilution to reach a specific molarity.

In segment D, the teacher and students discuss the results from the molarity lab and how to express concentrations using mass percent or molarity. The students learn how to work a dilution problem and create a plan for a lab during which they will perform a dilution to reach a specific molarity.

Premiere Date: August 7, 2016 | Runtime: 00:06:05

## Toolkit

Dilution Lab Instructions
Unit 7D Note Taking Guide & Segment Questions

## Crosscutting Concepts

Scale, Proportion, and Quantity

In considering phenomena, it is critical to recognize what is relevant at different measures of size, time, and energy and to recognize how changes in scale, proportion, or quantity affect a system’s structure or performance.

## Science & Engineering Practices

Constructing Explanations and Designing Solutions

The goal of science is the construction of theories that provide explanatory accounts of the world. A theory becomes accepted when it has multiple lines of empirical evidence and greater explanatory power of phenomena than previous theories.”(NRC Framework, 2012, p. 52)

Planning and Carrying Out Investigations

Students should have opportunities to plan and carry out several different kinds of investigations during their K-12 years. At all levels, they should engage in investigations that range from those structured by the teacher—in order to expose an issue or question that they would be unlikely to explore on their own (e.g., measuring specific properties of materials)— to those that emerge from students’ own questions. (NRC Framework, 2012, p. 61)

Using Mathematics and Computational Thinking

Although there are differences in how mathematics and computational thinking are applied in science and in engineering, mathematics often brings these two fields together by enabling engineers to apply the mathematical form of scientific theories and by enabling scientists to use powerful information technologies designed by engineers. Both kinds of professionals can thereby accomplish investigations and analyses and build complex models, which might otherwise be out of the question. (NRC Framework, 2012, p. 65)

## Vocabulary

acid - substances that ionize in solutions to form H^+ ions.

amphoteric - a substance that can be an acid or a base.

Arrhenius Model - in aqueous solutions, acids form hydrogen ions (H^+).

base - substances that ionize in solutions and form OH^- ions.

binary acids - acids that do not contain oxygen in their chemical formula.

boiling point elevation - occurs when the boiling point of a solution is higher than the boiling point of the pure solvent alone.

Bronsted-Lowry Model - this model states that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base.

colligative properties - properties of the solution that are different than those of a pure solvent by itself.

dilution - the process of adding more solvent to a solution.

electrolysis - the decomposition of water.

freezing point depression - a colligative property that describes how the freezing point of a solution is lowered compared to the freezing point of the pure solvent.

heterogeneous mixture - a combination of two or more substances in which the original substances are separated into physically distinct regions with differing properties.

homogeneous mixture - a combination of two or more substances that have uniform composition and chemical properties throughout; also known as a solution.

insoluble - a solid, liquid, or gas that will not dissolve in a particular solvent.

Lewis Model - bases donate pairs of electrons and acids accept pairs of electrons.

mass percent - a way of expressing how concentrated a solution is; is equal to the mass of the solute in a solution divided by the total mass of the solution and multiplying by 100.

mixture - a combination of two or more pure substances in which each pure substance retains its individual chemical properties.

molality - a ratio of moles of solute to the mass of the solvent in kilograms.

molarity - a ratio of moles of solute to the volume of the solution in liters.

oxyacids - acids that contain oxygen in their chemical formula.

pure substance - a material that has a constant composition and has consistent properties throughout the sample.

saturated solution - a solution in which the maximum amount of solute has been dissolved in a given amount of solvent at a particular temperature.

saturation point - the point at which no more solute can be dissolved in the solution at that particular temperature.

solubility - the maximum amount of a substance that can be dissolved in a given quantity of solvent at a given temperature to produce a saturated solution.

solute - the substance that is being dissolved in a solution.

solution - a liquid mixture in which the solute is uniformly distributed within the solvent.

solvent - the substance that is present in a greater amount in a solution.

supersaturated solution - a solution that is holding more dissolved solute than what it normally would hold at that temperature.

## Georgia Standards of Excellence

SC6Obtain, evaluate, and communicate information about the properties that describe solutions and the nature of acids and bases.

SC6.cUse mathematics and computational thinking to evaluate commercial products in terms of their concentrations (i.e., molarity and percent by mass).

SC6.dCommunicate scientific and technical information on how to prepare and properly label solutions of specified molar concentration.

SPS6Obtain, evaluate, and communicate information to explain the properties of solutions.

SPS6.aDevelop and use models to explain the properties (solute/solvent, conductivity, and concentration) of solutions.

SPS6.bPlan and carry out investigations to determine how temperature, surface area, and agitation affect the rate a solute dissolves in a specific solvent.

SPS6.cAnalyze and interpret data from a solubility curve to determine the effect of temperature on solubility.

## Request Teacher Toolkit

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