Limiting Reactants

This segment explores limiting reactants as we watch the students perform a lab with s'mores.

The students perform a lab demonstrating a limiting reactant problem.

Premiere Date: July 11, 2016 | Runtime: 00:21:21

## Toolkit

Pipette Rocket Lab
S'mores Activity Sheet
Unit 6E Classroom Activity- Limiting Reactants 1
Unit 6E Classroom Activity- Limiting Reactants 2
Unit 6E Lab Investigation- Calculating the Theoretical Yield and Percent of Copper
Unit 6E Lab Investigation- Using Stoichiometry to Determine Theoretical Yield of a Reaction
Unit 6E Note Taking Guide & Segment Questions
Unit 6E Practice Problems 4- Limiting Reactants
Unit 6E Practice Problems 5- Percent Yield Calculations
Unit 6E Practice Problems 6- Limiting Reactants
Unit 6E Practice Problems 7- Percent Yield Calculations

## Crosscutting Concepts

System and System Models

Defining the system under study—specifying its boundaries and making explicit a model of that system—provides tools for understanding and testing ideas that are applicable throughout science and engineering.

Patterns

Observed patterns of forms and events guide organization and classification, and they prompt questions about relationships and the factors that influence them.

Energy and Matter

Flows, cycles, and conservation. Tracking fluxes of energy and matter into, out of, and within systems helps one understand the systems’ possibilities and limitations.

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.

Cause and Effect

Mechanism and explanation. Events have causes, sometimes simple, sometimes multifaceted. A major activity of science is investigating and explaining causal relationships and the mechanisms by which they are mediated. Such mechanisms can then be tested across given contexts and used to predict and explain events in new contexts.

## Science & Engineering Practices

Analyzing and Interpreting Data

Once collected, data must be presented in a form that can reveal any patterns and relationships and that allows results to be communicated to others. Because raw data as such have little meaning, a major practice of scientists is to organize and interpret data through tabulating, graphing, or statistical analysis. Such analysis can bring out the meaning of data—and their relevance—so that they may be used as evidence.
Engineers, too, make decisions based on evidence that a given design will work; they rarely rely on trial and error. Engineers often analyze a design by creating a model or prototype and collecting extensive data on how it performs, including under extreme conditions. Analysis of this kind of data not only informs design decisions and enables the prediction or assessment of performance but also helps define or clarify problems, determine economic feasibility, evaluate alternatives, and investigate failures. (NRC Framework, 2012, p. 61-62)

Students at any grade level should be able to ask questions of each other about the texts they read, the features of the phenomena they observe, and the conclusions they draw from their models or scientific investigations. For engineering, they should ask questions to define the problem to be solved and to elicit ideas that lead to the constraints and specifications for its solution. (NRC Framework 2012, p. 56)

Generating a Hypothesis and Developing a Model

Modeling can begin in the earliest grades, with students’ models progressing from concrete “pictures” and/or physical scale models (e.g., a toy car) to more abstract representations of relevant relationships in later grades, such as a diagram representing forces on a particular object in a system. (NRC Framework, 2012, p. 58)

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

atomic mass unit - equals 1/12 the mass of a carbon atom.

Avagadro's number - the number of atoms in a mole, equal to 6.02x10^23 atoms.

conversion factor - a ratio expressed as a fraction that equals one.

dimensional analysis - the sequential application of conversion factors expressed as fractions and arranged so that any dimensional unit can be cancelled out until the desired set of dimensional units is obtained.

empirical formula - the simplest formula of a compound expressed as the smallest possible ratio of the elements.

equivalence statement - a statement that shows the quantities and units that are equal to each other.

excess reactant - the reactant in a chemical reaction that remains when a reaction stops once the limiting reactant is completely consumed.

limiting reactant - the reactant in a chemical reaction that limits the amount of product formed.

molar mass - the mass, in grams, of a mole of a substance.

molar volume - the volume of one mole of any gas at standard temperature and pressure.

mole - The SI unit that measures the amount of matter a substance has; one mole is equal to 6.022x10^23 representative particles, also known as Avagadro's number.

mole ratio - the ratio of moles of one substance to the moles of another substance in a balanced equation.

molecular formula - a formula which states the exact number and type of each atom present in a molecule of a substance.

percent composition - the percentage by mass of each element in a compound.

percent yield - the ratio of the actual yield to the theoretical yield of a material.

stoichiometry - the calculation of the quantities of reactants and products involved in a chemical reaction.

theoretical yield - the amount of product formed from the complete conversion of a limiting reactant in a chemical reaction.

## Georgia Standards of Excellence

SC3Obtain, evaluate, and communicate information about how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.

SC3.aUse mathematics and computational thinking to balance chemical reactions (i.e. synthesis, decomposition, single replacement, double replacement, and combustion) and construct an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

SC3.bPlan and carry out investigations to determine that a new chemical has formed by identifying indicators of a chemical reaction (specifically precipitate formation, gas evolution, color change, water production, and changes in energy to the system should be investigated).

SC3.cUse mathematics and computational thinking to apply concepts of the mole and Avogadro’s number to conceptualize and calculate:

• percent composition

• empirical/molecular formulas

• mass, moles, and molecules relationships

• molar volumes of gases

(Clarification statement for elements c and d: Emphasis is on use of mole ratios to compare quantities of reactants or products and on assessing students’ use of mathematical thinking and is not on memorization and rote application of problem- solving techniques.)

SC3.dUse mathematics and computational thinking to identify and solve different types of reaction stoichiometry problems (i.e., mass to moles, mass to mass, moles to moles, and percent yield) using significant figures. (Clarification statement for elements c and d: Emphasis is on use of mole ratios to compare quantities of reactants or products and on assessing students’ use of mathematical thinking and is not on memorization and rote application of problem- solving techniques.)

SC3.ePlan and carry out an investigation to demonstrate the conceptual principle of limiting reactants.

## Request Teacher Toolkit

The Chemistry Matters teacher toolkit provides instructions and answer keys for labs, experiments, and assignments for all 12 units of study. GPB offers the teacher toolkit at no cost to Georgia educators. Complete and submit this form to request the teacher toolkit. You only need to submit this form one time to get materials for all 12 units of study.