Tuesday, January 7, 2014

MS - PS1.B (A) - Characteristics of a Chemical Reaction - FINAL (CLF - 1/10/2014)

DCI: PS1.B (A) Substances that react chemically in characteristic ways.  In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.
PE: MS-PS1-2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
PE: MS-PS1-3 Gather and make sense of information to describe that synthetic materials come from natural resources and impact society.

PE: MS-PS1-5 Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

[Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.] [Assessment boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.]

[Clarification Statement: Emphasis is on natural resources that undergo a chemical process to form the synthetic material. Examples of new materials could include new medicine, foods, and alternative fuels.] [Assessment Boundary: Assessment is limited to qualitative information.]

[Clarification Statement: Emphasis is on law of conservation of matter and on physical models or drawings, including digital forms, that represent atoms.] [Assessment Boundary: Assessment does not include the use of atomic masses, balancing symbolic equations, or intermolecular forces.]

Again, this module only focuses on one part of a larger standard.  For this batch, we need to concentrate on the following content ideas: 

-substances can react chemically 
- during chemical reactions, the atoms of the original substance are rearranged into different molecules
- the molecules formed as a result of a chemical process have different properties from the original substances

We can ask general questions about what happens to atoms during a chemical reaction.  Also, we can go ahead and pull in the PEs (only so far as they relate to rearrangement of atoms, or different properties of products vs. reactants).  

Looking at the third PE listed, it becomes clear that we can include conservation of mass questions.  Also - it stands to reason that students would need to be able to count the number of atoms before a reaction and compare it to those after a reaction to see if it follows the law of conservation of mass.  We will not have students balance chemical equations, but it is likely ok to have them count the atoms. 

Possible Question Starters: 
"The law of conservation of mass relates to atoms in a chemical reaction in which of the following ways?"
correct answer - the number of atoms present before a chemical reaction must equal the number of atoms present after a chemical reaction 
incorrect answer - atoms are continually generated as matter undergoes changes through the process of chemical reactions 

"The chemical equation represents the reaction between a solid sample of zinc metal and liquid hydrochloric acid. 
Zn + 2HCl à ZnCl2 + H2
Which of the following provides the the best evidence that this reaction follows the law of conservation of mass?"
correct answer - there are the same number and type of atom on both sides of the equation 
incorrect answer - all of the elements that were present before the reaction are present after the reaction 

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