Science
Strand IV
Use Scientific Knowledge from the Physical Sciences in Real-World Contexts

 

Science/Strand IV
Content Standard 2
All students will investigate, describe, and analyze ways in which matter changes; describe how living things and human technology change matter and transform energy; explain how visible changes in matter are related to atoms and molecules; and how changes in matter are related to changes in energy. (Changes in Matter)

 

Science/Strand IV/Content Standard 2
High School

 

Science/Strand IV/Content Standard 2/High School
Benchmark 1
Explain chemical changes in terms of the breaking of bonds and the rearrangement of atoms to form new substances.

Benchmark Clarification

Bonds (attachments or connections) between atoms break, and the atoms move around and rearrange into new substance(s) with new bonds.

The substance(s) that undergo the change are called reactants, and the substances that are formed are called the products. The numbers and kinds of atoms present in the reactants are the same as in the products (only the arrangement has been changed).

Reaction rates can be increased by increasing temperature, surface area, and/or concentration.

Types of bonds (ionic and covalent) are not emphasized, because they are not considered critical to scientific literacy.

Students will:

  • Describe chemical changes as groups of atoms rearranging to form different substances

Key Concept / Real World Context / Instructional Example / Assessment Example / Resources

 

Science/Strand IV/Content Standard 2/High School/Benchmark 1
Key Concept

  • atom
  • molecule
  • ion
  • bond
  • reactant
  • product
  • conservation of mass

Specific chemical reactions:

  • burning paper or wood
  • rusting iron
  • formation of sugars during photosynthesis

Rate of reaction:

  • temperature
  • surface area
  • concentration

See Structure of the atom.(SCI.IV.1.HS.3).

 

Science/Strand IV/Content Standard 2/High School/Benchmark 1
Real World Context
Examples of chemical changes (SCI.IV.2.MS.2)

 

Science/Strand IV/Content Standard 2/High School/Benchmark 1
Instructional Example

Benchmark Question: How does matter change?

Focus Question: How does matter change in chemical changes?

After the teacher demonstrates, describes, and models a chemical change, students will perform a chemical change in small lab groups. The groups will model the chemical change using colored mini marshmallows and toothpicks. The following is a suggestion of an appropriate chemical change investigation for students:

The Rusting of Iron (Oxidation)

  1. Rinse a small marble-sized sample of steel wool (Fe) in a dish of dilute HCl (0.1M).
  2. Place the sample in the bottom of a test tube and invert the test tube. The steel wool should fit snugly enough into the tube so that it doesn’t fall out.
  3. Fill a small beaker (approx. 250 ml) with water to a depth of about two cm.
  4. Place the inverted test tube into the beaker with the water.
  5. Let this stand for an hour or overnight.
  6. Observe the water level and the steel wool. The water level in the tube should rise as a result of oxygen (O2) leaving the gaseous state and combining with iron (Fe) and forming the solid rust (Fe2O3).
  7. Discuss the following reaction that occurs:
         4Fe + 3O2 2Fe2O3
  8. Groups should use one color of marshmallow for iron, another for oxygen, and construct a model with toothpicks (for bonds) to represent the reaction.

Small groups will describe the chemical change in writing and will share this writing with other groups and classes.

Constructing: (SCI.I.1.HS.1), (SCI.I.1.HS.2), (SCI.I.1.HS.5).

Reflecting: (SCI.II.1.HS.1).

 

Science/Strand IV/Content Standard 2/High School/Benchmark 1
Assessment Example

Students will illustrate and explain the rearrangement of atoms in the formation of new substances in one or more of the following chemical changes:

NaOH + HCl NaCl + H2O

(Give students rubric before activity.)

Scoring Rubric

Criteria

Apprentice

Basic

Meets

Exceeds

Accuracy of illustration

Illustrates inaccurately the arrangement of atoms in reactants and products or provides no illustration.

Illustrates accurately the arrangement of atoms in products or reactants.

Illustrates accurately the arrangement of atoms in products and reactants.

Illustrates accurately the arrangement of atoms in products and reactants and shows the breaking and forming of bonds to form new substances.

Correctness of explanation

Explains incorrectly or fails to explain at all.

Explains in a vague and/or incomplete manner.

Explains and mentions breaking of bonds and rearrangement of atoms to form new bonds and new substances.

Explains and mentions breaking of bonds and rearrangement of atoms to form new bonds and new substances. Gives an additional explanation of a chemical change.

 

Science/Strand IV/Content Standard 2/High School/Benchmark 1
Resources

Webliography.
http://mtn.merit.edu/mcf/SCI.IV.2.HS.1.html

Atoms, molecules and chemical reactions.
http://step.sdsc.edu/projects95/ATOM.PROGRAM/Atoms.html

Chem 4 Kids”.
http://www.chem4kids.com/map.html

Chem Web Online Introduction to Chemistry.
http://library.advanced.org/10429/