Chemical Reactions

Chemical Reactions 13: Another Approach to Recovering Copper

Students close the unit by applying what they have learned in previous activities to conduct a final investigation to figure out which precipitation reaction works best to remove copper from wastewater. Students analyze and interpret their data from this activity and the previous activity to develop their evidence-based argument for the best choice of reactions.

Chemical Reactions 12: Recovering Copper

Students investigate the use of reactions with three metals for reducing copper waste and reclaiming copper from the used copper etching solution produced in the first activity of the unit. Students use data from their investigation and text sources to develop an evidence-based argument for which metal is the best choice for recovering copper from the waste solution.

Chemical Reactions 11: Refining the Design

Students use the thermal energy release from combining iron, calcium chloride, and water to design a hand warmer. Students redesign, construct, test, and evaluate their hand warmer designs from the “Developing a Prototype” activity. Students must meet a new criterion as well—they must consider how to control the start of the chemical reaction in their design modifications.

Chemical Reactions 10: Developing a Prototype

Students undertake a design challenge to construct and test a hand warmer device that uses the thermal energy released from an iron exothermic reaction. Students investigated the exothermic reaction of iron, calcium chloride and water in the previous activity. When testing their designs, students analyze their results and brainstorm ideas for further modification.

Chemical Reactions 9: Thermal Energy and Reactions

Students explore chemical reactions that absorb or release thermal energy. Through classroom discussion, students learn more about the crosscutting concept that energy and matter are conserved but can transfer within a system between reactants, products, and the environment. They are also learn how the absorption or release of energy is caused by the rearrangement of atoms during a reaction. Some rearrangements require energy; others release it. Students set up two chemical reactions, measuring the temperature of the reactants and products. They use their measurements to identify which reaction releases and which absorbs energy.

Chemical Reactions 8: Chemical Batteries

Students investigate how chemical energy can be transformed via a chemical process into electrical energy. Students build a chemical battery that transforms chemical energy into electrical energy, which in turn powers a motor. After building an initial prototype battery, students are given a set of criteria and constraints and asked to design a chemical battery that spins faster than the initial prototype for at least 5 min. Students brainstorm, build, test, and evaluate their prototypes.

Chemical Reactions 7: Explaining Conservation of Mass

Students use a combination of molecular modeling and mathematical computation to describe the atomic/molecular basis for mass conservation in chemical reactions. They learn about the law of conservation of mass and the relevance of this law to various natural phenomena. They then tie this idea to the concept that the copper from the “Producing Circuit Boards” activity has not gone away; it is just in a different form.

Chemical Reactions 6: Comparing the Masses of Reactants and Products

Students explore the law of conservation of mass. After watching a demonstration of a reaction between Copper Chloride and Ammonia, they conduct their own precipitation reaction between Calcium Chloride and Sodium Carbonate and measure the total mass before and after the reaction. Future activities will build on this concept as students are asked to think about the implications of conservation of atoms and mass in their investigations of chemical methods of waste treatment.

Chemical Reactions 5: Chemical or Physical Change?

Student groups consider six scenarios that describe changes in matter. They apply evidence and logical reasoning to develop arguments about whether each scenario describes a physical change or a chemical reaction. They also analyze and interpret information on the observable properties of substances before and after a change to determine whether the change is a physical change or a chemical reaction. The changes considered include examples from earth, life, and physical sciences.

Chemical Reactions 4: Chemical Reactions at the Molecular Scale

Students use molecular models to explore the kinds and numbers of each kind of atom, as well as the arrangements of atoms, in the reactants and products of several chemical reactions. The patterns they observe demonstrate the concept of conservation of atoms in chemical reactions, as well as the relationship between changes at the atomic/molecular scale and changes in the observable properties of substances.

Chemical Reactions 3: Physical Changes and Chemical Reactions

Students read about observable (macroscopic) and atomic/molecular-level patterns of changes in physical and chemical properties and how they can be signs of chemical reactions. They also read about how to use logical reasoning to avoid mistaking physical changes for chemical changes. They integrate ideas in the reading with their observations of chemical changes in the previous investigation, and analyze and interpret several examples to determine whether a change is physical or chemical.

Chemical Reactions 2: Evidence of Chemical Change

The class reviews the safety guidelines for working with chemicals in the science classroom. They investigate five chemical changes. For each one, they identify the signs of chemical change and the elements present before and after the reactions. Students discover that in a chemical change, new substances form that have different properties from the starting substances. Students are introduced to the idea that the elements in the substances at the beginning and end of the reaction are the same, but they have rearranged into new chemical combinations.

Chemical Reactions 1: Producing Circuit Boards

After a brief introduction to the function of a circuit board in a computer and other electronic devices, students mask a design on a circuit board with permanent marker and etch it with an acidic copper-etching solution. On Day 2, after testing their circuits with a battery and light bulb, they will then read about the etching process and consider the copper-containing waste it produces. How to best handle the waste without harming the environment will be an issue student investigate throughout the unit.