Page 1 of 3 CC@WCCUSD 08/30/13 Grade Level/Course: Grade 8 Physical Science Lesson/Unit Plan Name: Evidence of Chemical Reactions Rationale/Lesson Abstract: Brief lab activity mixes three chemicals to observe evidence of chemical reaction, including color change, production of heat, loss of heat, and production of gas bubbles. Timeframe: 1 class period Standard(s): Reactions 5. Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept: a. Students know reactant atoms and molecules interact to form products with different chemical properties. c. Students know chemical reactions usually liberate heat or absorb heat.
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Page 1 of 3 CC@WCCUSD 08/30/13
Grade Level/Course: Grade 8 Physical Science Lesson/Unit Plan Name: Evidence of Chemical Reactions Rationale/Lesson Abstract: Brief lab activity mixes three chemicals to observe evidence of chemical reaction, including color change, production of heat, loss of heat, and production of gas bubbles. Timeframe: 1 class period Standard(s): Reactions 5. Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept: a. Students know reactant atoms and molecules interact to form products with different chemical properties. c. Students know chemical reactions usually liberate heat or absorb heat.
Page 2 of 3 CC@WCCUSD 08/30/13
Instructional Resources/Materials: Optional: Prentice Hall 2008 Physical Science textbook p. 218-‐221 or similar textbook resource Lab materials:
• Phenol Red (diluted is okay. Available through science supply vendors or some pool supply stores)
• Calcium Chloride (Also available through science supply vendors or some pool supply stores)
• Sodium Bicarbonate (baking soda) • Sandwich size Ziploc bags • Small containers, such as condiment cups, for phenol red
For each group/station:
• One sandwich size Ziploc bag • Small container for phenol red,
such as a condiment cup • (containers for other substances
are suggested, but optional) • ≈ 5 mL phenol red (diluted is okay) • ≈ 8 g calcium chloride • ≈ 12 g sodium bicarbonate
Activity/Lesson:
• Students in group should make observations of each of three substances present before mixing: phenol red, baking soda, CaCl2.
• To combine chemicals: • Pour both solids into Ziploc bag. (Students may be given specific instructions to keep them in separate corners of bag, or mixed together, or no detailed instructions—instructor’s choice).
• Container of phenol red is placed UPRIGHT in bag. DO NOT POUR/MIX PHENOL RED YET!
• Squeeze air out of the bag, as much as possible, then make sure the bag is completely sealed.
• Once the bag is sealed, tip over the cup of phenol red, allowing chemicals to mix. • Record observations. (Students should see notice some or all: loss of heat, production
of heat, color change, gas bubbles produced, etc.) • Dispose of Ziploc bag with chemicals.
Page 3 of 3 CC@WCCUSD 08/30/13
Activity/Lesson continued: OPTIONAL: Students may be allowed to research further; allow them to come up with their own questions, such as…
• What happens if only two of the substances are combined? • What happens if water is added? • What happens if water replaces phenol red? • What happens if the ratios/amounts are changed?
Assessment: Sample questions for handout or lab write-‐up: What is the difference between a physical change and a chemical reaction?
What evidence did you see that there was a chemical reaction?
Think about the experiment that we just did. What adjustments could you make to it?
Make up your own experiment by completing the following sentence:
“I wonder what would happen if __________________________________________________”
If a reaction releases heat, it is (exothermic /endothermi ).
Chocolate melting in the sun is a (chemical /physical ) change.
Endothermic reactions have energy in the (reactants /products).
Atoms get rearranged in (chemical reactions /physical changes).
The products are on the (left /right ) side of a chemical reaction.
If chemicals in a reaction become cooler, the reaction is (exothermic /endothermic).
Conservation of matter says the number of (atoms /molecules) are the same on both sides.
A new substance with new properties comes from a (chemical /physical) change.
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