3. Where's the Evidence?

Objective: Observe Evidence of Chemical Reactions

Big Idea Application:
During chemical processes matter can change forms.

The overarching essential questions being considered:

What happens during a chemical reaction?

The essential questions being considered:
How can you tell if a chemical reaction has occurred, when two chemicals are mixed?

Approach/ Strategy being applied:

  1. Concept Maps
  2. Engagement, Exploration, Explanation, Elaboration, Evaluation- 5E Instructional Model
  3. Evaluation Tool from the Poison Project Article
  4. Structured Inquiry

Standard Addressed: 5a: Students know reactant atoms and molecules interact to form products with different chemical properties.

Materials:

  • Marshmallow 
  • Where's the Evidence Lab Activity Student Sheet (see attachment below)
  • 4 small plastic cups                   
  • birthday candles
  • 2 plastic spoons                   
  • sugar    
  • Tongs                           
  • clay
  • Lighter                           
  • sodium carbonate (powdered solid)
  • Graduated cylinder, 10ml               
  • Test tubes (2)
  • Aluminum foil, about 10-cm square           
  • Test tube rack
  • Dilute hydrochloric acid in a dropper bottle       
  • copper sulfate solution
  • Sodium carbonate solution

Anticipatory Set (Hook):

  1. Give the students a marshmallow.  
  2. Ask the questions:
    • How many different ways can you alter the marshmallow "physically" and still end up with a marshmallow?
    • List the ways you could alter the marshmallow "chemically" to create a new substance that is no longer the same as the original marshmallow?
  3. Make a chart of all the ideas on the board.  
  4. Explain that during the lab we will investigate evidence of new substances forming and chemical changes occurring.     

Lesson Plan:


Review terminology- physical change, chemical change

Where's the evidence lab activity

Part 1

  1. Put a pea-sized pile of sodium carbonate into a clean plastic cup.  Record the appearance of the sodium carbonate on the data table.
  2. Observe a dropper containing hydrochloric acid.  Record the appearance of the acid on the data table. CAUTION:  Hydrochloric acid can burn you or anything else it touches.  Wash spills with water.    
  3. Made a prediction about how you think the acid and the sodium carbonate will react when mixed.  Record your prediction on the data table.
  4. Add about 10 drops of hydrochloric acid to the sodium carbonate. Swirl to mix the contents of the cup.  Record your observations on the data table.

Part 2    

  1. Fold up the sides of the aluminum foil square to make a small tray.
  2. Use a plastic spoon to place a pea-sized pile of sugar onto the tray.
  3. Carefully describe the appearance of the sugar on your data table.
  4. Secure a small candle on your desktop in a lump of clay.  Carefully light the candle with a lighter, only after being instructed to do so by your teacher.  CAUTION: Tie back long hair and loose clothing.
  5. Predict what you think will happen, if you heat the sugar.  Record your prediction on the data table.
  6. Use tongs to hold the aluminum tray.  Heat the sugar slowly by moving the tray gently back and forth over the flame.  Make observations, while the sugar is heating.
  7. W