3. Where's the Evidence?
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 ...
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:
- Concept Maps
- Engagement, Exploration, Explanation, Elaboration, Evaluation- 5E Instructional Model
- Evaluation Tool from the Poison Project Article
- Structured Inquiry
Standard Addressed: 5a: Students know reactant atoms and molecules interact to form products with different chemical properties.
- Where's the Evidence Lab Activity Student Sheet (see attachment below)
- 4 small plastic cups
- birthday candles
- 2 plastic spoons
- 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):
- Give the students a marshmallow.
- 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?
- Make a chart of all the ideas on the board.
- Explain that during the lab we will investigate evidence of new substances forming and chemical changes occurring.
Review terminology- physical change, chemical change
Where's the evidence lab activity
- Put a pea-sized pile of sodium carbonate into a clean plastic cup. Record the appearance of the sodium carbonate on the data table.
- 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.
- Made a prediction about how you think the acid and the sodium carbonate will react when mixed. Record your prediction on the data table.
- 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.
- Fold up the sides of the aluminum foil square to make a small tray.
- Use a plastic spoon to place a pea-sized pile of sugar onto the tray.
- Carefully describe the appearance of the sugar on your data table.
- 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.
- Predict what you think will happen, if you heat the sugar. Record your prediction on the data table.
- 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.
- When you think there is no longer a chemical reaction occurring, blow out the candle.
- Allow the tray to cool for a few seconds and set it down on your desk.
- Record your observations of the material left in the tray.
- Put about 2ml of copper sulfate solution in one test tube. CAUTION: Copper sulfate is poisonous and can stain your skin and clothes. Do not touch it or get it in your mouth.
- Put an equal amount of sodium carbonate solution in another test tube.
- Record the appearance of both liquids on the data table.
- Write a prediction of what you think will happen, when the two solutions are mixed. Record your prediction on the data table.
- Combine the two solutions into one test tube and record your observations. Note- the reaction occurs quickly.
- CAUTION: Dispose of the solution, as directed by your teacher.
- Wash your hands and clean up, when you have finished working.
Complete the analysis and conclusion section of the lab.
Contribution to student understanding:
This lesson asks the students to describe, explain, and predict the outcomes of the experiments. Using this type of questioning will increase their "scientific literacy" and foster their understanding of the "nature of science." The "nature of science" states that all scientific knowledge is based, at least partially, on and/ or derived from observation of the natural world.