Beacon Lesson Plan Library

What's the Reaction?

Lisa McElfresh
Santa Rosa District Schools

Description

This activity provides students with an opportunity to combine substances and compare their reactivity. The students find that observable changes take place in the color, behavior, or state of substances when a chemical change takes place.

Objectives

The student knows that materials made by chemically combining two or more substances have properties that differ from the original materials.

Materials

For Teacher Demonstration:
-One-gallon Ziploc bag
-200ml vinegar
-Rubberband
-1/2 cup baking soda
-Candle
-Lighter or match

For Each Student Group:
-1/2 cup baking soda
-400ml vinegar
-One teaspoon
-Two 500ml water bottles (for water and vinegar)
-Two paper cups
-400ml water
-Two balloons
-Two paper towels
-Two pennies
-Student Worksheet (See Associated File) for each student

Preparations

1. Prepare a Ziploc bag with about 200ml of vinegar at the bottom. Use a rubber band to cinch it in the middle. Above the rubber band place about ˝ cup of baking soda. Seal the bag.
2. Have a table set up in front of the room with a candle, lighter or match, and the prepared bag. This part of the lesson is for demonstration only. Remind students that fire is dangerous and this should only be done under adult supervision.
3. Divide class into groups of four. Have the materials ready for group use. Student materials for each group are: two water bottles, one with 200ml vinegar and one with 200ml of water; two balloons; two pennies; two paper cups, one filled with 200ml of water and the other filled with 200ml of vinegar; one teaspoon; 1/2 cup of baking soda; two paper towels; and a Student Worksheet for each student. (See Associated File)

Procedures

1. Light a candle and ask the students if they think that you can blow out the candle by just unzipping the top of the bag. Unzip the bag and hold near the candle. (The candle will remain lit.)

2. Zip the bag closed and gently cut the rubber band (without cutting the bag), which allows the vinegar to mix with the baking soda (creating carbon dioxide gas). Unzip the bag and hold the opening near the candle flame…it should go out.

3. Ask the students what they think happened. Write the questions and any hypotheses that are formulated on the board.

4. Hand out the Student Worksheets (See Associated File) and have students write descriptions of the baking soda, vinegar, water, and penny. Remind them of some ways to describe physical properties of substances such as color, texture, smell, shape, state (solid, liquid, gas).

5. Next, have the students put the two pennies in two separate cups: one filled with 200ml of water and one filled with 200ml of vinegar. Have them set this aside to examine again at the end of the activity.

6. Have students put three teaspoons of baking soda into a 500ml water bottle filled with 200ml of water. Their partner needs to be ready to put a balloon over the top of the opening of the bottle when finished. Have students observe and write down any changes that take place.

7. Have students repeat step six, except this time they will put three teaspoons of baking soda into a bottle with 200ml of vinegar.

8. After the observations have been recorded on the worksheet, have students examine the pennies. Have the students record any changes that have taken place in the pennies on their worksheets.

9. Ask students if they can tell why there is a difference between the way the penny and baking soda reacted in the water and in the vinegar.

10. Ask students if they can tell why there is a difference between what happened to each balloon.

11. Have them write their conclusions on the worksheet and discuss them with the whole class. What was the common denominator in each reaction? (the vinegar) What occurred to cause such drastic changes? Lead students to understand that sometimes two or more substances form chemical bonds and a new substance can be made that has different properties from the original substances. Have students reflect back to the demonstration. What were some changes in the substances’ properties? (a solid and a liquid turned into a gas, the new substance could extinguish a fire)

12. Collect Student Worksheets and assess for responses that reflect student understanding.

Assessments

Formative Assessment:
Observe student interaction in group work.

Summative Assessment:
Students write accurate descriptions of physical properties of substances on Student Worksheet (See Associated File) under correct headings. Students write conclusions on Student Worksheet after performing activity.

Web Links

This is a good site to visit after the lesson because it reinforces the concepts learned. Go to Brainpop, then choose Science Movies, then choose Compounds and Mixtures.
Brainpop

Attached Files

This file contains the Student Worksheet.     File Extension: pdf

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