Summary

In this lesson, students complete a series of simple lab experiments to better understand chemical reactions as well as differentiate between chemical change and physical change. Students will also be introduced to the pH scale, and have the opportunity to understand how chemical reactions can be used in real-world scenarios.

Grade Level

Elementary School

Objectives

By the end of this lesson, students should be able to

• Analyze the effect of changing a variable in an experiment.
• Differentiate between chemical and physical change.
• Explain the difference between an endothermic and an exothermic reaction.
• Identify carbon dioxide through observations of a chemical reaction.
• Examine data collected during an experiment and draw a conclusion.
• Use an indicator to determine the pH of a substance.

Chemistry Topics

This lesson supports students’ understanding of

• Chemical Reactions
• Chemical Change
• Physical Change
• Observations
• Acids & Bases
• pH scale
• Indicators

Time

Teacher Preparation:

• Lab 1: 15 minutes
• Lab 2: 10 minutes
• Lab 3: 10 minutes
• Lab 4: 30 minutes (including shopping time)

Lesson:

• Lab 1: 30 minutes
• Lab 2: 30 minutes
• Lab 3: 30 minutes
• Lab 4: 30-40 minutes

Materials

Lab 1:

• 100mL beaker
• 50mL graduated cylinder
• ½ teaspoon measuring spoon
• Baking soda

Lab 2:

• 100mL beaker
• 50mL graduated cylinder
• ½ teaspoon measuring spoon
• Baking soda
• Thermometer

Lab 3:

• Dropper
• Small plastic cups
• Vinegar
• Rock samples (suggestions: limestone, granite, quartz, feldspar, calcite, the more variety the better)

Lab 4:

• Baking Soda
• Teaspoons
• Graduated Cylinder
• Water
• pH paper (optional)
• Sour candies (suggestions: Sweetarts, X-treme Airheads, Starburst, Sour Skittles, WarHeads)

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Food in the lab should be considered a chemical not for consumption.

Teacher Notes

• This lesson is intended to expand upon the somewhat common practice of combining vinegar and baking soda to demonstrate a simple chemical reaction.
• I teach this as a unit to my second graders. They enjoy the traditional wow factor associated with mixing baking soda and vinegar, but then have the opportunity to learn more when this concept is further applied to other topics like geology and candy.
• This unit could be used with any grade K-5 with minor adjustments. It would require some pre-planning and slight adjustments to make it align best with the abilities of higher or lower grade levels.
• I do this unit in second grade because they are studying physical and chemical changes in their self-contained science classrooms. I make sure my students have a grasp on this concept prior to this section.
• When purchasing candy for Lab 4, I usually buy at the local dollar store which tends to have a larger selection of sour candies than the grocery store.

Overview of Lessons (there is a student directions/handout included for each day):

• Lab 1: Students use graduated cylinders and measuring spoons to measure given amounts of each reactant.They complete the reaction several times, changing the amount of baking soda each time. For each reaction, student must start with a new sample of vinegar. Students can complete this individually or in small groups.
• Lab 2: The baking soda and vinegar reaction is repeated, but this time, students measure the temperature during the chemical change. The children are always shocked that the temperature decreases during the reaction. My goal with second graders in this lesson is twofold. First, it’s to show them that temperature changes in a chemical reaction and secondly to get them thinking about energy transformation. Older children could easily use this experiment to learn about the law of the Conservation of Energy.
• Lab 3: On day three of this unit, I give the students samples of different type of rocks, including limestones and droppers full of vinegar. Students are asked to separate the rocks based on whether they react/create carbon dioxide (fizz) with the vinegar or not. We then examine the characteristics of the rocks that reacted and they all look and feel the same. These are limestone rocks. Limestone reacts with vinegar due to the calcium carbonate in limestone, which is a base. Although I teach this lesson to my second graders, I revisit it with my fourth graders when we study geology and sinkholes.
• Lab 4: For our final lesson, we learn about the meaning of sour by partially dissolving a variety of sour candies in water, and adding a fixed amount of baking soda to the water mixture. This is where I finally introduce the pH scale. My older students use pH indicators to actually test the pH. My younger students observe the carbon dioxide produced from the reaction (fizz) and put the cups of dissolved candy in order from the most fizzy to the least fizzy. The amount of fizziness shows how acidic a candy is or isn’t. The more sour the candy is, the more acid that is present in the candy. You can show the children on a pH scale where the candies they tested fall. A final link is that the more acidic a candy is, the more damaging it is to their teeth. Parents absolutely love this connection! Please note that students should never eat materials in the lab!
• Find out more about this lesson in the May 2018 issue of Chemistry Solutions.