The purpose is to develop students’ understanding of change in the rate of chemical reactions due to an increase in temperature
Properties of objects and materials, chemical reactions, reaction rates
In general for every 10°C increase in temperature, the reaction rate doubles up until the point at which decomposition of the reactants occurs.
3 plastic containers for water
Warm tap water, room temperature water, and ice water
Show the students the lightsticks. Activate one lightstick. Ask the students if they have ever heard placing a lightstick in a freezer will extend the life of the lightstick. Ask the students to predict which lightstick will be brighter, one in hot water, one in room temperature water, or one in ice water.
Place three water containers (warm, room temperature, and ice water) at each station. Ask the students to keep the water in the containers as much as possible. The materials manager will come to the front when called by the teacher to obtain a thermometer and three lightsticks.
Each group of students will activate the lightsticks (at the same time as much as possible) and place one lightstick in each container of water. The recorder will write the results on the group’s data sheet. The reporter will write the results on the board when requested by the teacher.
The leader will make sure the station is clean and the materials manager will return the thermometer and lightsticks to the teacher when requested. The leader will make sure the names of all group members is on the data sheet and the data sheet is turned in as specified by the teacher.
Share class data. The students should find the lightstick in the warm water was the brightest and the lightstick in the ice water is very dim.
Concept taught: In general, the rate of a chemical reaction increases as the temperature increases. More of the chemicals in the lightstick react at the higher temperature and the lightstick is brighter. However, the lightstick will not last as long because the chemicals are used up at a faster rate. Placing the lightstick in the freezer will prolong the life of the lightstick because the rate of the chemical reaction is slowed due to a lower temperature.
Ask for volunteers to take home a lightstick. Some of the students should place the lightsticks in warm water (or outside in the summer), at room temperature, and in the freezer.
Time how long the lightsticks last at each temperature. Prepare a class bar chart with the results.
Assess participation and check for understanding that chemical reactions will generally speed up when heated.
Summer Time Fun:
Parents and children can enjoy this activity together for summer time science fun.
Discuss how fireflies produce light from the same chemical reaction as the materials found in light sticks.
Discuss how the use of pesticides and lights from homes and businesses have reduced the number of fireflies. (Note: Fireflies are actually a beetle, not a fly). The following website has more information: http://www.ecomii.com/blogs/building/2009/07/13/keepingthe-firefly-flicker/
Fireflies are used by scientists to study how the changes in cells caused by diseases like muscular dystrophy . See the following for more information: http://animals.nationalgeographic.com/animals/bugs/firefly.html
Visit the following website for more information on fireflies and other animals with bioluminescence: https://www.nationalgeographic.com/animals/invertebrates/group/fireflies/