Endothermic and Exothermic Processes: An inquiry-based investigation

This activity is designed to challenge student understanding of endo- and exo- thermic processes.
Students will make and record accurate observations.
Students will differentiate between endo- and exo- thermic processes.
Students will analyze and synthesize their ideas in order to make a prediction.
Vocabulary terms: endothermic, exothermic, system, surroundings

This activity could be used in 9th grade physical science to introduce endo- and exo-thermic processes. It could also be used to reinforce these concepts in high school chemistry while introducing entropy, enthalpy, and spontaneous reactions.
Time: one class period
Materials: common items

Materials needed:
thermometer
Steel wool (brillo pads)
vinegar
100mL beaker
pre-packaged alcohol wipes
rubber bands
hair dryer (for teacher)

Part I:
1. Pour about 50 mL of vinegar into beaker and place thermometer into beaker. Initial temp: _________
2. Add the steel wool to the vinegar and take temperature readings at: 1 minute ________ 2 minutes _________ 3 minutes ____________
What did you observe?
Was heat absorbed or released by the system? Surroundings?
Explain what is happening. Is this endo- or exo- thermic?
Here is what you observed: steel wool + vinegar ----> iron oxide
Write in where "heat" fits into this equation.

Part II:
1. Take alcohol wipes and open package.
2. Rub the alcohol wipe on your forearm.
What do you observe?
Is heat absorbed or released by the system? Surroundings?
Explain what is happening. Is this endo- or exo- thermic?
This is what you observed: isopropyl alcohol (liquid) ----> isopropyl alcohol (gas)
Write in where "heat" fits into this equation.

Part III:
1. Take a rubber band between two fingers and rapidly stretch it outwards.
2. Quickly hold it to your forehead or cheek.
What do you observe?
3. Stretch it again and then let it contract. Quickly hold it to your forehead or cheek.
What do you observe?
Explain what is happening. Is this endo- or exo- thermic?
Here is what you observed: relaxed rubber band -----> stretched rubber band
Write where "heat" fits into this equation.

Challenge: Based on all your observations, predict the outcome of heating the rubber band with a hair dryer. Will it stretch out, contract, or have no effect?

For teacher: Hang a rubber band on a ring stand with small weight attached. Make the rubber band taunt but not "stretched out". Have students make predictions and make groups of "stretch", "contract", "no effect".

After demo, have students answer the following on their own.
1. Was your prediction correct? Explain why or why not.

Students may seem to have a clear understanding of these two processes after Parts I and II. After stretching and contracting the rubber band the students may have difficulty with this being endothermic. The contraction of the rubber band takes heat in (endothermic) but many students will still predict that the rubber band will stretch. After the demo, discuss these two processes along with how our preconceived ideas can lead us to the wrong predictions even when we have scientific data to explain otherwise.

Students will make and record their observations in their lab books. Students will also hand in their final challenge answer on an individual basis to assess learning. Students will also be assessed on their group participation and discussion that follow the lab activity.

9.1.1.1.1 knowing about the natural world
9.1.1.2.2 evaluate, examine, and compare evidence
9.1.1.2.3 identify critical assumptions
9.2.1.2.4 relate exothermic and endothermic processes