Warm up or cool down
Objective: Experimenting with exothermic and endothermic processes
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Laboratory materials
Beakers
Thermometers
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Reagents
Ammonium chloride (NH4Cl)
Sodium thiosulfate (Na2S2O3)
Sodium hydroxide (NaOH)
Calcium chloride (CaCl2)
Urea (CO(NH2)2)
Water
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Safety
Don't forget the gloves, lab coat, and safety goggles!!!
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Questions
What processes are exothermic? And which ones are endothermic?
Do you think all these processes are chemical reactions?
Procedure
- Add 30 mL of distilled water to the precipitation glass and measure the temperature.
- Weigh 5 g of the corresponding solid, add it to the precipitation glass, and measure until the thermometer stabilizes at what temperature.
- Fill in the following table:
Theoretical explanation
Processes that release heat are called exothermic and those that absorb heat are called endothermic. In the first situation, the container heats up, and in the second situation, the container cools down.
Did you know that…? NEXCARE instant cold packs contain a smaller inner bag containing water and an outer bag containing a white solid, which is urea, CO(NH2)2. When you want to use them, you have to give them a strong hit so that the inner bag breaks and the urea dissolves. As it is obvious, these packs are for single use only.
