In the first lesson of Chapter 14, students were introduced to the concept of LD50 (the dose of a compound that is lethal to 50% of the population).  As our entry task, students considered the following:

Which substance do you think is most toxic to you –

  1. Alcohol (ethanol, C2H6O)
  2. Aspirin (salicylic acid, C7H8O3)
  3. Arsenic (III) oxide (As2O3)

Explain your thinking

We then identified the LD50 values for all three substances using the Lethal Doses Handout.  We discussed the meaning of LD50 (the lethal dose at which 50% of rats die after exposure to a given amount of a substance, often expressed in mg/kg) and students were shown a Material Safety Data Sheet (MSDS) for water (toxic at >90 mL/kg), providing students with evidence that all substances are toxic at high enough levels.

Students then received the Lesson 74 Worksheet to work on during class time and they were assigned Lesson 74 textbook questions 1-5.

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