Unit 4 – Toxins, Schemes and Mind Maps of Reasoning

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Unit 4 – Toxins

Part 1 – Toxic Changes Part 2 – Measuring Toxins Part 3 – Toxins in Solution Part 4 – Acidic Toxins Part 5 – Toxic Cleanup

Unit 4 Part 2

Measuring Toxins

ChemCatalyst 4 - 7

Which substance do you think is most

toxic to you?

 alcohol (ethanol, C

2

H

6

O)

 aspirin (salicylic acid, C

7

H

6

O

3

 arsenic (III) oxide (As

2

O

3

Explain your thinking.

Toxicity  Toxicity depends on two quantities: amount of toxic substance and mass of the organism.  Other factors besides dosage also play a role in toxicity: method & site of delivery, species of organism, body mass  All substances are toxic in large enough doses, even sugar and water.

Reflection! Methadone is a medication used as a painkiller and as a treatment for those recovering from heroin addiction. The LD 50 for methadone is 95 mg/kg.

1. Would you consider methadone to be more or less toxic than acetaminophen (LD 50 = 2404 mg/kg)? than aspirin (LD 50 = 200mg/kg)?
2. Explain how you would calculate the amount of this substance that would be lethal to a 120 lb human.

75 – Counting by Weighing

EQ: How can mass be used to

count large numbers of small

objects?

Using Mass to Count  The easiest way to determine the count of very small objects is to find their total mass and divide by the mass of one object.  In order to get a more accurate average mass measurement for a tiny object, it is better to find the mass of 10 or 20 of the objects and divide by the number of objects to find the average mass, especially if the variation in size is slight.

Percent Error  Chemists use mass when measuring chemical compounds because it is not possible to count atoms directly.  Chemists use percent error to express how close their measurements are to the accepted value. Percent error = |observed value – actual value| • 100 actual value

ChemCatalyst 4 - 9

 Which do you think is more

toxic, 1 mole of arsenic, As, or

10 g of arsenic. Explain your

reasoning.

The Mole  Instead of counting individual atoms, groups of atoms are often times counted together in moles  1 mole = Avogadro’s number  1 mole = 6.02 × 10 23 atoms

Scientific Notation  A number in standard notation can be converted to scientific notation by writing it as a decimal with one digit to the left of the decimal point times a power of ten.

1.56 X 10

4

= 15,600 1.56 X 10

• 4

Move the decimal point four places to the right. Move the decimal point four places to the left.

Suppose you have 1 mol of lead, Pb, 1 mol of lead (II) chloride, PbCl 2 , and 1 mol of lead (II) carbonate, PbCO 3. What is the mass of each sample?

77 – Molar Mass

EQ: How can you convert between mass and moles?

ChemCatalyst 4 - 10

Consider 12 nickels, 2 empty aluminum

cans, and a balloon full of carbon dioxide

gas.

1. Which has the greatest mass?

2. Which has the greatest number of

atoms?

3. Which has the greatest number of

moles of atoms?

Explain the reasoning behind your

answers.