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Norma Roberts is a family friend from an Italian neighborhood in Boston. When
cooking pasta, she always adds a few teaspoons of salt to the boiling water before
cooking the pasta. She claims, in her Boston accent, “it helps the pahster cook
fastah.” We all know that adding a solute to water increases its boiling point, but
what real effect will a few teaspoons of table salt have on the cooking time?
Normal Boiling Point of H2O = 100ºC
Kb for H2O = 0.52 oC/molal
1. Assuming that “a few teaspoons” of table salt (NaCl) is equal to 15.0 grams, and
my friend uses 4.0 liters of water in a 5.0 L pot to cook her pasta, calculate the
change in the boiling point when adding that much salt.
2. Do you think my friend is correct in asserting that the “pahster” will cook
“fahsta” in this situation? Defend your response.
3. An increase of 10.0 oC in water’s boiling point would cut the cooking time in
half. How many grams of salt would be required to accomplish this? Would this
be practical? (Use the same water and the same pot.)
SC7. Students will characterize the properties that describe solutions and the nature of acids and bases.
a. Explain the process of dissolving in terms of solute/solvent interactions:
(i.) Observe factors that affect the rate at which a solute dissolves in a specific solvent.
(iv.) Relate molality to colligative properties.