# Chemistry: Salinity

Warm Up: Write the formulas for M, m, % by weight, and salinity (ppm).

Learning Objective: Using salinity to determine freezing point of salt water.

Agenda: Practice problems

Table quiz

Ice caps and Global warming video.

Salt water comes in a variety of concentrations and there is a name for each;

Water salinity based on dissolved salts
Fresh water Brackish water Saline water Brine
< 0.05% 0.05–3% 3–5% > 5%

For this exercise,  use the following values;

FRESH WATER BRACKISH WATER SALINE WATER BRINE
0.025% 1% 3.5% 7%

Q1: convert concentrations from % to ppt

a) Fresh Water

b) Brackish Water

c) Saline

d) Brine

Q2: Calculate the molal concentration for a – d

a) Fresh Water

b) Brackish Water

c) Saline

d) Brine

Q3: Write the formula for freezing point depression of water (hint: the coefficient Kf = 1.86 degree C/m)

Q4: How many ions does 1 molecule of salt create when it is dissolved in water?

Q5: The freezing point of water is 0 degrees C (32 deg F), calculate the freezing point depression for a – d

a) Fresh Water

b) Brackish Water

c) Saline

d) Brine

Q6: Calculate the freezing point for a-d

a) Fresh Water

b) Brackish Water

c) Saline

d) Brine

This completes the quiz.

Salinity reference:

Earth Science: