Lesson 3.2: Salinity *Refer to Chapter 8 in your Textbook

Learning Goals: I can differentiate between compounds, mixtures, and solutions. I can explain why the ocean is salty. I can explain how marine organisms osmoregulate.

Compounds Compound: a substance formed by the chemical combination of two or more elements using ionic bonds Na (Sodium) + Cl (Chlorine)  NaCl (Salt)

Mixtures Mixture: two or more elements or compounds that are physically combined but not chemically combined Suspensions: material that does not dissolve in a mixture

Solutions Solution: two or more elements or compounds that are mixed completely Solute: substance being dissolved (ex. salt) Solvent: dissolver (ex. water) Solute + Solvent = Solution

Solubility Solubility: A solutes ability to be dissolved in a solvent As temperature increases, solubility increases (Ex. Sugar dissolves better in hot coffee over iced)

Salinity The ocean is a solution of water and dissolved materials Salinity is the measure of dissolved solids in the water Average salinity of the ocean = 35 ppt PPT = “parts per thousand” grams of salt per liter water

Types of Dissolved Solids Majority is table salt: Sodium Chloride (NaCl) Dissolved Solids in the Ocean: Chloride (Cl) 18.98 grams Sodium (Na) 10.56 grams Sulfate (SO4) 2.65 grams Magnesium (Mg) 1.28 grams Other 0.61 grams Calcium (Ca) 0.4 grams Potassium (K) 0.38 grams Bicarbonate (HCO3) 0.14 grams

Where does the Salt Come From? Water is an excellent solvent, which implies that wherever there is water, it is carrying materials with it 1) From land: Particles transported via freshwater streams and rivers 2) From the atmosphere: Particles transported via wind 3) From inside the Earth: Minerals are spewed out of volcanoes and hydrothermal vents

How does Salinity & Temperature Affect Density? Salinity & Density: The greater the salinity, the greater the density The greater the density, the better you float Temperature & Density: The lower the temperature, the greater the density Cold, salty water sinks!

Salinity and Marine Organisms Osmosis The movement of solvent through a semipermeable membrane to an area of higher solute concentration Moves High-to-Low

Salinity and Marine Organisms Hypertonic: water out, causes shriveling Isotonic: neutral Hypotonic: water in, causes swelling

Salinity and Marine Organisms Freshwater Fish: Put in saltwater would be a hypertonic solution, causing the fish to shrivel & dehydrate Saltwater Fish: Put in freshwater would be a hypotonic solution, causing the fish to swell and burst from water pressure

Salinity and Marine Organisms Osmoregulation: balancing the amount of water and salt in your body to remain isotonic Freshwater Fish: Gain water through osmosis & food Absorb salt through gills & food Dilute watery urine Saltwater Fish: Gain water and salt through eating and drinking Lose water and salt through osmosis Salty urine

Osmoregulation