1. Composition of Ocean Oceans 11

2. Composition Seawater is made up of water (H2O) and dissolved salts. Seawater is made up of water (H2O) and dissolved salts. As good a solvent as seawater is, there is a limit to how much of a given salt it can hold. For regular salts like halite (NaCl) and sylvite (KCl), that limit is very high, but for some materials like iron (Fe) and silver (Ag) that limit is low. When water has dissolved as much of a given compound as it can hold, the water is saturated with respect to that compound. If more of the compound is added to the water, it will not dissolve but will just sink to the bottom. If some of the water is removed by freezing or evaporation, the dissolved ions will sink to the bottom. This is called precipitation. As good a solvent as seawater is, there is a limit to how much of a given salt it can hold. For regular salts like halite (NaCl) and sylvite (KCl), that limit is very high, but for some materials like iron (Fe) and silver (Ag) that limit is low. When water has dissolved as much of a given compound as it can hold, the water is saturated with respect to that compound. If more of the compound is added to the water, it will not dissolve but will just sink to the bottom. If some of the water is removed by freezing or evaporation, the dissolved ions will sink to the bottom. This is called precipitation.

3. Density Density is a measure of how mass is distributed. A pound of feathers and a pound of lead have the same weight, but the pound of feathers takes up much more space, because feathers are less dense. Density is a measure of how mass is distributed. A pound of feathers and a pound of lead have the same weight, but the pound of feathers takes up much more space, because feathers are less dense. Fresh water has a density of one gram per cubic centimeter (1 g/cm3). Seawater is more dense than fresh water, because the ions dissolved in seawater are made up of atoms that are denser than hydrogen and oxygen, the components of water. Fresh water has a density of one gram per cubic centimeter (1 g/cm3). Seawater is more dense than fresh water, because the ions dissolved in seawater are made up of atoms that are denser than hydrogen and oxygen, the components of water.

4. Temperature Fresh water freezes at 0°C and boils at 100°C. The dissolved ions in seawater make it harder to freeze, because the ions get in the way when the water molecules arrange themselves into ice crystals. This means that seawater has a lower (colder) freezing point than fresh water. Likewise, the dissolved ions also make seawater harder to evaporate. Fresh water freezes at 0°C and boils at 100°C. The dissolved ions in seawater make it harder to freeze, because the ions get in the way when the water molecules arrange themselves into ice crystals. This means that seawater has a lower (colder) freezing point than fresh water. Likewise, the dissolved ions also make seawater harder to evaporate. For both freezing and evaporation of seawater, the ions will stay in the liquid water. Ice and water vapor aren't good solvents at all; they can't hold the ions. So, when water freezes at the poles, the ice is pure while the sea water it forms from gets relatively saltier. For both freezing and evaporation of seawater, the ions will stay in the liquid water. Ice and water vapor aren't good solvents at all; they can't hold the ions. So, when water freezes at the poles, the ice is pure while the sea water it forms from gets relatively saltier.

5. Salinity The salinity of seawater is a measure of the amount of dissolved stuff present in the water. Fresh water has a salinity near zero, while the oceans range in salinity from about 3.3% to 3.7% by weight. That is, of every 100 grams of ocean water, about 3.5 of them are actually made up of dissolved ions, while 96.5 of them are water. The salinity of seawater is a measure of the amount of dissolved stuff present in the water. Fresh water has a salinity near zero, while the oceans range in salinity from about 3.3% to 3.7% by weight. That is, of every 100 grams of ocean water, about 3.5 of them are actually made up of dissolved ions, while 96.5 of them are water. There are about 70 different elements dissolved in seawater, but only 6 major ones. There are about 70 different elements dissolved in seawater, but only 6 major ones.

7. Questions 1. What is the composition of seawater? 1. What is the composition of seawater? 2. How many elements are dissolved in seawater? 2. How many elements are dissolved in seawater? 3. What does it mean when water is saturated? 3. What does it mean when water is saturated? 4. What does salinity measure? 4. What does salinity measure? 5. On average, what is the salinity of most oceans? 5. On average, what is the salinity of most oceans? 6. Which is the most abundant element in seawater? 6. Which is the most abundant element in seawater? 7. Which is denser, fresh water or seawater? 7. Which is denser, fresh water or seawater? 8. How does the freezing point of seawater compare to that of freshwater? 8. How does the freezing point of seawater compare to that of freshwater? 9. What happens to the salt concentration of seawater when it freezes (ie, at the poles)? 9. What happens to the salt concentration of seawater when it freezes (ie, at the poles)? 10. What are the three main sources of salts that are dissolved in seawater? 10. What are the three main sources of salts that are dissolved in seawater?

8. Solutions 1. Water + dissolved salts 1. Water + dissolved salts 2. 70 altogether, but 6 common ones 2. 70 altogether, but 6 common ones 3. Water is saturated when it can hold no more of a particular element. 3. Water is saturated when it can hold no more of a particular element. 4. Salinity measures the % of salt dissolved. 4. Salinity measures the % of salt dissolved. 5. Average salinity is 3.5% 5. Average salinity is 3.5% 6. Most abundant element is chlorine. 6. Most abundant element is chlorine. 7. Seawater is more dense. 7. Seawater is more dense. 8. Seawater has a lower freezing point. 8. Seawater has a lower freezing point. 9. The salt concentration in the water increases. 9. The salt concentration in the water increases. 10. 3 mains sources: volcanic eruptions, weathering down of continents, volcanic rocks. 10. 3 mains sources: volcanic eruptions, weathering down of continents, volcanic rocks.