DISSOLVED SALTS IN THE OCEAN 4/14/17 DISSOLVED SALTS IN THE OCEAN Objective: I will explain how salt dissolves in water. PAGE 77
Dissolved Salts Sea salts form from 3 sources: Volcanic eruptions Chemical weathering of land rocks Chemical reactions between water and sea rocks
Structure of Salt (NaCl)
Structure of Salt (NaCl) salt (NaCl) is made up of a positive sodium ion and a negative chloride ion ion: atom with different # of electrons, giving it a charge More electrons- negative charge Less electrons- positive charge When many Na+ and Cl- attract each other, they form a salt crystal in the shape of a cube
Structure of Salt (NaCl)
The Water Molecule (H2O)
The Water Molecule (H2O) Two hydrogen atoms bonded to one oxygen atom Oxygen attracts the hydrogen’s electron, moving it to one side of the atom Therefore: oxygen side of the molecule has a – charge hydrogen side of the molecule has a + charge Known as a polar molecule
The Water Molecule (H2O)
The Water Molecule (H2O)
Dissolved Salts in Water
Dissolved Salts in Water When salt is put in water: Positive end of H2O attracts Cl- Negative end of H2O attracts Na+ This attraction pulls the salt cube apart
Dissolved Salts in Water
Dissolved Salts in Water
Dissolved Salts in Water NO CHEMICAL CHANGE TAKES PLACE! Only physical change If we evaporate the H2O, the salt will recombine This is why salt is left behind after evaporation
Dissolved Salts in Water Salinity is a measure of the amount of dissolved salts in water Salinity is not homogenous (uniform) across the Earth’s oceans Both salinity and temperature affect the density of seawater ON average salt water is 96.5% pure water and 3.5% compounds including dissolved salts
Dissolved Salts in Water
Dissolved Salts in Water Three primary factors influence salinity: 1. Freshwater input - High rates of freshwater input (river inflow to the sea; melting ice) will decrease salinity 2. Evaporation - High rates of evaporation will increase salinity 3. Precipitation - High levels of rainfall will decrease salinity
Dissolved Salts in Water Three primary factors influence salinity: 1. Freshwater input - High rates of freshwater input (river inflow to the sea; melting ice) will decrease salinity 2. Evaporation - High rates of evaporation will increase salinity 3. Precipitation - High levels of rainfall will decrease salinity
Dissolved Salts in Water Lake Retba, the Pink lake of Senegal. Pink color is caused by Dunaliella salina algae. Salinity is 40% in some areas.
Dissolved Salts in Water Baltic Sea Salinity is 1% in some areas
Dissolved Salts in Water What happens when water at different depths has different densities? Layers of water will form Formation of layers is part of the reason we have ocean currents
Output Activity (page 76) Draw Figure 5. of ocean layers on page 498 in the YELLOW Earth Science book. Add color! Make sure the diagram is big and detailed. Draw one fish...