Salt and the Ocean

Atomically Speaking…• Ions are atoms with either more or less electrons

than protons and are therefore electrically charged.

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When water and salt mix…• Water dissolves salts by surrounding the atoms in

the salt molecule and neutralizing the bond holding the molecule together.

When water and salt mix…• Water dissolves salts by surrounding the atoms in the salt molecule and neutralizing the bond holding the molecule

together.

– Dissolved salts form cations (positively charged ions) and anions (negatively charged ions).

– The process of water surrounding an ion is called hydration.

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• Seawater consists of water with various materials dissolved within it.

– 1. The solvent is the material doing the dissolving and in seawater it is the water.

– 1. The solvent is the material doing the dissolving and in seawater it is the water.

– 2. The solute is the material being dissolved, and in seawater it is the salt.

– 1. The solvent is the material doing the dissolving and in seawater it is the water.

– 2. The solute is the material being dissolved, and in seawater it is the salt.

– 3. A solution is the combination of the solvent and solute.

– 4. Salinity is the total amount of salts dissolved in the water.

• a. It is measured in parts per thousand and is expressed as pptor abbreviated 0/00.

• How salty do you think the ocean is?

– 5. Average salinity of the ocean is about 35 0/00.

• Draw this diagram:

Not just one salt…• 99% of all the salt ions in the sea are sodium (Na+),

chlorine (Cl-), sulfate (SO4-2), Magnesium (Mg+2),

calcium (Ca+2) and potassium (K+).

Not just one salt…–1. Sodium and chlorine alone comprise

about 86% of the salt in the sea.

Not just one salt…–2. The major constituents of salinity display

little variation over time and are a conservative property of seawater. This means that what is taken out is replaced equally.

SALT OUT

SALT IN

Nutrients are chemicals essential for life

• 1. Major nutrients in the sea are compounds of nitrogen, phosphorus, and silicon.

Nutrients are chemicals essential for life

• 2. Because of usage, nutrients are scarceat the surface and their concentrations are measured in parts per million (ppm).

Nutrients are chemicals essential for life

• 3. Concentration of nutrients varies greatly over time and because of this they are considered a non-conservative property of the sea.

• This means that what is taken out is not replaced.

The sea contains dissolved gases, elements, and other compounds…

• In order of decreasing abundance the major gases in the sea are nitrogen, oxygen, carbon dioxide and the noble gases: argon (Ar), neon (Ne) and helium (He).

The sea contains dissolved gases, elements, and other compounds…

–1. Nitrogen and the noble gases are considered to be inert because they are chemically non-reactive. This means they like to be alone!

The sea contains dissolved gases, elements, and other compounds…• In order of decreasing abundance the major gases in the sea are nitrogen, oxygen, carbon dioxide and the

noble gases: argon (Ar), neon (Ne) and helium (He).

– 1. Nitrogen and the noble gases are considered to be inert because they are chemically non-reactive. This means they like to be alone!

• Trace elements occur in very small quantities and are usually measured in parts per million (ppm) or parts per billion (ppb).

– 1. Even in small quantities they are important in either promoting life or killing it.

Some of the trace elements of ocean water: Ag, Al, As, Au, B, Ba, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga Gd, Ge, Hf, Hg, Ho, In, K, La, Li, Lu, Mn, Mo, Na, Nb, Nd, Ni, Pa, Pb, Pd, Pr, Pt, Ra, Rb, Re, Ru, Sb, Sc, Se, Si, Sm, Sn, Ta, Tb, Th, Ti, Tl, Tm, V, W, Y, Yb, Zn, Zr.

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Quiz Next Class!

• Conservative Property of Seawater

• Solute

• Solvent

• Anion

• Inert

• Nutrients

• Non-Conservative Property of Seawater

• Solution

• Cation

• Ion

• Salinity

• Trace Elements

To Salinity and Beyond!

• Salinity in the ocean is in a steady-state condition because the amount of salt added to the ocean (input from source) equals the amount removed(output into sinks).

To Salinity and Beyond!• Salinity in the ocean is in a steady-state condition because the amount of salt added to the ocean (input from source)

equals the amount removed (output into sinks).

– 1. Salt sources include weathering of rocks on land and the reaction of lava with seawater.

To Salinity and Beyond!• Salinity in the ocean is in a steady-state condition because the amount of salt added to the ocean (input from source)

equals the amount removed (output into sinks).

– 1. Salt sources include weathering of rocks on land and the reaction of lava with seawater.

• a. Weathering mainly involves the chemical reaction between rock and acidic rainwater, produced by the interaction of carbon dioxide and rainwater forming carbonic acid.

• Salt sinks (drains on salinity) include the following:

– 1. Evaporation removes only water molecules.

• Salt sinks (drains on salinity) include the following:

– 1. Evaporation removes only water molecules.

• A. Remaining water becomes increasingly saline, eventually producing a salty brine.

• Salt sinks (drains on salinity) include the following:

– 1. Evaporation removes only water molecules.

• A. Remaining water becomes increasingly saline, eventually producing a salty brine.

• B. If enough water evaporates, the brine becomes supersaturate and salt deposits begin to precipitate forming evaporite minerals (HYDROGENOUS DEPOSITS!)

• Salt sinks (drains on salinity) include the following:– 1. Evaporation removes only water molecules.

• i. Remaining water becomes increasingly saline, eventually producing a salty brine.

• ii. If enough water evaporates, the brine becomes supersaturate and salt deposits begin to precipitate forming evaporite minerals (HYDROGENOUS DEPOSITS!)

– 2. Wind-blown spray carries minute droplets of saltwater inland.

• Salt sinks (drains on salinity) include the following:– 1. Evaporation removes only water molecules.

• i. Remaining water becomes increasingly saline, eventually producing a salty brine.

• ii. If enough water evaporates, the brine becomes supersaturate and salt deposits begin to precipitate forming evaporite minerals (HYDROGENOUS DEPOSITS!)

– 2. Wind-blown spray carries minute droplets of saltwater inland.

– 3. Absorption of ions onto clays and some authigenicminerals.

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• Salt sinks (drains on salinity) include the following:– 1. Evaporation removes only water molecules.

• i. Remaining water becomes increasingly saline, eventually producing a salty brine.

• ii. If enough water evaporates, the brine becomes supersaturate and salt deposits begin to precipitate forming evaporite minerals (HYDROGENOUS DEPOSITS!)

– 2. Wind-blown spray carries minute droplets of saltwater inland.

– 3. Absorption of ions onto clays and some authigenic minerals.

– 4. Shell formation by organisms.

Salt affects water’s unique properties…

• Addition of salt modifies the properties of water.

– 1. Pure water freezes at 0oC. Adding salt increasingly lowers the freezing point because salt ions interfere with the formation of the hexagonal structure of ice.

Demo Time!1. What is in the graduated cylinders at the front?

2. What did the egg do in #1? #2? #3?

3. What do you think is in each of cylinders?

4. What property of water is being affected in this demonstration?

5. What is the secret to cylinder #3?

Salt affects water’s unique properties…• Addition of salt modifies the properties of water.

– 1. Pure water freezes at 0oC. Adding salt increasingly lowers the freezing point because salt ions interfere with the formation of the hexagonal structure of ice.

– 2. Density of water increases as salinity increases.

Salt affects water’s unique properties…• Addition of salt modifies the properties of water.

– 1. Pure water freezes at 0oC. Adding salt increasingly lowers the freezing point because salt ions interfere with the formation of the hexagonal structure of ice.

– 2. Density of water increases as salinity increases.

– 3. The boiling point of water increases.

Videos

• http://www.jpl.nasa.gov/video/index.cfm?id=984

• http://app.discoveryeducation.com/player/view/assetGuid/1D6C88E0-C080-42BE-BB12-D8FEEEAB8399 (downloaded and emailed)

http://www.jpl.nasa.gov/video/index.cfm?id=984http://app.discoveryeducation.com/player/view/assetGuid/1D6C88E0-C080-42BE-BB12-D8FEEEAB8399