Click the plus sign to learn about how the ocean became salty
Click the plus sign to learn what salinity is
Click the plus sign to learn about water's role as a solvent
How the Ocean Became Salty
The ocean's saltiness is the result of geological processes that have taken place over millions of years:
- Runoff from Land: Rain dissolves minerals from rocks on land, and rivers carry these salts into the ocean.
- Vents in the Seafloor: Hydrothermal vents on the ocean floor release hot, mineral-rich fluids from the Earth's crust directly into the seawater.
- Evaporation: Water evaporates from the ocean's surface but leaves the salts behind, causing the salt concentration to gradually increase over time.
Over millions of years, these processes have increased the ocean’s salinity, which also affects how dense the water is.
Water as a Solvent
A solvent is a liquid that can dissolve other substances. Water is often called the "universal solvent" because it's so good at this job. Its secret lies in its molecules, which are polar. They act like tiny magnets, with one end having a slight positive charge and the other end having a slight negative charge. Salt is made of charged particles called ions. In salt, you have positive sodium ions (Na⁺) and negative chloride ions (Cl⁻) that stick together because opposites attract.
When you drop salt into water, the "magnet-like" water molecules surround the salt's ions. The positive ends of the water molecules pull on the negative chloride ions, while the negative ends of the water molecules pull on the positive sodium ions. This tug-of-war is strong enough to break the salt crystal apart, completely separating the ions and mixing them into the water, which is what it means for the salt to dissolve. Because of its polarity, water is excellent at dissolving not just salts, but also other polar substances like sugar.
Salinity
Salinity is the amount of dissolved salts in water.
Q1/3 W2 Salinity of Water
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Transcript
Click the plus sign to learn about how the ocean became salty
Click the plus sign to learn what salinity is
Click the plus sign to learn about water's role as a solvent
How the Ocean Became Salty
The ocean's saltiness is the result of geological processes that have taken place over millions of years:
Over millions of years, these processes have increased the ocean’s salinity, which also affects how dense the water is.
Water as a Solvent
A solvent is a liquid that can dissolve other substances. Water is often called the "universal solvent" because it's so good at this job. Its secret lies in its molecules, which are polar. They act like tiny magnets, with one end having a slight positive charge and the other end having a slight negative charge. Salt is made of charged particles called ions. In salt, you have positive sodium ions (Na⁺) and negative chloride ions (Cl⁻) that stick together because opposites attract.
When you drop salt into water, the "magnet-like" water molecules surround the salt's ions. The positive ends of the water molecules pull on the negative chloride ions, while the negative ends of the water molecules pull on the positive sodium ions. This tug-of-war is strong enough to break the salt crystal apart, completely separating the ions and mixing them into the water, which is what it means for the salt to dissolve. Because of its polarity, water is excellent at dissolving not just salts, but also other polar substances like sugar.
Salinity
Salinity is the amount of dissolved salts in water.