Chemical Properties of Seawater

Water is a Polar MoleculeBeing a “Polar Molecule” means that one end of the molecule is slightly negatively charged and the other end is slightly more positively charged

Water has Hydrogen BondingThis refers to the type of attraction seen in this polar molecule: the negative oxygen end of one water molecule being attracted to the positive hydrogen ends of another water molecule

Water demonstrates Adhesion & CohesionSince water is polar (has oppositely charged ends) it has a tendency to be attracted to other polar and non-polar molecules

Adhesion – hint: think of Adhesive Tape-we say it is “adhesive” when we use it to stick a piece of paper to our classroom door, or a person to a wall, for example

An example of water’s adhesiveness: when it adheres to and climbs up a glass forming a meniscus

Water demonstrates Adhesion & Cohesion, cont.Cohesion – hint: think of a team who works well together-we say they are a “cohesive” group when they stick together to make a great play, for example

An example of water’s cohesiveness: when one water molecule sticks to another water molecule to bubble over your glass without spilling (a handy trick of water’s that we call surface tension – the tendency of the top of a liquid to resist external forces)

Water has Relatively Low ViscosityViscosity is the measure of a fluid’s resistance to flow – water flows relatively easily (less easily than a gas, but more easily than many other fluids) What might influence viscosity?

-changes in temperature-changes in salinity-changes in pressure

Water has a specific DensityDensity is mass/volumeA density less than one means something is able to float in waterWater is most dense at 4⁰CWhat might influence density of seawater?

-Changes in temperature-Changes in salinity-Changes in pressure

Q: Which is more dense, seawater or freshwater? Why?

Solid vs. LiquidWhen water is a

liquid, its polar molecules are constantly moving and bonds are loose.

When water is a solid, its polar molecules are tightly bonded and form a solid lattice

This lattice is less dense and so solid water (ice) floats.

Water has a specific Heat CapacityHeat capacity is the amount of energy required to change the temperature of the water by a given amount

Important: The ocean is a “heat buffer”, meaning that it takes a REALLY long time to heat or cool the world’s oceans. They are really BIG so they hold whatever heat they do have for a LONG, LONG time…. Why?

Water’s polarity and its hydrogen bonds mean it takes a LOT of energy to change the temperature, even by 1⁰