© 2002 Brooks/Cole, a division of Thomson Learning, Inc. Water and Ocean Structure

Review the Hydrogen Bond Why is there a hydrogen bond? ANSWER: ___________________________________ Properties of water due to H bond: 1. Cohesion 2. Adhesion 3. Dissolves many solids easily (universal solvent) 4. Absorbs red light, scatters blue, water is blue 5. Unique thermal properties....

Unique Properties of Water or What make water so special? Water exists in all three forms. If not for this bonding, the boiling point would be around –68 0 C while the freezing point would be C

Thermal Properties of Water Heat is a measure of how many molecules in a substance are vibrating and how rapidly they are vibrating Temperature measures only how rapidly they are vibrating.

For example, a candle flame has a higher temperature, but a tub full of hot water has more heat.

Specific Heat is the heat required to raise the temperature of 1g of a substance by 1  C. It is measured in calories per gram, cal/g (a calorie is the amount of heat required to raise the temperature of 1 gram of pure water 1 0 C) 1000 calories = 1 Calorie (food) Specific Heat raises Temperature

Water has a very high specific heat which means it resists changing temperature when heat is added or removed. (second highest of all known substances- liquid ammonia is higher)

Latent Heat changes the phase Latent Heat is the amount of energy needed to change the phase of water. Latent Heat is the amount of energy needed to change the phase of water. This is the energy used to break the hydrogen bonds and go from a solid to a liquid, and from a liquid to a gas without changing the temperature.

Why the difference between latent heats? In order to melt water, all the hydrogen bonds do not have to be broken. In order to vaporize water, ALL the bonds must be broken.

Latent Heat of Melting/Fusion For ice to melt, heat must be added to ice in the solid state. Once ice reaches 0°C, an input of 80 cal/gram is needed to break the hydrogen bonds and melt the ice. second highest for all known substances (only liquid ammonia is higher)

For water to evaporate, heat must be added to water in the liquid state. After water reaches 100  C, an input of 540 cal/gram is required to break the hydrogen bonds and allow evaporation. Water has the highest latent heat of vaporization of any known substance. Latent Heat of Vaporization

The tendency of a substance to resist change in temperature with the gain or loss of heat energy Thermal Inertia

These properties tend to moderate temperatures so that the oceans at the equator do not boil away. They also do not allow all the water on Earth to become part of the ice caps.

Seawater Chemistry

The oceans contain around 5.5 trillion tons of salt The oceans contain around 5.5 trillion tons of salt Salinity in the ocean varies from 33 ppt to 37 ppt – average 35 ppt Salinity in the ocean varies from 33 ppt to 37 ppt – average 35 ppt

© 2002 Brooks/Cole, a division of Thomson Learning, Inc. The Dissolving Power of Water

How Does Salinity change the thermal properties of Water? Increasing Salinity disrupts the hydrogen bonds between molecules, decreasing the specific heat needed to change temperature and decreasing the freezing point

Major Constituents of Seawater In one kilogram of water: g oxygen O g hydrogen H g chloride Cl g sodium Na g sulfate S g sulfate S g magnesium Mg g magnesium Mg g calciumCa g calciumCa g potassiumK g potassiumK

© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

The Principle of Constant Proportions Forchhammer’s principle states that although the salinity of various samples of seawater may vary, the ratio of major constituents is constant. Forchhammer’s principle is also known as the principle of constant proportions.

Measuring Salinity Salinity can be measured through electrical conductivity. When all other factors (temperature and pressure) are controlled for, the conductivity of water is dependent on salinity

A salinometer is used and can measure differences of 0.001%

Determining Salinity 2. Salinity can also be measured by the refraction of light as it passes through salt water. A Refractometer is used, light will bend more as it passes through salt water

Determining Salinity From space From space Aquarius Satellite launched in 2011 Aquarius Satellite launched in 2011 Uses microwave technology to determine electrical conductivity Uses microwave technology to determine electrical conductivity

Nansen Bottle

Nisken Bottle