Chapter 3 - Physical Properties of Ocean Water Focused Notes
Topics:
The Unique Nature of Water pg. 40-43
Temperature, Salinity, and Density pg. 45-46
Dissolved Gases – pg. 46-48
Transparency and Pressure – pg. 48-49
Stability and Overturn pg. 49-51
The Unique Nature of Water pg. 40-42
Questions to answer:
1. What are water molecules made of and what makes them unusual? Water molecules are made of 2
hydrogen atoms and 1 oxygen atom. They are unusual because they attract each other – the hydrogen
ends have a slightly positive charge and the oxygen ends have a slightly negative charge and opposite
charges attract.
2. What are hydrogen bonds? Hydrogen bonds are the bonds that attract water molecules, they are weak
so they constantly break apart and then reform.
3. Describe the relationship between temperature and the states of water molecules. Water is found in all
3 states on earth, solid, liquid, and gas. As you add heat to the solid it causes the molecules to move
farther apart and faster until it changes state - physical change. If you take away heat you can slow the
molecules down and cause it to change shape too. Temperature is the reflection of the average speed of
the molecules. The faster they move, the higher the temp.
4. What happens to the hydrogen bonds when water turns from a liquid to a vapor? The energy from the
temperature increase causes the bonds to break and the molecules to move apart and move faster.
5. What happens to the density of water when it turns to ice (becomes a solid)? Water molecules expand
when they form a solid (ice) and this causes them to become LESS dense and therefore float.
6. Define heat capacity and discuss the heat capacity of water. The amount of heat needed to raise a
substances temperature by a given amount is heat capacity. Water has one of the highest heat capacities
of any naturally occurring substance.
7. Why is water called the Universal Solvent? Water can dissolve more things than any other natural
substance and is therefore called the universal solvent.
Temperature, Salinity, and Density pg. 45-46
Questions to answer:
1. What determines the density of seawater? The density of seawater is determined by
temperature primarily but also salinity and other items that may be dissolved in it.
2. Why is ocean water less prone to freezing than river or lake water? Ocean water is less prone to
freezing than rivers or lakes due to it’s salinity levels. Salt water freezes at a lower temperature (colder) than
freshwater.
3. Which physical property determines density the most, temperature or salinity? Temperature
determines the density the most because it is the most variable physical property.
Dissolved Gases – pg. 46-48
Questions to answer:
1. What are the three most important gases in the ocean? Oxygen, carbon dioxide, and nitrogen are the
most important gases in the ocean.
2. Explain the process of gas exchange. Gas exchange is the process where elements and compounds are
transferred from the atmosphere to the ocean water and back again. These are a huge part of the carbon, nitrogen, and
oxygen cycle.
3. What type of water do gases dissolve best in? Unlike solids, gases dissolve better in cold water than
warm water.
4. Why is the dissolved oxygen level in the oceans much lower than the dissolved carbon
dioxide levels? Oxygen gas is not very soluble in water but carbon dioxide is because it reacts
chemically when it dissolves.
5. What happens to most of the oxygen produced by photosynthetic organisms in the ocean? Most of the
oxygen produced by photosynthetic organisms in the ocean is released into the atmosphere.
Transparency and Pressure – pg. 48-49
Questions to answer:
1. Why is transparency so important to marine organisms? Transparency means that light can travel
through it and this is required for photosynthetic organisms (phytoplankton) to be able to produce their own food.
2. What color light is absorbed the least by ocean water? Blue is not absorbed so it is refracted and that
is why the ocean looks blue.
3. Why do things that appear red at the surface appear black in deep water? There is no red light to
reflect off them and be seen.
4. How does the amount of material dissolved or suspended in water affect the transparency?
The more particles that are dissolved in the water the less transparent the water is and that affects the rate of
photosynthesis.
Pressure
Questions to answer:
1. Describe what “1 atmosphere” of pressure means. An atmosphere is equal to 14.7 psi of pressure and
is equal to the amount of pressure that exists from the air column pressing down on our heads when we are on land.
2. How many feet of water depth add another atmosphere of pressure? 33.3 ft or 10 meters
3. What happens to gas filled structures like lungs when they go too deep in the ocean? They collapse
from the pressure around them being greater than the pressure they exert.
4. Why is pressure a limitation to exploring the deep ocean? It take special technology, with lots of
difficulty, expense, and danger to explore an area with that significant an amount of pressure.
Stability and Overturn pg. 49-51
1. Explain what stratified means and how it applies to ocean water layering Stratified means layered. The ocean
water is stratified where the most dense water is found on the bottom and the least dense water is found on the
top .
2. Differentiate between deep water and surface water. Deep water is usually cold and dense and surface water is
usually warm and “light”.
3. Define the terms downwelling, overturn and thermohaline circulation
a. downwelling: the process when surface water sinks
b. overturn: happens when surface water sinks and displaces the deeper colder water.
c. thermohaline circulation: the circulation of water based on changes in temperature and salinity.