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2.3 Chemistry of Water
An ionic bond and a covalent bond can be compared.
Water's solid, liquid, and vapor states allow life to exist on Earth.
The top formula shows that when water forms, an oxygen atom is sharing electrons with two hydrogen atoms.
The ball-and-stick model shows that the bonds between oxygen and hydrogen are at an angle.
The three-dimensional shape of the molecule is given by the space-filling model.
The shape of the molecule is not indicated by the electron model.
The ball-and-stick model shows that there are two bonds in a water molecule.
The V shape of a water molecule is shown in the space-filling model.
Water has hydrogen bonding between it.
Each water molecule has the ability to bond with up to four other molecule.
Water forms and breaks hydrogen bonds when it is in a liquid state.
In biology, structure relates to function.
This is true at many levels, including water.
Different shapes of hormones allow them to be seen by the cells in the body.
The way a key fits a lock and the shapes of disease-causing agents can only be removed with the help of antibodies.
Because carbon dioxide is symmetrical, the opposing charges cancel one another and hydrogen bonding does not occur.
The dotted lines show that the hydrogen atoms in one water molecule are attracted to the oxygen atoms in other water molecule.
The hydrogen bonds are weaker than the ionic or covalent bonds.
The dotted lines show that hydrogen bonds are more difficult to break.
Water has hydrogen bonding.
Other biologicalmolecules, such as DNA, have polar covalent bonds involving hydrogen and oxygen.
There can be a hydrogen bond between the same molecule and nearby ones.
A single hydrogen bond is more difficult to break than a single covalent bond.
Cells have hydrogen bonds that help maintain their structure and function.
The two strands of DNA are held together by hydrogen bonds.
When a copy of itself is made, hydrogen bonds can easily break.
The hydrogen bonds add stability to the molecule.
The shape of a molecule is maintained by hydrogen bonding between different parts.
Many of the important properties of water are the result of hydrogen bonding.
All living organisms are 70% water.
Water has unique chemical properties because of hydrogen bonding.
Without hydrogen bonding between molecule, water would freeze at -100degC and boil at -91degC, making most of the water on Earth steam, and life unlikely.
Water is a liquid at temperatures found on the Earth's surface.
It is cold at 0degC and hot at 100degC.
The chapter opener states that the search for life on other planets often begins with the search for water.
The amount of heat energy needed to raise the temperature of 1 g of water is called A.
In comparison, other covalently bonding liquids only need half the amount of energy to rise.
Water is able to absorb heat without the temperature changing.
The loss of 80 calories of heat energy is required to convert 1 g of liquid water to ice.
The temperature of water falls more slowly than that of other liquids.
The property of water is important for all life.
At naturally occurring environmental temperatures, water can be a solid, liquid, or gas.
Water is a liquid at room temperature and pressure.
When water becomes ice, it gives off heat, which can help keep the temperature higher than expected.
When water is evaporates, it takes up a lot of heat as it changes from a liquid to a gas.
splashing water on the body will keep the temperature within a normal range.
When water is boiled, it becomes liquid, meaning that it goes into the environment.
540 calories of energy is required to convert 1 g of the hottest water to a gas.
Water has a high temperature because hydrogen bonds must be broken before it can boil.
Animals in a hot environment can release excess body heat by using water's high heat of vaporization.
Body heat is used to cool the animal when it sweats or gets splashed.
During the summer and winter, the ocean absorbs and stores solar heat.
Water facilitates chemical reactions both outside and inside living systems.
It is a great solvent because of the number of polar substances it is capable of dissolving.
solutes are dissolved substances.
When ionic salts are put into water, the negative ends of the water molecule are attracted to the sodium ion, and the positive ends of the water molecule are attracted to the chloride ion.
The attraction causes the sodium and the chloride to separate.
Water is a solvent for ammonia.
At any moment in time, a water molecule can form hydrogen bonds with other water molecule.
Water flows freely, yet water does not separate from each other.
The water's polarity is the reason for this.
Multicellular animals have internal vessels in which water helps the transport of vitamins and minerals because they have the same chemistry as the cardiovascular system.
The liquid portion of our blood, which transports dissolved and suspended substances about the body, is only 10% water.
The transport of water in plants is aided by cohesion and adhesion.
Plants have roots in the soil that absorb water, but the leaves are exposed to solar energy.
Water from transport vessels that extend from the roots to the leaves is replaced with water from the leaves.
A tension is created that pulls the water column up from the roots.
Adhesion of water to the walls of the transport vessels helps keep the water column from breaking apart.
Section 25.3 will discuss capillary action as essential to plant life.
Water is cohesive and strong.
The movement of water in a plant is dependent on cohesion and adhesion.
Plants need this capillary action to function.
Page 30 cling together when the liquid surface is exposed to air because they are attracted to each other.
Humans can skip rocks on water because of its high surface tension.
Water striders can walk on the surface of a pond without breaking it.
The molecule come closer together as liquid water cools.
The water is dense at 4degC.
hydrogen bonding becomes more rigid but also more open at temperatures below 4 degrees.
Cans of soda burst when placed in a freezer, or frost heaves make northern roads bumpy in the winter, because water expands as it reaches 0degC.
It also means that ice floats on liquid water.
Water is denser than ice.
The water is denser at 4degC.
Water expands when it freezes because the hydrogen bonds in water are farther apart than in liquid water.
The property of water allows ice to flow, providing habitats for some aquatic species and protecting other species that live beneath the ice.
If ice did not float on the water, it would sink to the bottom, making life impossible in the water and on land.
The ice on the water acts as an insulation to keep the water below it from freezing.
The winter allows aquatic organisms to survive.
It helps prevent a sudden change in temperature by drawing heat from the environment.
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