THE PROPERTIES OF WATER THAT MAKE

LIFE ON EARTH POSSIBLE

Let’s Review!!

Copyright Amy Brown – Science Stuff

WATER HAS FOUR PROPERTIES THAT CONTRIBUTE TO EARTH’S ABILITY TO SUSTAIN ABUNDANT

LIFE. NAME THEM!

Water is very cohesive.

Water has the ability to stabilize temperatures on Earth.

Water expands upon freezing.

Water is a very versatile solvent.

This type of bond is formed when two atoms are sharing electrons.

Covalent bond

What is a polar covalent bond?

Covalent bonds in which electrons are shared unequally resulting in a molecule which has poles -- part of it is negative and part of it is positive.

Why are the electrons in this bond being shared unequally?

Because one of the atoms has a much higher electronegativity than the other.

What is electronegativity?

Electronegativity is the attraction between an atom and it shared

electrons.

Which atoms have the highest electronegativity?

The atoms with the highest electronegativity are found near the top, right hand corner of the periodic table,

excluding the noble gases.

Describe a polar molecule

A polar molecule contains a highly electronegative atom. The result is that one end of the molecule will have a slightly positive charge, and the other end will have a slightly negative charge.

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Water molecules will stick together because they are so polar. What is the force of attraction that exists between two water molecules?

Hydrogen Bonds!!!!!

Describe a nonpolar covalent bond.

In a nonpolar covalent bond, the electrons are shared equally between two atoms.These bonds are found in the diatomic molecules as well as between different atoms that have very similar electronegativities.

What happens in an ionic bond?

An ionic bond occurs when two atoms are so unequal in their attraction for valence

electrons that the more electronegative atom strips the shared electron completely

away from its partner.

What is a hydrogen bond?

A hydrogen bond is a weak molecular force formed between the hydrogen atom of one

molecule to a highly electronegative atom of another molecule.

Name the four properties that are responsible for getting water to the

top of a very tall tree.

Capillary actionCohesionAdhesion

Transpiration Pull

Define cohesion.

Cohesion is the attraction between “like” molecules.

Water molecules stick to other water molecules.

Define adhesion.

Adhesion is the attraction between “unlike”

molecules. The water molecules stick to the

sides of the xylem tubes.

What is transpiration pull?

Transpiration Pull: As one water molecule escapes through the stoma of a leaf, it exerts a tug or pull on the column of water below it. This helps to pull the water up the plant.

Define capillary action.

Capillary action is the movement of water within a small tube due to

adhesion and cohesion. The small tubes in the tree are called xylem.

Water has the ability to absorb and release large amounts of heat with only slight changes in it own temperature.

This is because water has a high _______.

Specific Heat

How does water moderate temperatures

on Earth?Water has the ability to absorb much of the sun’s

energy during the day, resulting in lower land temperatures.

Water releases much of this energy at night, warming the landmasses.

What effect does the high specific heat of water have on life in the bodies of water?

Life could not exist in bodies of water if there were drastic changes in

temperature.

It keeps water liquid at a wide range of temperatures.

Explain evaporative cooling.

Evaporative cooling is the property of a liquid whereby the surface becomes cooler during evaporation. The molecules of water with the highest kinetic energy are the most likely to leave as gas. The molecules left behind have less energy and therefore less heat.

Define: solvent and solute

Solvent: the part of a solution that does the dissolving

Solute: the part of the solution that gets dissolved

Define: hydrophobic and hydrophilic

Hydrophilic: polar molecules that readily dissolve in water; their polar regions attract water molecules and are easily broken apart

Hydrophobic: molecules that do not readily dissolve in water; they are nonpolar molecules that are not attracted to the polar regions of the water molecule; examples are fats and oils.

What is the range of the pH scale?

The pH scale ranges from 1 to 14.

Describe the condition that exists in a solution that has a pH of 7

pH of 7 = neutral; because the concentrations of H+ ions and OH- ions are exactly the same

Describe the condition that exists in a solution that has a pH > 7

pH above 7 = basic; because the concentration of OH- ions is greater than the H+ ions

Describe the condition that exists in a solution that has a pH < 7

pH below 7 = acidic; because the concentration of H+ ions is greater than the OH- ions

What are buffers?

Buffers are substances that minimize changes in pH and are

produced by the living cells in order to maintain a constant pH level

within the cells.

Created by Amy Brown – Science Stuff

Copyright © August 2012 Amy Brown (aka Science Stuff)

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