Water's Life Supporting Properties

Water's Life Supporting Properties

Mrs. Nebzydoski's Biology Class

Atoms form bonds to acheive 8 electrons in their outer shells

• Covalent Bonds

• Ionic Bonds

Ionic Bond

Electrons are transferred between atoms

Positive and Negative Ions attact one another

Covalent Bond

Electrons are shared between atoms

Multiple Choice

In an ionic bond, electrons are

• transferred between atoms, creating a positive or a negative particle

• shared between two atoms

Multiple Choice

In a covalent bond, electrons are

• shared between two atoms

• transferred between two atoms

Not all electrons are shared evenly....

This leads to Polar Bonds

In a polar molecule

• Electrons are not shared evenly

• One side of the molecule appears to have a positive charge

• One side of a molecule appears to have a negative charge

WATER IS A POLAR MOLECULE

• The oxygen atom has a stronger hold on the shared electron than hydrogen

• The oxygen in water appears negative

• The hydrogen in water appears positive

Polar Water Molecules "stick" together

We call this property of water COHESION

The polarity of water leads to its "Life Supporting Properties" of:

• cohesive forces

• ability to moderate temperature

• ice is less dense than water

• water is the universal solvent

Cohesion and Adhesion

• water molecules stick to each other (cohesion)

• water molecules stick to other things (adhesion)

• surface tension allows water striders to "walk" on water due to cohesion

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Multiple Choice

Water molecules sticking to themselves is a property known as

• adhesion

• cohesion

Cohesion and Adhesion are important for life

• Adhesion allows water to get from the roots of the tree up to the top branches of the tree

• Cohesion allows water molecules to leave from the leaves of a tree through transpiration

• 
  

Cohesion and Adhesion

Because water is a polar molecule...

Water can regulate temperature changes

• It has a high specific heat (resists change in temperature)

• Bodies of water hold their heat (or lack there of) to regulate temperature of organisms living in them

Evaporative cooling

When you are sitting on the beach or by a pool on a 90 degree day, you are hot. If you get into the water and then back out, you will no longer feel hot. This is because of evaporative cooling.

It is still 90 where you are sitting, but as the water goes from liquid to gas form on your skin, it takes energy. That energy leaves your body and "cools" you down.

Multiple Choice

The ability of water to stick to itself is called

• adhesion

• cohesion

• specific heat

• evaporative cooling

Multiple Choice

When water evaporates off of your skin, it _____ you.

• warms

• cools

Multiple Choice

As water leaves a plant leaf, through transpiration, it is utilizing

• adhesion

• cohesion

• specific heat

• evaporative cooling

Solid water (ICE) is less dense than liquid water

• Ice floats!

• As water molecules come together in a solid form, there is a lot of empty space (this causes a lower density)

• If ice sank: ponds, lakes, and even the oceans would freeze solid

Water is the universal solvent

• Because water is polar, it dissolves many things

• Solvent: substance that does the dissolving

• Solute: substance that is dissolved

Water molecules surround ions

• When water molecules surround positive and negative ions the crystal "breaks" apart

• Minerals, sugars, and salts are just a few of the solutes that dissolve in water to sustain life

• 
  

Multiple Select

Check all of the following that are life sustaining properties of water

• High specific heat

• cohesion and adhesion

• ice is less dense than water

• water is the universal solvent

Multiple Choice

If water was not a polar molecule

• it would stick to more things.

• it would become less dense as a solid

• it would not dissolve as many things.

• cool you down as it evaporates.

Multiple Choice

Review:

Electrons are shared in a _____ bond

• ionic

• covalent

Multiple Choice

Review:

Water is a _____ molecule

• polar

• nonpolar

Poll

In terms of covalent and ionic bonding, I feel

• very comfortable. I have a good understanding of it.

• OK. I think that I understand the difference between the two.

• confused. I'm not sure what they are or what they mean.

Poll

When considering the life sustaining properties of water, I feel

• very comfortable. I understand them.

• OK. I think I understand them and will improve with more reading/notes.

• confused. I have no idea what they are referring to.

Multiple Choice

When water evaporates off of your skin, it _____ you.

• warms

• cools