Properties of Water

Hydrogen Bonds

The polarity of

water leads to the

formation of

Hydrogen bonds.……………………………………………………………………………….

These bonds

account for the

sticking together of

water molecules

and the surface

tension.

Properties of Water

Properties of Water

Covalent bonding

Polar covalent bond ≡ unequal sharing of electrons

A great example of a molecule with polar covalent

bonds is water.

Why is water considered polar?

What is a partial positive and partial negative

charge?

Covalent bonding vs. Hydrogen bonding

Covalent

Bond

Hydrogen

Bond

Properties of Water

Chemistry Of Water

Solid water (ice) is less

dense than liquid water

The shape of water molecule (104.5°)

causes ice to float.

Properties of Water

Chemistry of Water

Water has high specific heat. A lot of heat energy has to be added into water, in

order to change the temperature.

Water is a good solvent. It can dissolve a lot of things Hydrophilic ≡ water lover (salt); polar

Hydrophobic ≡ afraid of water (oil); non-polar

Properties of Water

Chemistry of Water

Water molecules are also cohesiveand adhesive.

Cohesion ≡ When it sticks together with itself.

It is apparent because water flows freely, yet water molecules do not separate from each other.

Adhesion ≡ When it sticks to a different surface.

Because water is polar it will “stick to” (adhere) to other polar surfaces such as in tubular vessels (plant roots & stems, blood vessels, etc…)

Properties of Water

Capillary Action

Because water has both adhesive

and cohesive properties, capillary

action is present.

Capillary Action ≡ Water is attracted to some

other material and then through cohesion, other

water molecules move too as a result of the

original adhesion.

Ex: Think water in a straw

Ex: Water moves through trees this way

Properties of Water

In order to raise the temperature

of water, the average molecular

speed has to increase.

It takes much more energy to

raise the temperature of water

compared to other solvents

because hydrogen bonds hold

the water molecules together!

Water has a high heat capacity.

Specific Heat ≡ is the amount of

heat per unit mass required to

raise the temperature by one

degree Celsius.

High Heat

Capacity

Properties of Water

Water is the solvent of Life!

Example: Ice Tea – water is the solvent

… tea and sugar the solutes

Universal Solvent

Properties of Water

Solutions ≡ a liquid, usually water, in which something is dissolved

Solvents ≡ a substance that dissolves another to form a solution

Solutes ≡ the substance dissolved in a given solution

Properties of Water

Mixtures ≡ an combination of two or

more substances that are not

chemically united and that exist in no

fixed proportion to each other

Suspensions ≡ the state in which the

particles of a substance are mixed with

a fluid but are undissolved

Properties of Water

DensityWater is less dense as a solid!

This is because the hydrogen bonds are stable in ice –

each molecule of water is bound to four of its

neighbors.

Liquid – water molecules

are constantly bonding and

rebonding – space is always

changing

Properties of Water

Solid – water molecules

are bonded together –

space between fixed

So, can you name all of the properties of water?

1. Adhesion

2. Cohesion

3. Capillary action

4. High surface tension

5. Holds heat to regulate temperature

(High heat capacity)

6. Less dense as a solid than a liquid

Properties of Water

Acids and Bases

Their strength is compared using pH scale

Ranges from 0 – 14

Logarithmic Scale (gets 10x bigger/smaller)

Acid ≡ donates hydrogen ions (H+) when added to

aqueous (water) solutions Ranges from pH 0-6.9

Base ≡ breaks up into hydroxide (OH-) ions and

another compound when placed in an aqueous

solution Ranges from pH 7.1 – 14

Distilled water is pH 7.0 or neutral. Why?

H2O H+ + OH-

Properties of Water

pH pH scale is used to

indicate the acidity or basicity (alkalinity) of a solution.

A pH value is the H+

concentration of a solution.

It ranges from

0 – 14.

pH 7 = neutral

pH <7 = acid

pH >7 = base

Properties of Water

Properties of Water

Properties of Water

Ac

ids

an

d B

ase

s

BuffersBuffer ≡ a chemical or a combination of

chemicals that keeps pH within normal limits.

They resist pH changes because they can take up excess H+ & OH-

They are helpful to the human body because they help it maintain homeostasis (a healthy balance)

Properties of Water

Buffers ≡ compounds used to maintain a constant

pH within a system

Properties of Water

Acids and Bases

Cause and Effect

Properties of Water

Making Biological Molecules

Condensation Reaction

Hydrolysis Reaction

and H2O

H2O

Properties of Water