Water

● There is the same amount of water on

Earth as there was when the Earth was

formed. The water from your faucet could

contain molecules that dinosaurs drank.

● Nearly 97% of the world’s water is salty or

otherwise undrinkable. Another 2% is

locked in ice caps and glaciers. That

leaves just 1% for all of humanity’s needs

— all its agricultural, residential,

manufacturing, community, and personal

needs.http://water.epa.gov/learn/kids/drinkingwater/waterfactsoflife.cfm

Water Facts

● Water regulates the Earth’s temperature. It

also regulates the temperature of the

human body, carries nutrients and oxygen

to cells, cushions joints, protects organs

and tissues, and removes wastes.

● 75% of the human brain is water and 75%

of a living tree is water.

● A person can live about a month without

food, but only about a week without water.

● Water expands by 9% when it freezes.

Frozen water (ice) is lighter than water,

which is why ice it floats in water.http://water.epa.gov/learn/kids/drinkingwater/waterfactsoflife.cfm

Water

•Water is a compound•Formula

– H2O (2 Hydrogen and 1 Oxygen)

Why is water unique?

• Hydrogen Bonds-Polarity, High Specific heat, cohesion, adhesion

Polarity

•Polarity allows water to be the perfect solvent– Water can dissolve many things– No other liquid can come close to being

able to dissolve as many thing as water can

– Because of this, water is nearly always carrying something else along with it

Hydrogen bonds

•High specific heat- resists changes in temperature

•Cohesion- water sticks to itself causing surface tension

•Adhesion- water sticks to other things, meniscus, capillary action

•Capillarity- water travels upward through small tubes due to adhesion and cohesion

Other Special Qualities

•Water is the only naturally occurring compound on Earth that can be found in all three physical states

•When water freezes it floats– Extremely unique property– Contracts as it cools until it hits 4° C

when it expands again

Why does Water Expand into Ice?

Diffusion

•Diffusion-The movement of particles from areas of high concentration to areas of low concentration

•Examples– Perfume bottle– Cookies in the oven– Kool-Aid

What diffusion looks like

•http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Solutions•Mixture- a blend of substances that is

not equal throughout (heterogeneous)

•Solvent + Solute = Solution•Solvent- Liquid capable of dissolving

other substances•Solute- substance being dissolved•Solution- a mixture of substances

that is equal throughout (homogeneous)

Mixtures

Solutions

+ =

Solvent

Solution

Solute

Osmosis

• Osmosis-Diffusion of water molecules, usually involving a semi-permeable membrane

• Concentration Gradient- difference in concentration from one side of membrane to the other

• Equilibrium-the same everywhere• Remember water always moves from

areas of high water concentration to areas of low water concentration

Osmosis

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

The tonics of life

• Isotonic-Concentration of solutes is the same in solution and cell.

•Hypertonic-Concentration of solutes is higher in the solution.

•Hypotonic-Concentration of solutes is lower in the solution.