Properties of Water

Chapter 2

Water: Adhesion Property

Adhesion: an attraction between molecules of different substances Capillary action – water tends to climb

up straws, or similar (glass) Meniscus- water makes a curve when

sitting in a graduated cylinder- (glass) Wet jeans

Mini-lab: Capillary Action

Place the tiny tube in the colored water and watch it climb…

Does it end up lower or higher than the outside fluid level?

Can you see the meniscus in the graduated cylinder?

Water: Cohesion Property

Cohesion: attraction between molecules of the same substance Insects can walk on water Water forms droplets on certain

surfaces (glass, copper, paraffin) Surface tension

Mini-Lab: Quicker Picker upper

Pour 5 mL of water on your desk. Take the papertowel and place only the very end in the pool of water.

Once it stops climbing, measure how far the water climbed.

Wipe up the desk

Mini-Lab :surface tension

Take a small paperclip and float it in a beaker of water

What is the trick to doing this?

Mini-Lab: cohesion

How many drops of water can you fit on a penny?

What shape does the water make? Why does the water eventually

spill over?

Polar?

Water is polar, which means the atoms have slight charges, which makes it attract itself and other substances, too. That bond is a hydrogen bond and it

is really weak

WHY is water polar? Because of the 8 protons in the nucleus, the Oxygen has a stronger attraction for electrons than hydrogen (in other words they share unequally)

Other polar compounds? NH3 ammonia HF hyrdogen fluroride

Water is more polar than any other compound- so it will tend to dissolve ionic compunds,

and other polar substances very well Alcohol is also polar,

so it does mix with water, but its has a lower degree of polarity,

so it won’t dissolve some things that water can

OIL- is non-polar

Why does ice float? Why is that soooooo important to our

planet?

The story:

Alcohol doesn’t freeze at the same temperature as water…so why did I get in so much trouble?!

Water is an exception to many rules

It freezes from the top down It becomes less dense when frozen solid

Because the hydrogen bond pattern created “pockets of open space” making it less dense or lighter…see bubbles?? In ice??

It ‘s boiling point is too high for its size It’s freezing point is too low for its size

The normal pattern for most compounds is that as the temperature of the liquid increases, the density decreases as the molecules spread out from each other. As the temperature decreases, the density increases as the molecules become more closely packed. This pattern does not hold true for ice as the exact opposite occurs.

In liquid water each molecule is hydrogen bonded to approximately 3.4 other water molecules. In ice each each molecule is hydrogen bonded to 4 other molecules.

The End…..