Structure & Properties of Water

STRUCTURE OF WATER UNIVERSAL SOLVENT DENSITY COHESION POLAR MOLECULE SPECIFIC HEAT ADHESION CAPILLARY ACTION SURFACE TENSION BUOYANCY

O STRUCTURE OF WATER 1 molecule of water is H H O 1 molecule of water is made up of 2 hydrogen atoms bonded with 1 oxygen atom

The bond that forms water STRUCTURE OF WATER H H O The bond that forms water is a covalent bond

CHEMICAL FORMULA H2O = RIGHT H2O = WRONG 2HO = WRONG

O H 1 molecule of water

A LOT OF MOLECULES OF WATER H O H O H O H O H O H O H O H O H A LOT OF MOLECULES OF WATER O H O H O H O H O H O H O H O H O H

Millions of molecules of water make up 1 raindrop

POLAR MOLECULE _ + A molecule that has electrically charged areas. Also called a polar substance or polar compound. _ + DURACELL

NON-POLAR SUBSTANCES Non-polar substances do not have charged ends DURACELL

NON-POLAR SUBSTANCES Non-polar substances DO NOT dissolve in water. Can you think of some examples of non-polar substances? DURACELL

+ + O H -

POLAR MOLECULE The positive hydrogen ends of 1 molecule are attracted to the negative end of the oxygen of another molecule. O H O H

POLAR MOLECULE THE PROPERTIES OF: Cohesion, adhesion, specific heat, universal solvent, capillary action, surface tension ALL HAPPEN BECAUSE WATER IS A POLAR SUBSTANCE!

SURFACE TENSION

SURFACE TENSION

SURFACE TENSION

SURFACE TENSION The tightness across the surface of water that is caused by the polar molecules pulling on one another. Makes the surface act like a solid

CAPILLARY ACTION The combined force of attraction among water molecules and with the molecules of the surrounding material. Cohesion + Adhesion

CAPILLARY ACTION

COHESION Because water is a polar molecule, it is attracted to itself. Cohesion – is the attractive force between water molecules. O H O H

COHESION Water molecules like to stick to each other. Rubbing alcohol doesn’t like to stick to itself as much as water.

ADHESION Because water is a polar molecule, it is attracted to other substances. Adhesion – occurs when molecules of water are attracted to other substances.

Adhesion is going on between the windshield and the water droplet.

ADHESION

Water molecules like to stick to each other. COHESION Water molecules like to stick to each other. ADHESION Water molecules like to stick to other things.

Density of Water The density of water: Prevents water from freezing from the bottom up. Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation. Makes transition between season less abrupt.

When water reaches 0oC, water becomes locked into a crystalline lattice with each molecule bonded to to the maximum of four partners. As ice starts to melt, some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state.

SPECIFIC HEAT Specific Heat = the amount of energy needed to increase the temperature of something 1 degree C. Water has a really HIGH specific heat That means it takes a lot of energy for water to increase its temperature. This is because of the STRONG ATTRACTION between water molecules. It’s POLAR!

SPECIFIC HEAT WATER = 75°F BEACH = 200°F

UNIVERSAL SOLVENT

UNIVERSAL SOLVENT This is a nickname given to water. Water dissolves LOTS of things. Remember: SOLVENT = the thing doing the dissolving SOLUTE = the thing that dissolves away Other polar molecules can be dissolved by water.

Universal Solvent Why is water so good at dissolving things? Because water is a polar molecule and is shaped like a wedge, it is able to break up substances into smaller pieces (dissolve).