2.2 Properties of Water

The Water Molecule Water is the only liquid that expands when it freezes It is a neutral molecule like all others, but has something called polarity

The Mickey Mouse Molecule! Hydrogen Hydrogen Oxygen

O STRUCTURE OF WATER H H 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

Millions of molecules of water make up 1 raindrop

Polarity Because oxygen has 8 protons in the nucleus and hydrogen only has 1, it has a much higher attraction to the electrons This causes the shared electrons to be closer to the oxygen nucleus The above cause the H to have a slight positive charge and the O to have a slightly negative It is now a Polar Molecule

+ + 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!

Hydrogen Bonding

Cohesion Cohesion is the property of water that causes it to be attracted to itself. http://www.realeyz.com/photo/macro/photos/leaf_drops.jpg

Surface Tension Surface tension measures the strength of water molecules attracting to one another. This property allows insects to walk on the surface of water and the creation of waves. 1

Surface Tension Surface tension is the name we give to the cohesion of water molecules at the surface of a body of water

Water strider

Adhesion Attraction between molecules of different substances Ex: glass and water Capillarity Water molecules will “tow” each other along when in a thin glass tube. http://staff.um.edu.mt/rlib1/sm/wpe32.jpg

Solutions and Suspensions Mixture – material composed of two or more elements or compounds Solutions – components are easily distributed throughout the solution (salt and water) Solute – substance dissolved Solvent – substance in which substance dissolves Water is universal solvent Suspensions – mixture of water and nondissolved material

Suspension Solution

pH Scale Indicates the number of H+ ions Acid – a solution that contains excess H+ ions Base – a solution that contains excess OH- ions Buffer – weak acids and bases that can react with strong acids or bases to prevent sharp, sudden changes in pH