Can you die from drinking too much water? http://video.about.com/chemistry/Can-You-Drink-Too-Much-Water.htm Take notes from this video

WATER AND SOLUTIONS Page 39-44 BIOLOGY WATER AND SOLUTIONS Page 39-44

BY THE END OF THIS LECTURE, YOU WILL BE ABLE TO: LECTURE OBJECTIVES BY THE END OF THIS LECTURE, YOU WILL BE ABLE TO: 1. Explain how water’s polar nature affects its ability to dissolve substances. 2. Outline the relationship between hydrogen bonding and the different properties of water.

WATER! Water is essential to life because of its structure The water molecule is one oxygen atom and two hydrogen atoms that are bonded COVALENTLY (they share electrons) See pictures on page 39 of text Explain the structure of an atom (protons, neutrons, electrons) and that bonds hold atoms together.

POLARITY The total charge on a water molecule is NEUTRAL (no charge) BUT the charge is not the same on both sides Water is called a POLAR molecule because the charge is different on 2 sides

SOLUBILITY OF WATER OPPOSITES ATTRACT! Because a water molecule is POLAR, other polar molecules will dissolve easily in water OPPOSITES ATTRACT! Explain that “-” side of water molecules are surrounding Na+ and that “+” side of water molecules are surrounding Cl-

Because water is POLAR water molecules stick to themselves HYDROGEN BONDING Because water is POLAR water molecules stick to themselves Water molecules are held to each other by HYDROGEN BONDS These bonds form, break, and reform A LOT

1st PROPERTY OF WATER: Water molecules sticking to each other is called COHESION Water molecules sticking to something else (like glass) is called ADHESION

TEMPERATURE MODERATION 2nd PROPERTY OF WATER: TEMPERATURE MODERATION Water has a HIGH HEAT CAPACITY, which means it can absorb or release a lot of energy without a big change in temperature The temperature of water goes up only after all the hydrogen bonds are broken

Examples: Example: The oceans stabilize global temperatures Example: Organisms can keep their cells (that are mostly water) the same temp. even though the outside temp. changes Example: Sweating water which releases body heat

3rd PROPERTY OF WATER: DENSITY OF ICE: Because the hydrogen bonds form at a certain angle there is a lot of space between molecules when frozen So, ice (which is a SOLID) is LESS dense than water (which is a LIQUID) Bodies of water freeze from top down, allowing life to exist below icy surface

REVIEW: Explain how water’s polar nature affects its ability to dissolve substances: Outline the relationship between hydrogen bonding and the different properties of water: