1. Science Starter 9/23/15: Hand in HW (States of Matter Webquest)
What would be the effect on the properties of water molecules if oxygen and hydrogen had equal electronegativity?

2. Science Starter 9/22/15
With the person sitting next to you, think about the answer to this question:
If you had a glass of water filled TO THE BRIM with ice and water, once the ice melts, will the water overflow? Explain why or why not.

3. Notes- Water

4. Water is Amazing!! water covers 3/4 of Earth’s surface
water is the main reason why life exists on Earth!
water has many unique properties that allow it to be supportive of life on Earth

5. Polarity of Water
Water molecule: two hydrogen atoms joined to an oxygen atoms via polar covalent bonding
Result= a molecule that has a slightly negative end (the O side) and a slightly positive end (the H side)= Polar Molecule

6. Polarity of Water
When multiple water molecules are near each other, they form hydrogen bonds with each other
the (+) H-side is attracted to the (-) O side
creates a sticky molecule

7. Properties of Water 1. cohesion and adhesion 2. good solvent
molecules dissolve in water
3. lower density as a solid (ice floats!)
4. high specific heat
water stores heat
5. high heat of vaporization
heats & cools slowly

8. 1. Cohesion & Adhesion Cohesion Adhesion
hydrogen bonding between water molecules
water is “sticky”
results in surface tension
Adhesion
bonding between water molecules and a different substance
meniscus on a graduated cylinder
water climbs up paper towel

9. 2. Water is the universal solvent
Since water is polar, it dissolves other polar substances easily
“like dissolves like”
The solvent dissolves the solute to form a solution

10. Check-In: different molecules#2
different molecules
red arrows indicate the direction electrons are being pulled
with your seat partner, try to figure out which molecules are POLAR and which are NON POLAR #5 #4 #3

11. 3. Lower density as a solid
Pretty much all substances are more dense as solids..
But, ice floats!
Hydrogen bonds form a crystal with space in between each molecule
Ice has fewer molecules than an equal volume of water= less dense

12. “Ice floats” has many good effects:
If ice sank, eventually all ponds, lakes, and even the ocean would freeze solid!
surface ice insulates the water underneath it
allows life to continue in winter
seasonal turnover of nutrients in lakes
cold sinking water flushes up nutrients

13. 4. High specific heat Water resists changing temperature
takes a long time to heat up
takes a long time to cool down
water keeps Earth’s temperatures moderate (especially when you live near a large body of water!)
LONG ISLAND, NY

14. 5. High heat of vaporization
water requires a large amount of heat in order to change from liquid to vapor
evaporative cooling- as liquid evaporates, the liquid that remains behind cools down (the “hottest” molecules leave)
organisms rely on evaporative cooling to maintain body temperatures!

16. pH review.. Water ionizes: H+ splits off from OH-
if [H+] = [OH-], water is neutral, pH=7
if [H+] > [OH-], water is acidic, pH under 7
if [H+] < [OH-], water is basic, pH over 7
H2O H+ + OH–

17. pH scale
if you go up or down by ONE on pH scale, it is actually 10x more or less H+ ions
> > 14
10–1
H+ Ion
Concentration
Examples of Solutions
Stomach acid, Lemon juice 1 pH
100
Hydrochloric acid
10–2 2
10–3
Vinegar, cola, beer 3
10–4
Tomatoes 4
10–5
Black coffee, Rainwater 5
10–6
Urine, Saliva 6
10–7
Pure water, Blood 7
10–8
Seawater 8
10–9
Baking soda 9
10–10
Great Salt Lake 10
10–11
Household ammonia 11
10–12
Household bleach 12
10–13
Oven cleaner 13
10–14
Sodium hydroxide 14
MOST ACIDIC
NEUTRAL
MOST BASIC