Fig. 2-10a, p. 28

Electrons spend more time orbiting the oxygen nucleus than the two hydrogen nuclei, leaving the oxygen more neg charged and the hydrogen more pos charge. Therefore, the entire molecule is "Polar", that is with one end slightly positive and one end slightly negative.

This weak electrical attraction is called a "hydrogen bond".

Fig. 2-10b, p. 28

B Many hydrogen bonds (dashed lines) that form and break rapidly keep water molecules clustered together in liquid water.

Fig. 2-10c, p. 28

C Below 0°C (32°F), the hydrogen bonds hold water molecules rigidly in the three-dimensional lattice of ice. The molecules are less densely packed in ice than in liquid water, so ice floats on water.

Fig. 2-11, p. 29

Mixtures

• Most matter exists as mixtures– Two or more components physically

intermixed• Three types of mixtures

– Solutions– Colloids– Suspensions

Solutions

• Homogeneous mixtures• Usually transparent, e.g., atmospheric air

or seawater – Solvent

• Present in greatest amount, usually a liquid– Solute(s)

• Present in smaller amounts

Colloids and Suspensions• Colloids (emulsions)

– Heterogeneous translucent mixtures, e.g., cytosol

– Large solute particles that do not settle out– Undergo sol-gel transformations

• Suspensions:– Heterogeneous mixtures, e.g., blood– Large visible solutes tend to settle out

Mixtures vs. Compounds• Mixtures

– No chemical bonding between components – Can be separated physically, such as by

straining or filtering– Heterogeneous or homogeneous

• Compounds– Can be separated only by breaking bonds– All are homogeneous

Specific heat (calorie) is defined as the amount of heat energy required to raise the temp of 1gm 1 degree C. The specific heat of liquid water is 1.0 calories while it is 0.5 calories for ice. To change from ice at 0 degrees C to water at 0 degrees C requires an additional 80 calories (the heat of fusion or melting). It now takes 100 calories to heat the water from 0 degrees C to 100 degrees C. To change from liquid to water vapor at 100 degrees C requires an additional 540 calories. This is called the heat of evaporation or condensation. It explains why it seems to take so long to boil water on the stove when it seems about to boil.

pH = -log10 [H+]

History of the pH Scale ...in 1909, the Danish scientist Soren P.L. Sörenson discussed the inadequacy of measuring acidity of a solution. The amount of acid would not be a true measure of its dissociation. Sörenson proposed the degree of acidity be rationally measured by hydrogen ion concentration and proposed the pH scale for expressing the hydrogen ion concentration.Sörenson was involved in work testing the acidity of beer and the pH symbol rooted in the French "pouvoir hydrogene" (power of hydrogen).

p. 30

p. 30

Fig. 2-13, p. 30

0 — 100 battery acid

1— 10–1 gastric fluid

2 — 10–2 acid rainlemon juicecola

3 — 10–3

orange juicetomatoes, wine

vinegar

mor

e ac

idic

4 — 10–4 bananasbeer

5 — 10–5coffeebread

urine, tea, typical rain6 — 10–6 corn

buttermilk

7 — 10–7 pure waterblood, tears

8 — 10–8 seawateregg white

baking soda9 — 10–9 phosphate detergents

Tums10 — 10–10 hand soap

milk of magnesia

toothpaste

11— 10–11

household ammonia

mor

e ba

sic

10–12hair remover12 —bleach

13 — 10–13oven cleaner

14 — 10–14 drain cleaner

Fig. 2-9, p. 27