Chemical Properties of Water

A liquid over 71% of the earth A liquid over 71% of the earth

Water molecules =asymmetrical is shape with the two hydrogen molecules at one end Water molecules =asymmetrical is shape with the two hydrogen molecules at one end – Separated by 105 o when in the gaseous or liquid phase – o when ice. Polar Structure

Electronegativity of H20

Unique properties good for living things: Unique properties good for living things: – Hydrogen bonds (affects all other properties) – Adhesion and Cohesion allow it to travel up a plant, creating: °Capillary Action Properties of Water

Capillary Action Glass has polar molecules. Glass has polar molecules. Glass can hydrogen bond. Glass can hydrogen bond. Attracts the water molecules. Attracts the water molecules. Some of the pull is up. Some of the pull is up.

Meniscus Water curves up along the side. Water curves up along the side. This makes the meniscus. This makes the meniscus.

Surface Tension Water drops are round because all the molecules on the edge are pulled to the middle. Water drops are round because all the molecules on the edge are pulled to the middle.

Properties of Water Surface tension Surface tension – Cohesion between water molecules form a skin-like surface

Properties of Water Surface tension Surface tension – Can support animals like “water striders in ponds

Properties of Water High heat capacity, amount of heat needed to raise the temperature of one gram of water 1 o C. High heat capacity, amount of heat needed to raise the temperature of one gram of water 1 o C. Greater solvent power than any other substance. Greater solvent power than any other substance.

Properties of Water Stores much energy as heat Changes temperature slowly Changes temperature slowly Maintains HOMEOSTASIS Maintains HOMEOSTASIS High heat of fusion Temp at which liquid turns solid Temp at which liquid turns solid High heat of vaporization Temp at which liquid turns to gas Temp at which liquid turns to gas

Stores much energy as heat Changes temperature slowly Changes temperature slowly Maintains HOMEOSTASIS Maintains HOMEOSTASIS – Important for ocean habitat Properties of Water

Change of State

Dipole Structure Ice floats in water because all ice molecules are held in hexagons Ice floats in water because all ice molecules are held in hexagons Center is open space, making ice 8% less dense than water. Center is open space, making ice 8% less dense than water.

Dipole Structure Floating ice insulates water below, preventing freezing: critical for ocean animals Floating ice insulates water below, preventing freezing: critical for ocean animals

Maximum density: 3.98 o C Below this temp, form hexagonal polymers and decrease density Below this temp, form hexagonal polymers and decrease density Above this, molecules are energetic, move farther apart, decreasing density Above this, molecules are energetic, move farther apart, decreasing density

Solvent Properties Water dissolves salts by surrounding the atoms in the salt molecule and neutralizing the ionic bond holding the molecule together Water dissolves salts by surrounding the atoms in the salt molecule and neutralizing the ionic bond holding the molecule together

Acids, Bases & Salts Acids = compounds (or ions) that react with water to produce hydrogen ions (H + ) Acids = compounds (or ions) that react with water to produce hydrogen ions (H + ) Bases = compounds that yield the hydroxide ion (OH-) in water solutions. Bases = compounds that yield the hydroxide ion (OH-) in water solutions. Salts = ionic compounds that are generally formed by the reaction of an acid and a base: Salts = ionic compounds that are generally formed by the reaction of an acid and a base:

Measuring Acidity HYDRONIUM IONS HYDROXIDE IONS = H+ ions = OH ‑ ions = H+ ions = OH ‑ ions

Acid Formation SO 2 + H 2 O --->H 2 SO4 -2 (Sulfuric acid) SO 2 + H 2 O --->H 2 SO4 -2 (Sulfuric acid) NO 2 + H >HNO 3 - (Nitric acid) NO 2 + H >HNO 3 - (Nitric acid)

Measuring Acidity pH scale (log scale) pH scale (log scale) –normal rain water (pH of 5-6) CO 2 + H 2 O -----> HCO 3 - – pH of acid rain is between 3-4

Measuring Acidity

pH - Percent Hydronium Related to the amount of CO 2 dissolved in water Related to the amount of CO 2 dissolved in water – CO 2 combines with the water to produce carbonic acid which releases H + ions. H 2 CO > H + + HCO 3 - H 2 CO > H + + HCO 3 - CARBONIC ACIDHYDRONIUM BICARBONATE ION ION

Buffers Dissolved CO 2 in water acts as a buffer, a substance that prevents large shifts in pH. Dissolved CO 2 in water acts as a buffer, a substance that prevents large shifts in pH.

Buffer Systems CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -  H + + HCO 3 -  H + + CO 3 -2 H + + CO 3 -2 H 2 CO 3 is carbonic acid, H + is the hydronium ion HCO 3 - is the bicarbonate ion CO 3 -2 is the carbonate ion

Buffer Systems CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -  H + + HCO 3 -  H + + CO 3 -2 H + + CO 3 -2 Adding CO 2 shifts the reaction to the right and produces more H + ions making the water more acid. Adding CO 2 shifts the reaction to the right and produces more H + ions making the water more acid.

Buffer Systems CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -  H + + HCO 3 -  H + + CO 3 -2 H + + CO 3 -2 Removing CO 2 shifts the reaction to the left, combining H + ions with carbonate and bicarbonate ions reducing the acidity. Removing CO 2 shifts the reaction to the left, combining H + ions with carbonate and bicarbonate ions reducing the acidity.

Ocean Buffers

Designed by Anne F. Maben These images are for viewing only and may not be published in any form