Chapter 3 – Water and Life
1. With the use of a diagram, explain why water molecules are:
Water is polar because opposite ends of the molecule have opposite charges
b. capable of hydrogen bonding with 4 neighboring water molecules
Because hydrogen has a partial positive charge and oxygen has a partial negative charge, thus being able to bond to other water molecules in four places
2. List four characteristics of water that are emergent properties resulting from hydrogen bonding.
Moderation of Temperature
Insulation of Bodies of Water by Floating Ice
Solvent of Life
3. Define cohesion and adhesion. Explain how water’s cohesion and adhesion contribute to the movement of water from the roots to the leaves of a tree.
Cohesion is important in plants as it helps for water to move up the plant, and adhesion keeps the water from falling due to gravity
4. Explain the following observations by referring to the properties of water:
Coastal areas have milder climates than adjacent inland areas.
Water has the ability to cool the temperature when near land
Ocean temperatures fluctuate much less than air temperatures on land.
Water has a high specific heat
Insects like water striders can walk on the surface of a pond without breaking the surface.
Density and Surface tension
If you slightly overfill a water glass, the water will form a convex surface above the top of the glass.
If you place a paper towel so that it touches spilled water, the towel will draw in the water.
Ice floats on water.
Ice is not as dense as water
Humans sweat and dogs pant to cool themselves on hot days.
5. Name the products of the dissociation of water and give their concentration in pure water.
Hydronium Ion (H30) and Hydroxide Ion (OH)
6. Define acid, base, and pH.
Acid – a substance that increases the hydrogen ion concentration of a solution
Base – a substance that reduces the hydrogen ion concentration
pH – the negative logarithm of the hydrogen ion concentration.
1. Explain how carbon’s electron configuration accounts for its ability to form large, complex, and diverse organic molecules.
Carbon’s four valence electrons and it’s need to satisfy the octet rule allows it to form four covalent bonds with other atoms including other carbon atoms. This property along with its small size allows carbon to form long chains and other large molecules with carbon backbones.
2. Describe how carbon skeletons may vary, and explain how this variation contributes to the diversity and complexity of organic molecules.
Carbon skeletons vary in length and may be straight, branched, or arranged in closed rings. Some skeletons have double bonds, which vary in number and location. Such variation in carbon skeletons is one important source of molecular complexity and diversity that characterize living mater.
3. Describe the basic structure of a hydrocarbon and explain why these molecules are hydrophobic.
Hydrocarbons are organic molecules consisting only of carbon and hydrogen, these molecules are hydrophobic because of the non-polar bonds of hydrocarbons and the inability of polar dissolving non-polar compounds.
4. Name the major functional groups found in organic molecules. Describe the basic
structure of each functional group and outline the chemical properties of the organic molecules in which they occur.
Structure – a hydrogen atom bonded to an oxygen atom, which is in turn bonded to the carbon skeleton of an organic molecule. (not hydroxide ion OH-)
Functional Properties – Polar (e– negative oxygen), attracts water molecules helping dissolve organic compounds such as sugars.
Structure – carbon atom joined to an oxygen atom by a double bond
Functional Properties – Ketones if group is within carbon skeleton and Aldehydes if group is at the end of skeleton.
Both are usually isomers.
Structure – oxygen atom double bonded to carbon atom that is bonded to a hydroxyl group.
Functional Properties – acidic properties (hydrogen ions), covalent bond between oxygen and hydrogen tends to dissociate reversibly.
Structure – nitrogen atom bonded to two hydrogen atoms and carbon skeleton
Functional Properties – acts as a base, ionized with a charge of 1+ (under cellular conditions)
Structure – sulfur atom bonded to hydrogen atom
Functional Properties – two sulfhydryl groups can interact to stabilize protein structure
Structure – Phosphorus atom is bonded to four oxygen atoms, one is bonded to carbon skeleton and two carry negative charges (–OPO32–).
Functional Properties – makes the molecule of which it is a part an anion, and can transfer energy between organic molecules