Chapter 2: Homework

Matter is composed of:

atoms

A(n) _______ acts to decrease the hydrogen ion concentration of a solution.

base

A(n) _________ acts to maintain a relatively stable concentration of hydrogen ions in a solution.

buffer

As the hydrogen ion concentration of a solution increases, the pH _______________.

decreases

The orbitals of an atom contain negatively charged particles called _________.

electrons

Substances composed of atoms that all have the same number of protons are called ____________.

elements

As the hydrogen ion concentration of a solution decreased, the pH _____________.

increases

When electrons move away from the nucleus the energy ________.

increases

In a chemical analysis of an animal tissue sample, which element would be in the least quantity?

iodine

Atoms that have gained or lost electrons and are no longer electrically neutral are called ________.

ions

If different atoms have the same number of protons but different numbers of neutrons they are called __________.

isotopes

The pH of a solution is defined as the _____________ ____________ of the hydrogen ion concentration.

negative logarithm

The amino acid glycine (C3NO2H6) is a(n):

organic molecule

Because oxygen is more electronegative than hydrogen, the water molecule is:

polar

Adhesion

- Capillary - Water readily dissolves other polar molecules - Water readily dissolves table sets (NaCl) - Paper towels readily absorb water

One of the 4 most common elements in living organisms

- Carbon (C) - Oxygen (O) - Hydrogen (H) - Nitrogen (N)

Ionic Bond

- Formed by an attraction between atoms with opposite charges. - Bond that holds NaCl together. - Involves a transfer of one or more electrons from one atom to another. - Lead to the formation of a crystal lattice rather than distinct molecules. - Weakest type of bond shown.

Cohesion

- High surface tension - Water is a liquid rather than a gas at room temperature - High specific heat - High heat of vaporization

Present in trace amounts only

- Iodine (I) - Zinc (Zn)

Not one of the 4 most common elements in living organisms, but present in greater than trace amount

- Sodium (Na) - Chloride (Cl) - Calcium (Ca) - Phosphorous (P) - Potassium (K) - Sulfur (S) - Magnesium (Mg) - Iron (Fe)

Double Covalent Bond

- The type of bond that holds a molecule of oxygen together. - Involves 2 atoms sharing 4 electrons. - The strongest type of bond shown. - Carbon dioxide is held together by this type of bond.

Single Covalent Bond

- This type of bond holds a molecule of hydrogen together. - Involves 2 atoms sharing 2 electrons. - Two chlorine atoms are held together by this bond.

Match each property of water with its effect on living organisms.

1. A wide variety of substances can move freely and interact with cells. - High solubility of ions and polar molecules 2. The temperature of living organisms is relatively stable. - High specific heat 3. Evaporation of water is often used to cool body surfaces. - High heat of vaporization 4. Lakes freeze from the top down, allowing fish and other life to survive below the surface. - Ice is less dense than liquid water 5. Nonpolar molecules tend to aggregate or organize in ways that minimize their contact with water. - Hydrophobic exclusion

Given the electronegativity of each of the following atoms, rank the bonds from most polar (number 1) to least polar (number 5). 0 = 3.5, N = 3.0, C = 2.5, H = 2.1

1. O-H 2. C-O 3. C-N 4. C-H 5. C-C

4. Household ammonia has a pH of 11, therefore its H+ concentration is ___________ times less than a solution with a pH of 7.

10,000

1. Beer has a pH of 3, therefore its H+ concentration is _____ times greater than a solution with a pH of 5.

100

2. Black coffee has a pH of 5, therefore its H+ concentration is ___________ times greater than a solution with a pH of 10.

100,000

What is the atomic mass for a carbon atom that has 7 neutrons in its nucleus?

13

___________ has an atomic mass of 28.

Aluminum

________ has an atomic mass of 41.

Calcium

According to most car mechanics, plain water is the best coolant to use in an engine provided the engine is not being exposes to freezing temperatures. If the car is subject to freezing temperatures then a mixture of water and ethylene glycol (antifreeze) is recommended but it does not cool as efficiently as plain water. Why would ethylene glycol reduce the cooling efficiency of water?

Ethylene glycol has a lower capacity than water.

Salt is often used to melt ice on roads during the winter because it lowers the freezing/melting point of water. When salt dissolves in water, individual Na+ and Cl- ions break away from the salt lattice and become surrounded by water molecules. Why would this cause ice to melt?

Hydrogen bonds are broken, and the salt ions interfere with interactions between H and O. As a result, it is more difficult for water molecules to bond and form ice.

Proteins are three dimensional molecules made of strands of amino acid (imagine a ball of string). There are 20 different amino acids used in proteins found in living organisms. Some of these amino acids are polar and others are non-polar. Where would a series of non-polar amino acids most likely be located in a protein that is found in the cytosol of an animal cell?

In the interior of the protein.

Potassium has ___ valence electron.

1

3. Urine has a pH of 6, therefore its H+ concentration is _______ times greater than a solution with a pH of 9.

1,000

Sodium has ___ protons.

11

Bromine has ____ protons.

35

How many hydrogen bonds can a water molecule form?

4

A(n) ________ acts to increase the hydrogen ion concentration of a solution.

acid

As the pH of a solution increased, the concentration of ___________ ions increases.

hydroxide

The nucleus of an atom always contains one or more ___________.

protons

The atomic number of carbon-13 is ________.

six

The atomic mass of carbon-13 is __________.

thirteen