AP Biology Chapter 2

AMU

Atomic Mass Unit; protons and neutrons assigned one AMU each, electrons so small their AMU is zero.

electrons

negatively charged particles

solvent

substance that dissolves

Identify some common acidic and basic substances.

Acidic: Vinegar Lemon juice tomatoes coffee Carbonic acid Basic: Sodium Carbonate (washing soda) Baking soda Milk of Magnesia Antacid tablets Ammonia

The pH scale

On the pH scale, 7 is neutral (like water, sugar, and table salt). Anything below 7 is acidic and anything above is basic. The scale ranges from 0 to 14, 0 being extremely acidic and 14 being very basic.

Elements

a substance that cannot be broken down to a simpler substance with different properties.

Isotopes

atoms of the same element that differ in the number of neutrons. Have the same number of protons, different atomic masses.

solution

complete mixture

Periodic Table

developed by Dmitri Mendeleev, a way to group the elements (and thus atoms) according to certain chemical and physical characteristics.

neutrons

neutrally charged particles

valence shell

outermost shell

Determine pH from H+ or OH- concentration.

pH = - log [H+] [H+] = 10-pH or antilog (- pH) pOH = - log [OH-] [OH-] = 10-pOH or antilog (-pOH)

protons

positively charged particles

solute

substance that is dissolved

List and analyze the properties of water.

1. Hydrogen bonding -water molecules cling together. -responsible for water being a liquid at normal temperatures 2. A High Heat Capacity -water requires a calorie of energy to raise the temperature one degree Celsius, other covalently bonded liquids require half this. -because of the many hydrogen bonds that link water molecules, water can absorb heat without a great change in temperature. 3. A High Heat of Evaporation -hydrogen bonds must be broken before water can boil so converting 1 gram of the hottest water to gas takes 540 calories. 4. Solvent-due to its polarity, water facilitates chemical reactions both inside and outside living systems. -it dissolves a great number of substances 5. Cohesive and Adhesive-Cohesion is the ability of water molecules to cling to each other due to hydrogen bonding. Because of this, water exists as a liquid in the conditions present at the Earth's surface. -Adhesion is the ability of water molecules to cling to other polar surfaces as a result of water's polarity. 6. Frozen Water (Ice) is Less Dense Than Liquid Water -water becomes most dense at 4 C but the molecules are still moving around. At temperatures below 4C only vibrational movement occurs and hydrogen bonding becomes more rigid but also more open. This means that water expands as it reaches 0C and freezes. Ice is therefore less dense than liquid water and floats on it.

Analyze how buffers prevent large pH changes in solutions.

A buffer is a chemical or combination of chemicals that keeps pH within normal limits. Buffers, among other things, keep the pH of blood around 7.4. Buffers keep the pH within normal limits because they are chemicals that take up excess H+ ions or OH- ions.

What happens if the pH of blood is changed?

If blood pH drops to 7, acidosis results. If blood pH rises to 7.8, alkalosis results.

Describe how elements are combined into molecules and compounds.

Elements can be combined to form molecules and compounds through different bonds. 1. Ionic Bonding (donation): Electron transfer that causes a charge imbalance in each atom (thus the name "ionic" for ion) Held together by a strong attraction between negatively and positively charged ions. 2. Covalent Bonds (joint sharing): Bonding when two atoms share electrons in such a way that each atom has an octet of electrons on the outer shell. {2 electrons in the case of Hydrogen} <--nonpolar and polar covalent bonds→ Nonpolar- when the sharing of electrons between two atoms is equal. If one atom is better able to attract electrons than the other atom, it is more electronegative. 3. Hydrogen Bonding: (especially water, but not unique to it) more easily broken than other bonds, the attraction of a slightly positive hydrogen to a slightly negative atom in the vicinity, a polar covalent bond

Determine how electrons are configured around a nucleus.

John Dalton developed the atomic theory, which stated that elements consisted of tiny particles called atoms. The concept has changed greatly from that time. If an atom could be drawn the size of a football field, the nucleus would be like a gum-ball in the center and the electrons tiny specks whirling around the upper stands.

What makes up the inside of an atom?

Most of an atom is empty space.

Describe how protons, neutrons, and electrons relate to atomic structure.

Protons and neutrons are located in the nucleus of an atom, while electrons move around it. The atomic number of an atom represents the number of protons located in its nucleus. (Since elements are neutrally charged, the number of protons are equivalent to the number of electrons. Thus, the atomic number also tells the number of electrons.) The mass number of an atom is the sum of protons and neutrons in the nucleus. The atomic mass is the average of the AMU for all the isotopes of that atom. [To determine the number of neutrons, subtract the number of protons from the atomic mass.]

Analyze the relationships between atomic number and mass number using the Periodic Table.

The atomic number of every atom in a period by one from left to right. All atoms in a group share the same binding characteristics

Describe how water associates with other molecules in solution.

The negative ends of water molecules are attracted to slightly positive atoms and the positive ends of water molecules are attracted to slightly negative atoms. This attraction causes the slightly positive and negative ions to dissociate.

How do variations in an atomic nucleus account for its physical properties?

The number of protons inside the nucleus decides how many electrons will move around the atom. The groups of the periodic table denote how many electrons will be on the valence shell.

Polar

when electrons are not shared equally