Biology 2.1-2.4

Lesson 2.1 The Nature of Atoms and Elements Found in Living Systems (Reading)

·         Define an element based on its composition.

Only substances that cannot be broken down to any other substance by ordinary chemical means

·         Identify the subatomic particles of an atom (electrons, neutrons, and protons) and their characteristics.

Protons: Positively charged located in the nucleus

Neutron: No charge located in the nucleus

Electrons: Negatively charged located outside the nucleus

·         Define atomic number and atomic mass.

Atomic number: The number of protons in the nucleus

Atomic Mass: Sum of all protons and neutrons in the atomic molecule

·         Determine the number of neutrons, protons, and electrons in an atom given its atomic number and atomic mass.

Carbon would have 6 protons, neutrons and electrons but an atomic mass of roughly 12

·         Define cation and anion.

Cation: Positively charged ion

Anion: Negatively charged ion

·         Define isotope: Different forms of the same element with the same number of protons but different number of neutrons

·         Define valence electrons: An electron outermost energy level of an atom

·         List the important elements found in living systems.

                        Carbon Hydrogen Oxygen and Nitrogen

·         Define trace elements and identify an example.

                            Zn and I

Lesson 2.2 Chemical Bonds

·         Describe the relationship between atomic structure and chemical properties.

The chemical behavior of an atom is determined by the number and arrangement of electron in its valence shell

·         Explain the basis of the electronegativity of atoms.

Electronegativity is an atom attraction for the covalent bond

More electronegative an atom is its ability to attract to a bond

·         Predict which elements are likely to form ions.

Atoms with nearly full or nearly empty valence shells are most likely to form ions

·         Explain how molecules are formed from atoms joined by covalent bonds.

Covalent bonds form when an atom shares two or more valence electrons which will result in no net charge

·         Contrast polar and nonpolar covalent bonds.

Nonpolar covalent bonds: Electrons are shared equally

Polar Covalent bonds: Electrons are shared unequally

·         Explain how hydrogen bonding results from polar covalent bonds.

Hydrogen bonds are formed when a hydrogen atom covalently bonded to an electronegative atom like oxygen nitrogen attracts electronegative atom

·         Identify the reactants and products of a chemical reaction.

Reactants: Original molecules that undergo change

Products: new molecules resulting from the reaction

Lesson 2.3 Chemical Properties of Water

·         Relate how the structure of water leads to hydrogen bonds.

water forms hydrogen bonds because the molecule is asymmetrical and the hydrogens, which are slightly positive, are attracted to the slightly negatively charged oxygen atoms on other molecules

·         Describe water’s adhesive and cohesive properties.

Cohesion: Water molecules held together collectively by hydrogen bonds

Adhesion: Water molecules held together by other polar molecules by hydrogen bonding

·         Explain the relevance of the six emerging properties of water that are important for life.

Property 1: Water has a high specific heat capacity. Large amounts of energy is required to change the temperature of water.

Property 2: Water has high vaporization

Property 3: Solid water is less dense than liquid water

Property 4: Water is a good solvent

Property 5: Water organizes nonpolar molecules

Property 6: Water forms ions

·         Define specific heat, heat of vaporization, and evaporative cooling.

Specific heat: Is the amount of heat that must be absorbed or lost for 1g of that substance to change by 1*C

Heat vaporization: Is the amount of energy required to change 1g of a substance from a liquid to a gas

Evaporative cooling: helps stabilize temperature in organisms and bodies of water

·         Identify solvent and solute in a solution.

Solvent: The dissolving agent of a solution ex water

Solute: The substance that is dissolved ex salt

·         Differentiate between hydrophobic and hydrophilic substances.

Hydrophilic (water loving): One that has an affinity for water

Hydrophobic (water filling): One that does not have an affinity for water nonpolar molecules are polar

·         Identify the dissociated products of water (hydroxide, hydrogen, and hydronium ions).

Hydrogen ion(H+) proton

Hydronium ion (H3O+) Often represents as H+

Hydroxide ion (OH-)

Lesson 2.4 Acids and Bases

·         Differentiate between acids and bases.

Acid any substance that dissociates in water to increase the H+ concentration ranges typically falls between 1-6

Bases any substance that combines with H+ dissolved in water and lowers the [H+] ranges are 8-14

·         Relate changes in pH to changes in [H⁺].

Ph scale is logarithmic meaning that each unit charge in pH represents a 10-fold change in[H+] in

A decrease from 7-5 is 10-fold or 100 decreases in [H+]

Equation pH=-log[H]

[H+][OH-]=10*-14

·         Describe how buffers help stabilize pH.

Buffers are substances that resist changes in pH by either releasing hydrogen ions when a base is added or absorbing hydrogen ions when acidic is added