Chapter 2 - Nature of Molecules & Water

Define Atom.

Smallest unit of matter

Which subatomic particles does an atom consist of?

Protons, Neutrons, and Electrons

What are the properties of Protons?

• Positive charge

• located in nucleus

• determines element

What are the properties of Neutrons?

• No charge

• Located in nucleus

• Determines atomic mass and isotopes

What are the properties of Electrons?

• Negative charge

• orbits nucleus in shells

• weighs much less than other subatomic particle

• determines chemical behavior of element

Define Atomic Number

Number of protons determines the element

Define Atomic Mass

Sum of protons + neutrons

Define Isotope

forms of the same element that have different atomic masses/different # of neutrons

Define Element

Pure substance made of only one type of atom; cannot be broken down

How many naturally occurring elements are there?

92

How many elements are essential to life?

25

What are the 4 most abundant elements?

C, H, O, & N

What percentage of body mass is just the 4 most abundant elements?

96%

Define Chemical Reaction

the formation or breaking of chemical bonds

What does conservation of matter mean in terms of a chemical reaction?

Same # of atoms before and after the rxn

What are the 3 factors that chemical reactions are influenced by?

• Temperature

• Reactant & Product Concentrations

• Catalysts

Describe how temperature influences chemical rxns.

• heat increases rxn rates

• cold decreases rxn rates

Describe how Reactant & Product Concentrations influences chemical rxns.

• High reactant concentration increases rxn rates

• High product concentration decreases rxn rates

  • but increases rxn rates for reverse reactions (breaking products into smaller parts)

Describe how catalysts influences chemical rxns.

• presence of a catalyst increases reaction rates

Most biological reactions are ____.

Reversible

Define Coupled Redox Reaction

where both oxidation and reduction occur at the same time

Define Oxidation

Loss of elections

Define Reduction

Gain of electrons

Why do coupled redox reactions happen?

Because atoms seek their most stable state

• an electron is lost by one atom and is gained by another to become more stable

What is an example of a coupled redox reaction?

Cellular respiration:

• glucose is oxidized and O_2 is reduced

Define the Octet Rule

elements tend to bond so that each atom has 8 electrons in its valence shell

Define Valence

The outermost electrons and outermost electron shell

How many elements are found in living organisms in more than trace amounts?

12

What are the 12 elements found in living organisms in more than trace amounts?

oxygen, carbon, hydrogen, nitrogen, sodium, chlorine, calcium, phosphorus, potassium, sulfur, iron, & magnesium

Define Organic Compound

compounds of carbon

What does Carbon most easily bond to?

Nitrogen, oxygen, & hydrogen

Define Ionic Bond

atoms with opposite charges attract; complete transfer of valence electrons between atoms

What can Ionic Bonds form?

crystals

What is an example of an Ionic bond?

Na+ + Cl- = NaCl

Define Covalent bond

when 2 atoms share one or more pairs of electrons

What are the two types of covalent bonds?

Polar & Nonpolar

Define Polar Covalent Bond

equal sharing of electrons between atoms

Define Nonpolar covalent bond

Inequal sharing of electrons between atoms

What kind of bonds can covalent bonds for IN ORDER?

Single < double < triple

Why do covalent bonds form stable bonds?

1.) Molecules have no net charge

2.) Octet rule is satisfied

3.) no unpaired electrons

Define Hydrogen Bond

weak interactions between a partially positive hydrogen in one molecule & partially negative oxygen in another molecule

A hydrogen bond is also a ___ ___ bond.

Polar Covalent

Describe the structure of a water molecule.

Two positive hydrogen atoms connected to a negative oxygen molecule

How do polar bonds react to water?

They are hydrophilic, soluble, & attracted to water

How do nonpolar bonds react to water?

They are hydrophobic, insoluble, clump up, and repel water

Water molecules are both ____ and ____.

Cohesive , Adhesive

Define Cohesive

Tendency for water molecules to adhere to one another due to hydrogen bonding

Define adhesive

polarity of water molecules causes them to be attracted to other polar molecules

What are the properties of water?

1.) High specific heat helps maintain temperature

2.) High heat of vaporization facilitates cooling

3.) Solid water is less dense and liquid water

4.) Polar molecules are soluble in water due to its polarity

5.) Water organizes nonpolar molecules

6.) Water can form ions