Chapter 2: The Chemistry of Life Flashcards
What is comprised of matter?
Any substance in the universe that has mass and occupies space
What does matter exist as?
Solid, Liquid, or Gas
What is matter made up of?
Atoms
What happens when you get enough of the same atom together?
You have an element
What is at the core of all atoms?
A nucleus
How many subatomic particles are nucleus’ comprised of?
2
Protons and Neutrons
What are protons?
Positively charged and 1 mass unit
What are Neutrons?
No associated charge and 1 mass unit
What orbits the nucleus?
Electrons, which are negatively charged and almost zero mass
What is the Atomic Mass?
The number of protons + Number of neutrons
What is the Atomic Number?
Number of protons, which determines the element
What do electrons determine?
They determine the chemical behavior of atoms, as they are associated with energy
What energy of position does electrons have?
Potential energy
What do electrons occupy?
Energy levels, which are also known as electron shells, of an atom, which are complex, 3-D volumes of space called orbitals
What is the purpose of orbitals?
Orbitals are where electrons are most likely to be found
Atoms tend to be more reactive when they have
a) complete electron orbitals
b) incomplete electron orbitals
b) incomplete electron orbitals
What will atoms do in order to completely fill their outermost electron shell?
Atoms will lose, gain, or share electrons
These actions are the basis of chemical bonding
What happens when electrons move to a lower energy level, closer to the nucleus?
Energy is released
What happens when electrons move further away from the nucleus?
Energy is required - intake of energy
What are ions?
Atoms that have gained or lost one or more electrons
What are isotopes?
Atoms that have the same number of protons but DIFFERENT numbers of neutrons
What occurs when isotopes are unstable?
They break up into particles with lower atomic numbers (protons)
Known as radioactive decay
What are some uses of radioactive isotopes?
Dating fossils
Medical procedures
Sterilizing food
What can decay rapidly, do not harm the body, and can be used as tracers in medical diagnoses and studies?
Short-lived isotopes
What is a molecule?
A molecules is a group of atoms held together by energy in the form of a chemical bond
What are the 3 principal types of chemical bonds?
Ionic
Covalent
Hydrogen
What are Van der Waals forces?
They are a kind of weak chemical attractions (not a bond) that come into play when atoms are very close to each other
Are Van der Waals forces
a) directional
b) nondirectional
b) nondirectional
What are ionic bonds?
Ionic bonds involve the attraction of opposite electrical charges
Molecules comprised of ionic bonds are often most stable as?
Crystals
What are covalent bonds?
Directional, strong bonds that form between two atoms when they share electrons
The number of electrons shared varies depending on what?
The number of electrons shared varies depending on how many electrons the atom needs to fill its outermost electron shell
What occurs when atoms attract the shared electrons of a covalent bond (electronegativity)?
This creates tiny partial negative and positive charges within the molecule, now called a polar molecule
What are polar covalent bonds?
These bonds form when the shared electrons of a covalent bond spend more time in the vicinity of a particular atom
What are nonpolar covalent bonds?
These bonds form when there is an equally sharing of electrons between two atoms
What are hydrogen bonds?
They are weak electrical attractions between the positive end of one polar molecule and the negative end of another
What does each atom with a partial charge act like?
They act like a magnet to bond weakly to another polar atom with an opposite charge
Water is what kind of molecule?
a) polar and can form bonds with each other
b) non-polar and can form bonds with each other
a) polar and can form bonds with each other
What can water form?
Water can form hydrogen bonds
What are the 5 properties of water?
Heat property
Ice formation
High heat of vaporization
Cohesion
High polarity
What is Heat Storage?
Water heats up more slowly than other compounds and holds its temperature longer
Why must water require high amounts of energy to vaporize?
Because hydrogen bonds must be broken
What occurs when water vaporizes?
It takes the heat energy with it, allowing for evaporative cooling
What is Ice Formation?
Water molecules move around each other with hydrogen bonds breaking and forming, but, as temperatures drop, the movement of water molecules decreases, allowing hydrogen bonds to stabilize, holding individual molecules further apart
What is High Heat of Vaporization?
If the temperature if high enough, many hydrogen bonds break in water, with the result that liquid is changed into vapor
What is Cohesion?
The molecular attraction between the surfaces of like bodies in contact, such as that between water molecules and other water molecules
“Because water molecules are very polar, they are attracted to other polar molecules - hydrogen bonds bind polar molecules to each other. When the other polar molecule is another water molecule, this attraction is called cohesion”
What is High Polarity?
Water molecules in solution always tend to form the maximum number of hydrogen bonds possible
Polar molecules form hydrogen bonds and are attracted to water molecules
What is adhesion?
When polar molecules other than water stick to a water molecule
What is an example of high heat of vaporization?
Sweating cools the human body off because, as the sweat evaporates, it takes energy with it, in the form of heat, cooling the body
What does Hydrophilic mean?
Describes polar molecules, which form hydrogen bonds with water and therefore are soluble in water
Water Loving
What does Soluble mean?
Refers to polar molecules that dissolve in water and are surrounded by a hydration shell
What is a hydration shell?
A shell of water molecules that prevents the ions from reallocating with the object
What does Hydrophobic mean?
Describes non-polar molecules, which do not form hydrogen bonds with water and therefore are not soluble in water
Water Hating
What is produced when a covalent bond within a water molecule spontaneously breaks?
This produces a positively charged hydrogen ion (H+) and a negatively charged hydroxide ion (OH-)
How can the amount of ionized hydrogen from water in a solution be measured?
Measured as pH
What is the pH scale?
A logarithmic, which means that a pH scale different of 1 unit actually represents a 10-fold change in hydrogen ion concentration
What is the pH of pure water?
7
What is an acid?
