Chapter 2: Water and Carbon: The Chemical Basis of Life Flashcards
Atom
Smallest identifiable unit of mass
When the number of protons and electrons in an atom are the same
The charges balance and make the atom neutral
Elements
Fundamental substances that cannot be broken down
atomic number
number of protons in the nucleus of an atom
Mass number
The sum of the protons and neutrons in an atom
Isotopes
Forms of an element with different number of neutrons
atomic weight
average of all the masses of the naturally occuring isotopes based on their abundance in nature.
Radioactive isotope
Nucleus will decay and release energy in the form of radiation.
Orbitals
Electrons move around in this regions and each orbital can hold 2 electrons.
Electron shells
Orbitals are grouped into levels electron shells. Electrons in outershells have more energy than those in the inner shell.
Valence shell
Outermost electron shell of an atom
Valence electrons
An electron in the outermost electron shell. Involved in chemical bonding
Valence
Number of unpaired electrons found in an atom’s valence shell
Chemical bonds
Attractive force binding two atoms together, types being covalent, ionic and hydrogen bonds.
Covalent bond
When two atoms share electrons
Compounds
Atoms of different elements are bonded together.
Electronegativity
A measure of how strongly an atom pulls shared electrons toward itself in a bond.
The number of protons in the nucleus and the distance between the nucleus and valence shell determine the electronegativity.
Basically when you move vertically down on the periodic table elements with more shells have less electronegativity and if you move horizontally to the right, you’ll see higher electronegativities due to more protons.
Oxygen
eight protons and only 6 valence electrons, making it the most electronegative of all elements. Thus it attracts covalently bonded electrons strongly.
nonpolar covalent bond
A bond that involves equally shared electrons is called
H-H and CH4 are examples because they share electrons equally.
Polar covalent bond
Covalent bonds in which electrons are shared unequally between atoms that differ in electronegativity. It results in the more electronegative atom having a partial negative charge and the other atom having a partial positive charge.
Ionic bonds
Electrons are completely transferred from one atom to the other. It gives the 2 resulting atoms a full valence shell.
Cation
Positively charged ion
Anion
Negatively charged ion
Molecular formulas
Indicates only numbers and types of atoms in a molecule
Structural formulas
Notation where the chemical symbols for the constitute atoms are joined by straight lines representing single, double or triple bonds
ball and stick models
representation of a molecule where atoms are shown as ball colored
Space fillng models
Depict relative sizes of atoms and spaital relationships
aqueous
water based environment
solvent
agent for dissolving or getting substances into solution.
solution
liquid containing one or more dissolved solids or gases in a homogenous mixture
solutes
Any substance that is dissolved in a liquid
Polar
Asymmetrical or undirectional, carries positive charge on one side of a molecule and a partial negative charge on the other.
hydrogen bond
a weak attraction between a hydrogen atom with a partial positive charge and another atom usually oxygen or nitrogen, with negative charge.
hydrophilic
Interacts readily with water, these are typically polar compounds containing partially or fully charged atoms
hydrophobic
Doesn’t interact readily with water, typically are nonpolar molecules
Hydrophobic interactions
Weak interactions between nonpolar molecules when exposed to an aqueous solvent.
van der Waals interactions
weak electrical attraction between two nonpolar molecules on parts of a molecule that had been brought together by hydrophobic interactions
London dispersion force
If nonpolar molecules get extremely close to each other, the partial charge on one molecule induces an opposite charge in a nearby one and it causes an attraction. This attraction is weaker than covalent and hydrogen bonds.
Cohesion
Tendency of certain molecules to cling together due to attractive forces
Adhesion
attraction between unlike molecules is called adhesion
Surface tension
The cohesive force caused by attraction between the molecules at the surface of a liquid. Water has a high surface tension because hydrogen bonds among water molecules resist stretching or breaking the surface. Water molecules are more strongly cohesive to each other than they are to air.
specific heat
amount of energy required to raise the temp of 1 gram of a substance by 1 C
heat of vaporization
the energy required to change 1 gram of water from liquid to gas
chemical reaction
one substance is combined with others or broken down into another substance
reactant
starting materials in a chemical reaction, shown on the left
product
Final materials formed in a chemical reaction, molecules shown to the right.
hydrogen ion (H+)
single proton with positive electric charge of +1
hydroxide ion (OH-)
An oxygen atom and a hydrogen atom joined by a single covalent bond and carrying a negative electric charge of -1
Chemical equilibrium
A dynamic but stable state of a reversible chemical reaction in which the forward reaction and reverse reactions proceed at the same rate. The concentrations of reactants and products stay the same.
Acids
Substances that give up protons during chemical reactions and raise the hydronium ion concentration of water
Bases
Molecules or ions that acquire prtons during chemical reactions and lower the hydronium ion concentration of water are called bases.
Mole
amount of substance that contains 6.022 x 10^23 of its elemental entities
Molecular weight
the sum of the atomic weights of all the atoms in a molecule, the total number of protons and neutrons in the molecule
Molarity
number of moles of the solute present per liter of solution.
PH
Measure of concentration of protons in a soultion and thus how acidic or basic the solution.
pH scale
Pure water is used as a standard or point of reference for pH 7 on the pH scale. Anything below pH 7 gets more acidic and anything that goes above pH 7 is basic
Whem ph is less than 7
The concentration is acidic and the concentration of hydrogen ions is greater than the concentration of hydroxide ions
The higher the ph
The less acidic the solution and lower the
buffers
Compounds that minimise changes in pH are called buffers
system
substances you want to focus attention on.
Open system
Can exchange energy with environment
Can exchange matter with environment
Closed system
Cannot exchange energy with environment
Isolated system
Cannot exchange energy with environment
Cannot exchange matter with environment
endothermic
Referring to chemical reaction that absorbs heat
exothermic
chemical reaction that releases thermal energy to the environment
Energy
Capacity to do work or supply heat.
Potential energy
Stored energy.
Chemical energy
Molecule’s potential to form stronger bonds is a type of potential energy called chemical energy
Kinetic energy
Energy of motion
Thermal energy
Kinetic energy of molecular motion
Temperature
measures how much thermal energy its molecules possess. A object’s molecules are faster if the temperature was raised to make it hot.
Heat
Thermal energy transferred between objects of different temperatures
First law of thermodynamics
Energy is conserved-it cannot be created or destroyed but only transferred and transformed
Spontaneous reactions
a reaction that occurs in a given set of conditions without interventions
Entropy
amount of disorder in a system
increases in a system where the products of a chemical reaction are less ordered than the reactant molecules.
second law of thermodynamics
states that in all spontaneous reactions, entropy always increases when both system and its environment are taken into account
Oxygen compounds
A group of molecules that include at least one carbon atom
Functional groups
Small group of atoms bonded together in a precise configuration.
6 functional groups commonly attached to carbon atoms
amino group: HNH : Acts as a base - tends to attract a proton to form
Carboxyl group: O-C-OH
Carbonyl group: O-C-H
Hydroxyl group: OH
Phosphate: PO4
Sulfhydryl: SH
Amino and carboxyl functional group
tends to attract or relase hydrogen ion (proton)
Amino groups function as bases; carboxyl groups act as acids
Amino group: HNH
Carboxyl group: COOH
Carbonyl groups
Found on molecules such as acetaldehyde and acetone. Site of reactions that link these molecules into larger and more complex organic compounds.
OCH
Hydroxyl groups
Important because they act as weak acids. Protons involved in acid-base reactions come from hydroxyl groups on organic compounds.
Due to them being polar, they will form hydrogen bonds and tend to be soluble in water
OH
Phosphate groups
Carry negative charges on two of their oxygen atoms. When the phosphate groups are transferred from one compound to another the change in charge dramatically affects the structure of the recipient molecule
Sulfhydryl groups
Consists of a sulfur atom bonded to a hydrogen atom
Macromolecules
Large molecules, made up of smaller molecular subunits joined together
Monomer
small molecule that can covalently bind to other similar molecules to form a large macromolecule
polymer
large number of monomers are bonded together
Polymerization
process in which many identical or similar small molecules (monomers) are covalently bonded to form a large molecule (polymer)
Polymerization reaction
organizes multiple simpler monomers into a single more complex and ordered structure. Decreases the disorder, or entropy of the molecules involved
Condensation reaction
Chemical reaction in which two molecules are joined covalently with removal of an -OH from one and an -H from another to form water
Dehydration reactions
Another word for condensation reaction.
Hydrolysis
Breaks molecules apart by adding a water molecule
