U1 Chapter 2: The Chemical Context of Life Flashcards
Matter
Anything that takes up space and has mass
Element
A substance that cannot be broken down to other substances by chemical reactions
Compound
A substance consisting of two or more different elements combined in a fixed ratio
Essential Elements
An organism needs to live a healthy life and reproduce
Trace Elements
Required by an organism in only minute quantities, some trace elements such as iron (Fe) are needed by all forms of life; others are required only by certain species
Atom
The smallest unit of matter that still retains the properties of an element
Half-Life
The time it takes for 50% of the parent isotope to decay
Radiometric Dating
Scientists measure the ratio of different isotopes and calculate how many half-lives (in years) have passed since an organism was fossilized or a rock was formed
Energy
The capacity to cause change, ex. by doing work
- potential energy, is the energy that matter possesses because of its location or structure
Covalent Bond
The sharing of a pair of valence electrons by two atoms
Single Bond
A pair of shared electrons
Electronegativity
The attraction of a particular atom for the electrons of a covalent bond
Nonpolar Covalent Bond
The electrons are shared equally because the two atoms have the same electronegativity–the tug of war is at a standoff
- polar covalent bonds are where the electrons are not equally shared
Cation
A positively charged ion
Anion
Negatively charged ion
Ionic Bond
Cation and Anion attraction
Hydrogen Bond
Noncovalent attraction between a hydrogen and an electronegative atom
Van Der Waals Interactions
Individually weak and occur only when atoms and molecules are very close together and when such interactions occur simultaneously, it can be powerful like a gecko climbing a wall
Chemical Equilibrium
The point at which the reactions offset one another
- this is a dynamic equilibrium where reactions are still going on in both directions, but with no net effect on the concentrations of reactants and products
