Chapter 2 Flashcards
Matter
anything that takes up space and has mass
Solid –> Liquid –> Gas–>Plasma
Element
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 Element
Elements needed by an organism for optimal health. Humans need 25, Plants only need 17 elements. Just 4 elements (O, C, H, and N) make up 96% of all living matter. The other 4% are mainly Ca, P, K, and S.
Trace Elements
elements that are required by an organism in minute quantities (Fe, Mg, I…)
Atoms
smallest unit of matter that still retains properties of the element
Protons
has +1 charge, found in nucleus
Neutron
has 0 charge, found in nucleus
Electron
has -1 charge, found in electron cloud surrounding nucleus
Atomic number
equal to number of protons, identifies element.
top left number on the periodic table of an element
Mass Number
equal to number of protons + neutrons
Isotopes
different forms of same element (have same # of protons, but different # of neutrons)
Atomic Mass
average mass of all naturally occurring isotopes of an element
Electron shells
region in which electron is likely to be found (average distance)
Valence Electrons
electrons in the outermost electron shell when the e - is in the ground state
Electronegativity
attraction of particular atom for the electrons in a covalent bond
Weak Bonds
Biologically important in large quantities or large molecules
Hydrogen Bond
attraction between a hydrogen (delta+) from one molecule and an electronegative atom (delta-) from another molecule - important for understanding water.
Van der Waals Interactions
Occur from temporary dipoles when atoms are in close contact with other atoms or molecules. Individually weak, but strength in numbers.
Chemical Reactions
conversion of starting materials (reactants) to products (some reversible)
a process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction.
Rate of reaction
increases with higher concentration of reactants, slows as products accumulate
the speed at which a chemical reaction proceeds. It is often expressed in terms of either the concentration (amount per unit volume) of a product that is formed in a unit of time or the concentration of a reactant that is consumed in a unit of time.
Chemical Equilibrium
in a reversible reaction, that dynamic stability in which there is no net change in amount of reactants or products
Properties of water
Water has many unique properties that make it necessary for all living things. Water is the universal solvent - most ionic and polar substances dissolve in water. Cells are 70 - 95% water. Hydrogen bonds (H-bonds) are responsible for most of water’s remarkable properties
Cohesion
water sticks to self (pulls water up plant)
cohesion refers to the sticking together of alike molecules, such as water molecule being attracted to another water molecule. Cohesion also causes water molecules to form drops. Together with adhesion, It helps to explain the occurrence of surface tension and capillarity. … cohesive attraction.
