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What is an element?
is a substance that cannot be broken down to other substances by ordinary chemical means.
How many elements are there in nature?
there are 92 natural elements on earth
How many are essential to life?
25 of the 92 natural elements are essential to life
Which 4 make up 96% of all elements found in cells?
What is a trace element?
an element that is essential for life but required in extremely minute amounts
is a substance consisting of two or more different elements combined in a fixed ratio.
How do compounds demonstrate the emergent property theme?
element to compound
-ex: NaCl (sodium choloride)=table salt
smallest unit of matter that retains properties of an element
Differentiate between protons, neutrons, and electrons (size, location, charge). Differentiate between atomic number and mass number.
Describe an isotope and be able to recognize one.
have the same number of protons and electons but different number of neutrons
-pg. 20, table 2.3
Describe “electron shell”.
an energy level representing the distance of an elctron from the nucleus of an atom.
an atom may have 1, 2, or 3 electron shells
Know the maximum number of electrons that can be in the first 3 electron shells.
the 1st electron shell has only one orbital and can hold only 2 electrons.
the second and third rows, the outer shell has four orbitals and can hold up to 8 electrons (4 pairs)
Define ion, molecule, reactant, and product.
ion: is an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons
molecule: two or more atoms held together by covalent bonds
reactant: conversion of the starting materials
product: the material resulting from the chemical reaction
Differentiate between ionic, covalent, and hydrogen bonds.
ionic bond: 2 ions with opposite charges that attract eachother and the ions are held togeher (opposites attract)
covalent bond: the strongest kind of chemical bond in which two atoms share one or more paris of outer-shell electrons.
hydrogen bond: a type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule
Know the difference between nonpolar and polar covalent bonds
nopolar covalen bond: equal pull between atoms
polar covalent bond: unequal pull between atoms of different elements/electonegativities-polar molecules
List and describe the 4 properties of water that help support life.
1: cohesion, adhesion, surface tension
2: resists temperature change
3: water can exist as a gas, liquid, and solid. it is less dense as a solid due to hydrogen bonding
4: solvent of life: solvent (the dissolving agent) and solute (the substance dissolved)
the sticking together of molecules of the same kind, often by hydrogen bonds.
attraction between different kinds of molecules
Define surface tension
a measure of how difficult it is to break the surface of a liquid-hydrogen bonds are responsible for surface tension (ex: bg able to float in water)
energy associated with movement of atoms and molecules in matter
measures the intensity of heat
liquid consisting of a uniform mixture of two or more substances
the dissolving agent of a solution
a substanc that is dissolved in a solution
Define acid, base, and buffer.
acid: substance that increases the hydrogen ion concentration in a solution (H+) hydrogen ions
Base: substance that increase the hydrogen ion concentration in a solution (OH-) hydroxide ions
buffer: a chemical substanc that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
Recognize the difference between a hydrogen ion and a hydroxide ion.
hydrogen ions are acids
hydroxide ions are base
Know how to read the pH scale (where the acids are, where the bases are, where neutral is, and how much change each pH unit represents).
acids from 0 to 6
7 is neutral
base from 8 to 14
*concentration is 10x greater each step
In what pH range are most biological fluids?
they are between 7 to 7.8