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What is an element?
is a substance that cannot be broken down to other substances by ordinary chemical means.
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How many elements are there in nature?
there are 92 natural elements on earth
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How many are essential to life?
25 of the 92 natural elements are essential to life
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Which 4 make up 96% of all elements found in cells?
Carbon (C)
Oxygen (O)
Nitrogen (N)
Hydrogen (H)
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What is a trace element?
an element that is essential for life but required in extremely minute amounts
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Define compound.
is a substance consisting of two or more different elements combined in a fixed ratio.
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How do compounds demonstrate the emergent property theme?
element to compound
-ex: NaCl (sodium choloride)=table salt
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Define atom.
smallest unit of matter that retains properties of an element
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Differentiate between protons, neutrons, and electrons (size, location, charge). Differentiate between atomic number and mass number.
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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
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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
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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)
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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
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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
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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
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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)
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Define cohesion
the sticking together of molecules of the same kind, often by hydrogen bonds.
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Define adhesion
attraction between different kinds of molecules
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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)
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Define heat
energy associated with movement of atoms and molecules in matter
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Define temperature
measures the intensity of heat
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Define solution
liquid consisting of a uniform mixture of two or more substances
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Define solvent
the dissolving agent of a solution
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Define solute
a substanc that is dissolved in a solution
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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.
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Recognize the difference between a hydrogen ion and a hydroxide ion.
hydrogen ions are acids
hydroxide ions are base
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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
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In what pH range are most biological fluids?
they are between 7 to 7.8
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