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54 Cards in this Set

  • Front
  • Back
Matter
Anything that occupies space and has mass
What are the three physical states matter on Earth is found in?
1. Solid
2. Liquid
3. Gas
Elements
Substances that cannot be broken down into other substances
What is matter composed of?
Chemical elements
How many naturally occurring elements are there on Earth?
92 (plus several dozen made by humans)
How many naturally elements are essential to life?
25
In order to most to least bountiful, what are the four naturally occurring elements that make up 96% of the human body?
1. Oxygen 65%
2. Carbon 18.5%
3. Hydrogen 9.5%
4. Nitrogen 3.3%
Trace elements
Elements essential for life, but only in very small amounts
Compounds
Substances that contain two or more elements in a fixed ratio. Most of the compounds in living organisms contain several different elements

i.e. NaCl, DNA
Ataom
The smallest unit of matter that still retains the properties of an element. Composed of 3 subatomic particles
What are the three subatomic particles that make up an atom?
1. Proton
2. Electron
3. Neutron
Proton
A subatomic particle with a single unit of positive electrical charge that stays tightly packed into the nucleus
Neutron
An electrically neutral particle that stays packed into the nucleus
Electron
A subatomic particle with a single unit of negative electrical charge. Move around the the nucleus in a spherical cloud
What keeps electrons moving around the nucleus?
The attraction between the negatively charged electrons and the positively charged protons
What does it mean if an atom is "neutral"?
When the atom has an equal number of protons and electrons and the net electrical charge is zero
Atomic number
Determined by the number of protons in an atom (this also determines which element it is)
Mass number
The sum of the number of protons and neutrons in an atoms nucleus
Why are electrons not considered in the atoms atomic and mass numbers?
Electrons has a tiny mass compared to the mass of protons and neutrons which are nearly identical
Isotopes
The different isotopes of an element have the same number of protons and electrons but different numbers of neutrons and therefore differ in mass
Radioactive/unstable isotope
One in which the nucleus decays, giving off particles and energy
Which subatomic particles primarily determine how an atom behaves when it encounters other atoms?
Electrons
What determines how much energy an electron has?
How far away it is from the nucleus (the farther away the greater the energy)
What determines how many electron shells an atom has? How many electrons can each electron hold?
The number of electrons the atom has. The innermost sell holds 2 electrons while the second and third shells each hold 8 electrons
The fullness of which electron shell determines the chemical properties of an atom?
The outermost shells- atom's whose outer shells are full tend not to participate in chemical reactions with other atoms
Chemical bonds

What are the three types of chemical bonds?
An attraction between atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges of the atoms. the bonded atoms gain complete outer electron shells

1. Ionic
2. Covalent
3. Hydrogen
Ions
Atoms tat are electrically charged as a result of gaining or losing electrons
Ionic bonds
The attraction between oppositely charged ions (transfer)

i.e. table salt (Na+ and Cl-)
Covalent bonds
Forms when two atoms share one or more pairs of outer-shell electrons (share)

i.e. O2
Molecule
Atoms held together by covalent bonds
What determines the number of covalent bonds can form?
The number of covalent bonds an atom can form is equal to the number of additional electrons needed to fill its outer shell
Double covalent bond
When two molecules share two pairs of electrons
Polar molecule
Has opposite charges on opposite ends

i.e. oxygen end has a slight negative charge while the region around the two hydrogen atoms is slightly positive
Hydrogen bonds
The weak electrical attractions between hydrogen atoms on one molecule (-) and an oxygen atom on the other molecule (+)
Chemical reaction
Changes in the chemical composition of matter, usually involves the breaking and forming of chemical bonds

*Cannot create or destroy matter, but only rearrange it
Reactants
The starting materials in a chemical reaction
Products
The ending materials in a chemical reaction
What are the four life-supporting properties water possesses?
1. Its cohesive nature
2. Its ability to moderate temperature
3. The significance of ice floating
4. Its versatility as a solvent
Cohesion
The tendency of molecules of the same kind to stick together
The cohesion of water
The cohesion of water is much stronger for water than other liquids. Related to water's high surface tension (how difficult it is to stretch or break the surface of a liquid)
How water moderates temperature
Because of hydrogen bonding, water has a stronger resistance to temperate change than most other substances. It can release a relatively large of amount to the surrounds while its temperature drops only slightly.
This moderates temperatures on earth
What is the difference between temperature and heat?
Heat is the amount of energy associated with the movement of atoms and molecules in a body of matter
Temperature measures the average speed of molecules

Heat is needed to break hydrogen bonds and therefore increase their speed and therefore temperature
Evaporative cooling
When a substance evaporates the surface of the liquid remaining behind cools down (the molecules with the greatest energy tend to evaporate first)
The biological significance of ice floating
Ice floats because it is less dense than the liquid water around it, a consequence of hydrogen bonding
This floating ice insulates the liquid water below it, allowing life under it to persist
Solution
A liquid consisting of a homogenous mixture of two or more substances
Solvent
The dissolving agent, the medium for chemical reactions
Solute
The substance that is dissolved
Aqueous solution
A solution in which water is the solvent
Water as the solvent of life
Water can dissolve an enormous variety of solutes necessary for life as they are polar
Acid
A chemical compound that releases H+ into a solution
Base
A compound that accepts H+ and removes it from the solution
pH scale
A measure of the H+ concentration in a solution on a scale of 0 (most acidic) to 14 (most basic)
Where is pure water on the pH scale?
At 7 as it is neutral and has an equal concentration of H+ and OH-
Buffers
Substances that prevent harmful changes in pH by accepting H+ when it is in excess and donating H+ when it is depleted