Unit 2-Chemistry Flashcards
Define matter
Anything that occupies space and has mass. Found on earth in three physical states : solid liquid and gas
Define elements
A substance that cannot be broken down to other substances by ordinary chemical means
What are the four common elements
Oxygen
Carbon
Hydrogen
Nitrogen
Define a molecule
Formed when two or more atoms are joined chemically
Define a compound
A substance consisting of two or more different elements combined in a fixed ratio
More common then pure elements
Define an atom
The smallest unit of matter that still retains the properties of an element
Define a proton
A subatomic particle with a single positive electrical charge
Define an electron
A subatomic particle with a single negative charge
Define a neutron
Has no charge
Define atomic number
Number of protons in a molecule
Note it’s also the number of electrons
Define mass number
And atomic mass
The sum of the number of protons and neutrons in its nucleus
Protons and neutrons pretty much weigh the same
Atomic mass is approximately equal to its mass number
What are two types of ions
Cations (+)
Anions (-)
Define isotopes
When an element has the same number of protons and behave identically in chemical reactions but they have different numbers of neutrons
Example of isotopes
Carbon isotopes Carbon 12 (6 neutrons) Carbon 13 (7 neutrons) Carbon 14 (8 neutrons) But they all have the same number of protons (6)
Stable isotopes
Their nuclei remain intact more or less forever
Ex) C12 an C13
Radioactive isotopes
When the nucleus decays spontaneously giving off particles and energy
Can cause damage
Ex) C14
Define electron shells and valence shells
Electron shells= what electrons orbit on
Valence shell= the number of electrons in the outermost shell
What do valence shells determine
The chemical properties of an atom
Atoms whose outer shells are not full tend to interact with other atoms
How do chemical interactions between atoms enable them to fill their outer electron shells
When two atoms with incomplete outer shells react each atom will share donate or receive electrons so that both partners end up with completed outer shells
Chemical bonds
An attraction that holds atoms close together
What is the strongest kind of chemical bond
Covalent bond
Define covalent bonds
Two atoms share one or more pairs of outer shell electrons
This forms a molecule
What is a single covalent bond
The sharing of a pair of electrons
1 electron from each atom
How many covalent bonds can an atom form?
It depends on the number of additional electrons needed to fill its outer(valence) shell
Ie a double bond
Define electronegativity
An atoms attraction for shared electrons
The more electronegative an atom the more strongly it pulls shared electrons toward its nucleus
Define non polar covalent bonds and give examples
Electrons are shared equally between the atoms
Ex) O2 and H2 the two identical atoms exert an equal pull
Methane is non polar because carbon and hydrogen are not much different in electronegativity
What is one of the most electronegative elements
What does this make this atom
Oxygen
(Also nitrogen)
Oxygen attracts the shared electrons more strongly
A polar covalent bond
Define a polar covalent bond
Give an example
The pulling of shared negatively charged electrons closer to the more electronegative atom makes that atom partially negative and the other atom partially positive
H2O
Define a polar molecule
Give an example
Has an unequal distribution of charges
Negative at water end
Positive at hydrogen end
Define an ion
An atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons
Define an ionic bond
Give an example
When an attraction holds two ions with opposite charges together to fill the outer electron shell
Electron donations
Crystal
Define hydrogen bond
What type of strength are these
When the positively charged region in this type of bond is always hydrogen then we call it a hydrogen bond
A hydrogen atom that has formed a polar covalent bond with an electronegative atom had a partial positive charge
Weak bonds
What enables neighbouring water molecules to hydrogen bond to one another
The molecules are polar with the negative end (oxygen) of one molecule attracted to a positive end (hydrogen) of its neighbour
Define chemical reaction
The breaking and making of chemical bonds leading to changes in the composition of matter
Do not create or destroy matter
Define reactants
Beginning materials of a chemical reaction
Define products
The material resulting from the chemical reaction
Define cohesion
When molecules of the same kind stick together and is much stronger for water.
Hydrogen bonds between water
Define adhesion
The clinging of one substance to another
Define heat
The amount of energy associated with the movement of atoms and molecules in a body of matter
Define temperature
Measures the intensity of heat. The average speed of molecules rather then the total amount of heat energy in a body of matter
Define evaporation
Occurs because the molecules with the greater energy leave
Define a solution
A liquid consisting of a uniform mixture of two or more substances
Define a solvent
The dissolving agent
Define a solute
A substance that is dissolved
Define an aqueous solution
When water is the solvent
What are the two ions formed from dissociation of water
Hydroxide ions (OH-) Hydrogen ions (H+) They are both very reactive
Define acids
More H+ ions
A compound that donates hydrogen ions
Define a base
A compound that accepts hydrogen ions and removes them
Donates OH- and that combined with the H+ to form H2O
Less H+ ions
More OH-
Define a pH scale
A scale used to describe how acidic or basic a solution is Ranges from 0-14 0-6= acid 7= neutral 8-14= basic Each notch is x10 H+
Changing the ___ would change it into an atom of a different element
Number of protons in the nucleus of an atom
Your body contains the smallest amount of which element
Phosphorus
A solution at pH 6 contains ___ then the same amount of a solution at pH 8
100 X more H+
Most of the unique properties of water result from the fact that water molecules __
Are polar and form hydrogen bonds
A sulphur atom has 6 electrons in its outer shell. As a result it forms __ covalent bonds with other atoms
Two
What does the word trace mean when you’re talking about a trace element
The element is required in very small amounts
A can of cola consists mostly of sugar dissolved in water with some carbon dioxide gas that makes it fuzzy and makes the pH less the 7. In chemical terms you could say the cola is an aqueous solution where water is the __ sugar is a __ and carbon dioxide makes the solution __
Solvent
Solute
Acidic
Radioisotopes can be used in medical studies because __
Their location or quantity can be determined because of their radioactivity
True or false
Table salt, water, and carbon are compounds
False
True or false
The smallest unit of an element is a molecule
False
True or false
A bathtub full of lukewarm water may hold more heat then a teakettle full of boiling water
True
True or false
If the atoms in a molecule share electrons equally the molecule is said to be non polar
True
True or false
Ice floats because water molecules in ice are more tightly packed then in liquid water
False
True or false
Atoms in a water molecule are held together by the sharing of electrons
True
True or false
Most acid precipitation results from the presence of pollutants from aerosol cans and air conditioners
False
True or false
An atom that has gained or lost electrons is called an ion
True
Define organic compounds
Carbon based molecules
What is one of the simplest organic molecules
Methane
Define hydrocarbons
What are two examples
Compounds composed of only carbon and hydrogen
Methane and propane
Define carbon skeleton
The chain of carbon atoms in an organic molecule
Define isomers
Compounds with the same formula but different structural arrangements
