Physical Science Test 3
What is the charge of iron (Fe) in the compound Fe2O3?
+3
A metal can best be described as which of the following?
A network solid consisting of positively charged atoms in a sea of electrons
nuclear fission
A nuclear reaction in which a massive nucleus splits into smaller nuclei
Which of the following processes is closest to an ideal reversible process?
A pendulum swinging with almost no friction.
room temperature characteristics of ionic substances?
Brittle, non-conducting solid with high melting points.
Can sulfur be considered a compound and why?
No, it is composed of only one type of atom
Why is fusion generally considered a preferable potential energy source?
Primarily because of the difference in the waste products
When you compare saturated with unsaturated fatty acids containing the same number of carbon atoms, what is true?
Saturated fatty acids have more hydrogen atoms.
covalent bonding
a bond formed when atoms share one or more pairs of electrons. nonmetals + nonmetals. make molecules
Intamolecular forces
a force btween atoms within a single molecule. These forces are stronger than intermolecular forces. covalent bonds!
sea of electrons
a model for how the valence electrons of metal atoms are mobile and can drift from one part of a metal to another (allows for good conductivity)
a proton has a mass that is _____________ of the mass of a neutron
about the same
band gap
an energy gap that exists between the valence band and conduction band of semiconductors and insulators
H20 is a
polar molecule
an element is a substance made up of atoms that all have the same number of...
protons
beta decay
radioactive decay in which an electron is emitted, changes the element! becomes a smaller and more stable nucleus
Two types of processes
reversible and irreversible
metallic bonds conduct...
the best!
releases the most energy on a graph
the biggest decrease
Reversible process
capable of returning to initial state. ex, water or pendulum without friction
Current can flow in all directions in an LED.
false
Metals have higher ionization energies than non-metals do.
false!
intermolecular forces
forces between molecules
dipole-dipole forces
forces of attraction between polar molecules, positive attracted to negative and vice versa
set of properties is most likely those associated with methane, a covalently bonded compound?
gas at room temperature, colorless, does not conduct electricity when solid
Which of the following is NOT why alloys are useful to us today?
have a higher conductivity rate.
why use copper for wiring?
high conductor, high melting point, and malleable
ionic bonding
metals+nonmetals, move around less
Alloys
mixtures of two or more metals, bronze=copper+tin, stronger than alone metals
What classification of matter is magnesium chloride?
network matter
Which type of atom has the highest ionization energy?
nonmetals
Irreversible process
not able to be restored to initial state, the total disorder of the universe increases
alpha decay
2 protons and 2 neutrons (a helium nucleus) that is emitted during radioactive decay. changes the element!
How do semiconductors change with increasing temperatures?
When you heat them up, semiconductors act more like metals.
metals can bend and stretch because...
of the sea of electrons
metallic bond properties
1. Malleability 2. High melting point 3. opaque 4. Shiny 5. Good conductors
ionic bond properties
1. high melting point 2. non-conductive 3. brittle 4. transparent
nuclear fusion pros
1. lots of fuel 2. releases a LOT of energy 3. no radioactive material- helium is easy to find 4. the sun does this!
nuclear fission pros
1. low activation energy 2. efficient, get a lot more than we put in 3. easy chain reactions 4. what we do in a power plant
covalent bond properties
1. low melting point 2. nonconductive 3. transparent
nuclear fission cons
1. not very abundant fuel 2. radioactive material, causes cancer
nuclear fusion cons
1. requires a LOT of energy 2. not efficient, we get less than we put in
What happens to the entropy of the universe as the products are formed in an exothermic chemical reaction?
Chemical potential energy is converted into thermal energy resulting in an increase in entropy.
In order for a chemical reaction to occur
Entropy must increase as a result of the reaction
When you compare the band gap for a red and a blue LED, what is true?
The red LED has the smallest band gap.
A refrigerator is normally run with its door closed. What would happen if the refrigerator were placed in the middle of a closed room with its door open and turned on?
The room would heat up because all of the energy absorbed by the refrigerator, both thermal and electrical potential, is released back into the room as thermal energy.
What best describes how oxygen molecules would behave if mixed with water?
They would dissolve poorly or not at all because they are not polar.
Fish that swim in the cold north Atlantic would have what type of fatty acid in their blood?
Unsaturated acids with lots of double bonds.
hydrogen bonding forces
attraction of hydrogen to O, F, and N. the MOST strong
Although fusion is preferred, why are all commercial nuclear power plants using energy from fission?
because controlled fission generates large amounts of energy while current methods for controlling fusion use more energy than they produce.
Why are metals opaque?
because metals have empty, overlapping orbitals for their electrons
In which kind of radioactive decay would the number of protons in the resulting nucleus be more than in the initial nucleus?
beta decay
polar molecules need
both a positive and negative side
Which of the following is NOT a characteristic of a metal or alloy?
brittle
molecules are always...
covalent!
The force that holds molecules that do not have positive and negative sides to one another
dispersion force
3 types of forces
dispersion, dipole, hydrogen
polar molecules dissolve ________ in water
easily
semiconductors
elements that conduct an electric current under certain conditions. not quite metals or non metals, have similar properties to metals
In an irreversible process, the overall disorder of the universe...
increases
what is holding one water molecule to another water molecule?
intermolecular force
highest activation energy on a graph
is the highest energy peak
Two atoms that have the same atomic numbers but different atomic mass numbers are called
isotopes
half-life
length of time required for half of the radioactive atoms in a sample to decay
How does a catalyst affect a reaction?
lowers activation energy
How does the mass of a proton compare to the mass of an electron?
mass of the proton is much larger than the mass of an electron
metallic bonds
the force of attraction that holds metals together; it consists of the attraction of free-floating valence electrons for positively charged metal ions
When you compare the mass of the products to the mass of the reactants in a fission reaction, what do you find?
the reactants have more mass
gamma decay
the release of gamma rays from a nucleus, nothing changes. happens when there is excess energy inside of the atom
dispersion forces
the weakest of all molecular interactions, are caused by the motion of electrons, only for non polar molecules
Chemical reactions always increase the total entropy of the universe
true
