Transcript Summative Assessment Review!

Summative Assessment Review!
Ms. Barlow’s HS PS Class
Particle Properties
Phase
Proximity
Energy
Motion
Volume
Shape
Solid
close
little
vibrational
definite
definite
Liquid
close
moderate
rotational
definite
indefinite
far apart
a lot
translational
indefinite
indefinite
Gas
Phase Change Diagram
Gas Laws
• Boyle determined that for the same amount
of a gas at constant temperature, results in an
inverse relationship: when one goes up, the
other comes down.
Charles’ Law
• As the volume increases the temperature also
increases. If the temperature decreases than
the volume also decreases.
• ATOMIC NUMBER: the number of
protons in the nucleus of an atom.
Atomic Mass – Atomic Number = Number of Neutrons
Number of Protons = Number of Electrons
•Valence Electrons
• Farthest away from the nucleus and are
involved in bonding
• Electron Dot Diagram: Way to show the #
of valence electrons.
Gain or loss of electrons is called ionization
lose an electron; atom becomes positive
gain an electron; atom becomes negative
•Isotopes
• Atoms with the same number of protons but a
different number of neutrons.
• Example: an atom with one proton, one
electron and one neutron is hydrogen.
• However, if the hydrogen atoms has two
particles (neutrons) but the same number of
protons (in the case of hydrogen one) it is an
isotope of hydrogen.
Radioactivity
• Radioactivity is the breaking down of
atomic nuclei by releasing particles
(primarily alpha and beta particles)
or electromagnetic radiation
(primarily gamma rays).
Alpha Particles
• Alpha particles are positively charges particles.
• Alpha particles consists of two protons and
two neutrons.
• An alpha particle is simply a helium nuclei (He)
which is ejected with high energy from an
unstable nucleus
• When an atom loses an alpha particle, the Z
number (atomic number) is lower by two, so
move back two spaces on the periodic table to
find what the new element is. The new
element has an A number (atomic mass
number) that is four less than the original
elements.
Example
Beta Particles
• Beta particles are electrons. They are
negatively charged (-1).
• They are fast moving because they are actually
electrons.
• It is produce when a neutron in the nucleus
breaks up into a proton and an electron.
• The proton remains inside the nucleus,
increasing its atomic number by one but the
electron is given off.
•
Example – Carbon -14
• They are written as an electron
(along with a proton) which is emitted from the
nucleus as a neutron decays.
• The Z number (atomic number) actually adds
one since its total must be the same on both
the left and the right of the arrow and the
electron on the right adds a negative one.
• The A (atomic mass)number is unchanged.
• The Z number determines the element so look
for it on the Periodic Table.
Gamma Rays
• Gamma rays are electromagnetic waves with
extremely short wavelengths.
• They have no mass or charge so the Z and A
numbers are not affected.
• They travel at the speed of light.
• It takes a thick block of lead to stop them.
• Radioactive atoms often emit gamma rays
along with either alpha or beta particles.
Examples
Name
Alpha
Beta
Gamma
Greek
letter

-

2p+, 2n0
electron
EM wave
2+
1-
0
wood, glass
thick
concrete or
lead
Symbol
Composition
Charge
Stopped
by
paper, skin,
clothing
C N  e
14
6
218
84
14
7
0
1
Po He 
214
82
142
61
4
2
______________
Pb
Pm e Nd
0
1
142
60
a. alpha emission
b. beta emission
c. electron capture
_______________
_______________
Standard: Explain the process of halflife as related to radioactive decay.
Radioactive Decay
• During radioactive decay an unstable nucleus
spontaneously decomposes to form a different
nucleus, giving off radiation in the form of
atomic particles or high energy rays.
• This decay occurs at a constant, predictable
rate that is referred to as half-life.
• A stable nucleus will not undergo this kind of
decay and is thus non-radioactive.
Calculating Half-Life
• http://www.wikihow.com/Calculate-Half-Life
• Solve the following problem: If 20 mg of
iodine 31 is given to a patient, how much is
left after 32 days? The half-life of iodine-131 is
8 days. Here's what you do:
Here's what you do:
• Find how many times the substance will be halved in
32 days. Do this by seeing how many times 8, the halflife of the substance, can go into 32, the amount of
days. 32/8 = 4, so the amount of substance is halved
four times.
• This means that after 8 days, you will have 20mg/2, or
10 mg of substance; after 16 days, you will have 10
mg/2 or 4 mg left of the substance; after 24 days, you
will have 5 mg/2, or 2.5 mg left of the substance, and
after 32 days, you will have 2.5 mg/2, or 1.25 mg left of
the substance.
• Solve the following problem: If a laboratory
receives a shipment of 200 g of technetium99m and only 12.5 of the isotope remains,
what is the half-life of technetium-99m?
Here’s what you do:
• Work backwards. If 12.5g of the substance
remains, then before it was halved, there was
25 g of the substance (12.5 x 2); before that,
there was 50 g of the substance; before that,
you had 100g, and before that, you had 200g.
• This means that the substance had to be
halved 4 times to get from 200 g to 12.5 g,
which means that the half life is 24 hours/4
times, or 6 hours.
• Solve the following problem: If the half-life of
uranium-232 is 70 years, how many half-lives
will it take for 20g of it to be reduced to
1.25g?
Here’s what you do:
• Start with 20g and start reducing. 20g/2 = 10g
(1 half life), 10g/2 = 5 (2 half lives), 5g/2 = 2.5
(3 half lives), and 2.5/2 = 1.25 (4 half lives).
The answer is 4 half lives.
Nuclear Fission
• The splitting of a nucleus into smaller
fragments is called nuclear fission.
• Heavy atoms (mass number>60) tend to break
into smaller atoms, thereby increasing their
stability.
• Nuclear fission releases a large amount of
energy.
Nuclear Fission
• A chain reaction can only occur if the starting
material has enough mass to sustain a chain
reaction. This amount is called the critical mass.
• Nuclear Fission is what occurs in Nuclear Reactors
and Atomic Bombs.
• The Nuclear reactor is a controlled fission reaction,
the bomb is not.
Nuclear Fusion
• The combining of atomic nuclei to form a
larger atom is called fusion
• Nuclear fusion occurs in the sun where
hydrogen atoms fuse to form helium
1
1
4 H + 2
0 e-1
 He + energy
4
2
Nuclear Fusion
Fusion
• Fusion reactions also release very large
amount of energy but require extremely high
temperatures to start.
• Nuclear fusion also occurs in new stars and is
how all of our elements were made.
4
2
4
He + He

2
4
2
Be 
He +
8
4
Be84 + energy
12
6
C + energy
Decay vs. Nuclear Reactions
• Alpha, beta, and gamma
• Nuclear reactions involve
decay occur as ONE atom
more than just getting rid of a
tries to increase it’s
few protons or neutrons. The
stability by getting rid of a
new atoms produced are VERY
few neutrons, or protons &
different elements than the
neutrons.
reactant.
• The product is an alpha,
• Nuclear reactions must be
beta, or gamma particle
started, so there are 2 things
and ONE new atom. There
on the left hand side.
is only ONE thing on the
– Nuclear fission: makes 2 or
left hand side.
more much smaller atoms
– Nuclear fusion: makes 1
much larger atom