Transcript Protons, Neutrons and Molar Mass

WHOT:


Monday 12/8
Objective: calculate specific dates of
radioactive isotopes.
Responsibilities: Lab Due tomorrow.
 Decay
WS Due Tomorrow.
Warm-up


You have 12g of radioactive material. How much
will still be radioactive after 2 half-lives?
How much time has gone by if each half life is 1
hour?


Parent Isotope
(before decay)
Daughter Isotope
(after decay)
Radioactive
particle (any)
Parent Decay  Daughter Formation Curve
120
% of Isotope
100
80
And so on…
Total
Start
# of
21Half-Lives
Half-Life
25
50Atoms
parents;
100
parents;
50daughters
daughters
075
remains
same
60
40
Average Mm Remaining
Average Daughter
20
0
0
1
2
3
4
5
6
7
# Half-lives
8
9
10
11
12
Radiometric Dating

Every radioactive isotope has a unique half-life
If you know the original amount of radioactive material,
it is possible to determine the age of that sample.

Two common isotopes

 Carbon-14
 Has
half life of 5,730 years
 Used to detect up to about 50,000 years old
 Uranium-238
 Half-life
= 4.5 billion years. Can detect the really old.

For C-14 dating, the object must have carbon in it.
 Object
must have died recently enough to still have
carbon-14 in it
 There is always the same amount of C-14 in life.
 When you die, you stop getting this new C-14
 Find
out how much C-14 you have, find out when something
died.

For U-238 dating,
 The
object must have uranium in it… you get the idea
Practice
If a sample contains an isotope with a half-life of 20,000
years, how old would the sample be if:
Hint:
 ½ the original isotope remain?
Always start by
 20,000 years
figuring out how
many half-lives
there were.


1/8 the original isotope remain?
 60,000 years
What percent of the sample would be left if the sample
was 40,000 years old?
 25%
(or ¼)

Worksheet
 If
you finish early there is a game online you can play.
Check the SWIFT blog.
Radioactive dating game

Linked to my web page, or go to:
 https://phet.colorado.edu/en/simulation/radioactive-
dating-game
WHOT Q

Create a question about C-14 dating
 Think…
Either about the conditions needed to do it
 Or
A
practice problem.
WHOT:



Tuesday 12/9
Turn in: Yesterday’s decay WS, make stack of
journals at the back table.
Objective: Learn a specific example of how
Carbon-14 Dating can be used to solve
mysteries.
Responsibilities: Vocab: Radioisotope, Carbon
Dating
Video
https://www.youtube.com/watch?v=YWyi
ZtagxX8
 Take notes on a sheet of scratch paper.
(there will be a writing exercise on
Carbon dating after the video.
 Take notes on the science..
 How is carbon dating done?

Quick Write

How does Carbon-14 Dating work?
12/10
WHOT
Objective: Use your knowledge of radiation to
engineer a radioactivity shield.
Responsibilities:
Quiz this Friday- review notes.
Complete Engineering CER’s.
Stay tuned for the WHOT riddle at the end of class…
Radioactivity! Yikes

What are the first 3 words that come to mind?
Nuclear Reactions
Particle
Symbol
Composition
Charge
Mass (amu)
Shielding
(what will stop it)
Biological
Damage
Alpha
a
Gamma
Beta
0
OR 42𝐻𝑒 b-OR −1
g
𝑒
Notes Radioactivity Notes Review
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Radioactivity is the natural process of atoms falling
apart.
Radioactivity emits both particles and energy as
they transform into more stable atoms.
Common units: Becquerel, (equal to 1 decay per
second), and the Curie, (equal to 37 billion decays
per second), and half life.
We cannot change the rate of radioactivity.
3 types of radiation:
https://www.youtube.com/watch?v=5oUagoF_viQ
Engineering problems!
You have two friends… We will call them Cledus and
Eustace.
Use CER and your knack as an engineer to help them out.
1.
Cledus finds a chunk of strontium-90, a strong Beta
emitter in an old hospital. He got super excited that
he would turn into a superhero if he slept with it under
his pillow. Engineer a solution to save Cledus’s life.
Write in complete sentences. You may include a drawing
or blueprints on your assignment. Turn this in by the end of
class.
Engineering problems!
You have two friends… We will call them Cledus and Eustace.
Use CER and your knack as an engineer to help them out.
1.
Eustace went into his parents wardrobe and came out…
somehow magically… with a plastic box labeled Thorium232. You remember from science class that large elements
are often alpha particle emitters. Design a shield that
Eustace could use to protect himself from his newfound
radioactive material.
Write in complete sentences. You may include a drawing or
blueprints on your assignment. Turn this in by the end of class.
WHOT Q

Create a question about how C-14 dating is used.
 This
should be different than yesterday’s question as
now you have seen how it is used.
WHOT Riddle:
You do not have to copy the riddle… just answer it.
You can use Both Tuesday and Wednesday Boxes to
answer the riddle. You need to explain each
You have three radioactive samples, one alpha
emitter, 1 beta emitter, and 1 gamma emitter. If
you could throw one away, put one in your pocket,
and the put the other in a plastic box; what is the
best choice? Be sure to explain why (use scientific
knowledge).