Half Life

Quiz timeHold up the correct quiz cards for each question... Tip: you may need to hold up more than one!

-

Open your books...Date:Title:

LO:

10/04/23

Half Life

To learn about the rate of radioactive decay, and how we can use it to our benefit.

Don’t forget:Underline the title and date with a ruler!

Outcomes:

You must be able to explain what is meant by radioactive Half-life.

You should be able to give a brief explanation of how radiocarbon dating works.

You could be able to give an example of the limitations of radiocarbon dating.

Question

What do you think is meant by radioactive Half-life?

A radioactive decay graph

Time

Count

1 half life

Throw number Number left

0

1

2

3

4

5

6

7

8

Radioactive decay: Half life experiment

Fill in the number of sweets you start with here.

Don’t eat them yet... That comes in a minute!

Investigation Instructions:

Pour out the sweets onto a paper towel.

The ones showing the sweet logo can now be eaten! (if not by you, then your friend can).

Count the ones left, and write the number in your table.

Now put the remaining sweets back into the cup and start again!

Plot your resultsUsing your table, plot a graph of your results.

25

20

Number 15

of sweets 10

5

0

0 1 2 3 4 5 6 7 8

Throw number

How can we put this to good use?How do we know woolly Mammoths died out 10,000

years ago?

CarbonLiving things on Earth are known as carbon

based life forms.

All living organisms contain carbon.

What are the problems with Carbon dating?

The half-life of carbon-14 is 5,700 years.

If the sample is older than 60,000 years, the amount of carbon-14 is too small to measure accurately.

Samples can become contaminated with materials of a different age which may confuse the readings of carbon-14.

What are the problems with Carbon dating?

Carbon dating anything that died after the 1940s, when nuclear bombs, nuclear reactors and open-air nuclear tests began, is harder to date precisely due to contamination from this increased background radioactivity.

How old is the Turin Shroud?The Turin shroud is estimated to have been

created between 1260 and 1390.

How old is Earth?

One type of Uranium has a half life of 4,500,000,000 years. It decays and eventually becomes lead.

By analysing rock samples it is estimated that the earth is 4,600,000,000 years old.

(Accurate to about +/- 2,000,000 years)

Key Points

The Half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve.

The half-life of carbon-14 used for radiocarbon dating is 5,700 years.

Copy Copy this!this!

Outcomes:

You must be able to explain what is meant by radioactive Half-life.

You should be able to give a brief explanation of how radiocarbon dating works.

You could be able to give an example of the limitations of radiocarbon dating.

Answers1. i) protons

ii) isotopes, protons, neutrons.2. a) i) 400 counts per second

ii) 120 minutes.b)

Radioactivity at work

Dangers of radioactivity

OUTSIDE the body and are more dangerous as radiation is blocked by the skin.

INSIDE the body an source causes the most damage because it is the most ionising.

Alpha

Beta

Gamma

Radiation will ionise atoms in living cells – this can damage them and cause cancer or leukaemia.

The effects of radiationWhen a cell is exposed to radiation it can damage the DNA in the cell nucleus:

Radiation

This cell may then:

repair itself, OR

become cancerous OR

Die

Police probing the death of Russian ex-spy Alexander Litvinenko have found above-normal levels of radiation at three locations in London. Mr Litvinenko's death has been linked to the presence of a "major dose" of radioactive polonium-210 in his body.

The Kremlin has denied UK citizen Mr Litvinenko's claims it was involved.

Mr Litvinenko would have had to either eaten, inhaled or

been given the dose of polonium-210 through a wound. The nature of death as an "unprecedented event in the

UK". Roger Cox from the Health Protection Agency said a large

quantity of alpha radiation emitted from polonium-210 had been detected in Mr Litvinenko's urine.

BBC News – Nov 2006