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PRESENTATION

GEORGE SIDERIS, NIKOS KLIAFAS

8. Thanks

4. Dating the Age of Rocks

2. Half-Life of carbon-14

6. Living VS Non-Living Matter

5. Video

INDEX

Chapter 01

Radioactive dating consists of a variety of methods that use radioisotopes to measure the age of minerals and organic matter. The most common method is radiocarbon dating, which is used to find the age of organic matter, which originated from trees and animals. There are also techniques that find the age of inorganic materials like rocks and minerals.

Chapter 2

Half-Life of carbon-14

The half-life of carbon-14 is 5600 years. Carbon-14 can be found in dead plants or animal materials. When carbon-14 reaches its half-life that means that the carbon-14 that is found on the dead plants or animal materials will also halve. In case to estimate the amount of carbon-14 in a sample that is found we are measuring the activity of the sample. The activity of carbon-14 that is found compared with the amount of carbon-14 that would have been present when the sample was part of a living organism it is possible to estimate when the source of the sample died.

HALF-LIFE OF CARBON-14

Chapter 3

The first thing we should do is to find the half-life of the Bq:6 Bq = 24 : 2 : 2Since the activity of the sample has halved twice from that expected in living wood, two half-lives must have passed Finally, the age of the sample must be:2 x 5600years = 11.200 years

120 g of living wood has a radioactive activity of 24 Bq (Becquerel). A 120 g sample of wood from an historical site is found to have an activity of 6 Bq. If the half-life of carbon-14 is 5600 years, estimate the age of the wood from the site.

How to estimate the age of wood

Chapter 4

Dating the Age of Rocks

As non-living matter like rocks cannot absorb carbon-14 (which is used in radiocarbon dating) alternate techniques are used. When a radioactive substance decays it transforms into a different element, which can be of the same or a different element. The original radioisotope is the parent nuclide and the new radioisotope is the daughter nuclide. Both the parent and the daughter isotopes decay. When the parent isotope decays it creates a decay series which consists of different elements. The decay series ends when a stable isotope is created, or one that cannot decay further.

DATING THE AGE OF ROCKS

So as to find the age of rocks we measure the proportion of parent nuclides to stable daughter nuclides. The half-life of most radioactive parent isotopes is extremely long, in some cases greater than the lifetime of earth. For example the half-life of potassium-40 is 1.25 billion years, and the decay series ends with argon-40.

DATING THE AGE OF ROCKS

Chapter 5

Video

VIDEO

Chapter 6

Living VSNon-Living Matter

• They don't have carbon-14
• They aren't made up of cells
• They don't have a definite life cycle
• They don't require food, air and water
• They respond to changes around them
• They don't grow

non-living matter

• They have carbon-14
• They are made up of living cells
• They have a definite life span after which they die
• They require food, air and water
• They respond to changes around them
• They grow

Living matter

VERSUS

Chapter 7

Radiocarbon dating measures the level of an isotope called carbon-14, which is made in the atmosphere. Cosmic rays from space have a lot of energy, which when it hits the atoms of gas in the atmosphere it breaks apart the nuclei. The parts of the broken nuclei travel at high speeds and if they hit other atoms a nuclear transformation happens. The nuclear transformations turn the elements in the air into different isotopes. One such transformation is when a fast-moving neutron collides with an atom of nitrogen. The result of that collision is that the nitrogen atom transforms into an atom of carbon-14.