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Human Biology Year 12 > Potassium argon dating - Absolute dating > Flashcards

Potassium argon dating - Absolute dating Flashcards

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1
Q

What is dating?

A

Determining the age of the fossil or artifact.

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2
Q

What is absolute dating?

A

Gives the actual age of the species in years.

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3
Q

What is relative dating?

A

Tells us whether one sample is younger or older than another.

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4
Q

What are the 3 methods of absolute dating?

A
  1. Potassium argon dating.
  2. Radiocarbon dating.
  3. Dendrochronology.
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5
Q

What is potassium argon dating?

A

Is based on the decay of radioactive potassium to form calcium and argon. The more calcium and argon the older the rock.

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6
Q

How old can the method of potassium argon dating date rocks too?

A

Date rocks aged older than 100,000 to 200,000 years old.

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7
Q

What does potassium argon dating only date?

A

Rocks.

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8
Q

What are the 3 isotopes of potassium is a mixture of?

A
  1. Potassium -39.
  2. Potassium -40.
  3. Potassium -41.
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9
Q

What is an isotope?

A

Are atoms of the same element with different numbers of neutrons.

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10
Q

How many protons do all isotopes of potassium have?

A

All have 19 protons.

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11
Q

How many neutrons does potassium -39 have?

A

20 neutrons.

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12
Q

How many neutrons does potassium -40 have?

A

21 neutrons.

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13
Q

How many neutrons does potassium -41 have?

A

22 neutrons.

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14
Q

What does potassium -40 decay to?

A

Decays to form argon -40 and calcium -40 at an extremely slow but constant rate. As the rock ages, the proportion of potassium -40 decreases while that of argon -40 increases. Determining the amounts of potassium -40 and argon -40 in a rock sample can be used to calculate the age of the rock.

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15
Q

What can determining the age of the rock be used for?

A

Can be used to predict the age of fossils found in that rock.

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16
Q

What is the half-life of potassium -40?

A

1.25 billion years.

17
Q

What is a half-life?

A

The time required for half of any quantity of radioactive material to decay into stable non-radioactive material.

18
Q

What are the 3 limitations of potassium argon dating?

A
  1. Not all rock types are suitable for this method of dating.
  2. Rocks must be older than 100,000 to 200,000 years.
  3. Detection devices cannot detect very easily.

Human Biology Year 12 (104 decks)

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