Carbon-14 is an isotope, with a half- life of 5730yrs, naturally occurring in the air. This means that all living things maintain a fixed ratio of carbon-14 to the stable carbon-12. In a 1g sample there would be 180 000 C-14 atoms. This number starts to drop the moment the living thing stops respiring. a) A 1g scraping of the charcoal from a cave painting in France contained 45000 C-14 atoms.
i) How many half-lives had passed since the tree (that made the charcoal) was felled?
if) When was the painting made?
b) For many years it was believed that the Romans were the first to introduce grapes to
Britain. A 0.02g grape pip found at the British hillfort of Hambledon Hill contained 1800 C-14 atoms.
i) How many C-14 atoms would there have been in 1g of grape pip?
ii) How many half-lives had passed since the grape was picked?
iii) How long ago was the grape picked? iv. What evidence does this give for the introduction of grapes to Britain?