Scientist can determine the age of ancient objects by a method called radiocarbon dating. the bombardment of the upper atmosphere by cosmic rays converts nitrogen to a radioactive isotope of carbon, 14c, with a half-life of about 5730 years. vegetation absorbs carbon dioxide through the atmosphere and animal life assimilates 14c through food chains. when a plant or animal dies, it stops replacing its carbon and the amount of 14c begins to decrease through radioactive decay. therefore, the level of radioactivity must also decay exponentially. a parchment fragment was discovered that had about 68% as much 14c radioactivity as does plant material on earth today. estimate the age of the parchment. (round your answer to the nearest hundred years.)

1. Data:

a) Half-life: 5730 years

b) Final radioactivity: 68%

2. Solution:

a) Determine the number of half-lives undergone

b) Compute the time of five half-lives:

c) Round to the nearest hundred:

And that is the age of the parchment.

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.