14-2 The Formation of Earth Solar system was formed about 5 billion years ago. The sun was formed a couple of million years later then the earth (about 4.6 billion years ago). We know this because scientists have taken core samples around the 1950’s when devices were invented. Earth grew by collision with space debris Volcanoes erupted to form atmosphere 2.2 billion years ago, earth was like it is today

Earth

Radioactive Dating Used to tell age of something Deals with elements (atoms) Atomic number is the number of protons Atoms that differ in the number of neutrons are isotopes

Carbon EX. Regular atom of carbon (C) has atomic number 6 and an atomic mass of 12. This means 6 protons and 6 neutrons. C-14 (carbon 14) also has an atomic number of 6. But the atomic mass is 14. This means 6 protons but 8 neutrons. This fact that it contains more neutrons than normal makes it an isotope.

Half-Life Some isotopes have nuclei which are unstable. These are called radioactive isotopes (radioisotopes). They undergo radioactive decay which means that they release particles of energy. The decay is measured in half-lives. The half-life is the time it takes ½ of the sample to decay. It could be seconds to billions of years.

C-14 Dating

Half-Life EX. Element A has a half-life of 10 years. Given 4g. of element A, explain its half-life. Now: 4g. In 10 years: 2g. In 20 years: 1g. In 30 years: ½g. In 40 years: 1/4g. In 50 years: 1/8g. This shows that the element will never disappear, no matter how much time passes.

Radioactive Dating Most common element used to date materials is C-14. Everything is made of carbon. C-14 half-life is 5,715 years. Used in young dating, below 60,000 years, because it has a short half-life. All elements used in radioactive dating Thorium-230 half-life 75,000 years. Potassium-40 half-life 1,300,000,000 years. Uranium-238 half-life 4,500,000,000 years. The age of the Earth used T-230 and U-238 which is found in rocks.

Radioactive Dating

The First Organic Compounds Found when Earth was first formed. Hypothesis by Oparin (1923). *Atmosphere of the early earth was NH3 (ammonia), H2, H2O, carbon-hydrogen compounds like CH4 (methane). No O2 was present. Also, the gases today are not the same proportions as they were 4 billion years ago.

At temperatures above boiling point of water, these gases formed simple organic compounds like amino acids. Earth cooled, water vapor condensed, formed lakes and seas and the amino acids collected here. These compounds then enter chemical reactions with energy from lightning and ultraviolet rays. These reactions then resulted in macromolecules such as proteins, which are essential to life. (Copy and label Miller and Urey’s apparatus p.267, fig. 14-6).

Miller and Urey

Rise of the First Cells Microspheres are spherical and contain many protein molecules which are arranged as a membrane. Coacervates are collection of droplets that are composed of different types of organic molecules.

Coacervates