Presentation on theme: "Matter. Origins of the Idea Democritus (~400 BCE) –Matter is composed of atoms –Atoms are eternal, invisible, indivisible, and incompressible Greeks believed."— Presentation transcript:
Origins of the Idea Democritus (~400 BCE) –Matter is composed of atoms –Atoms are eternal, invisible, indivisible, and incompressible Greeks believed in 3 phases or states of matter –Solid, liquid, gas –We now add plasma as the fourth phase
Matter in the Universe 99% of the known matter in the universe is Hydrogen and Helium The majority of the known matter is in the form of a plasma in stellar interiors The average density of the known matter in the universe is such that 1 gram would occupy a volume 30 x that of Earth The location and characteristics of most of the matter in the universe is unknown – dark matter
Antimatter A matter particle and an antimatter particle are the same with the exception of charge and magnetic properties (which are opposite). Naturally formed and man-made. When matter and antimatter particles collide, they annihilate each other.
Elements Fundamental forms of matter Cant be broken apart by normal means 92 occur naturally on Earth They are the same everywhere
What Are Atoms? Smallest particles that retain the distinguishing physical and chemical properties of an element Made up of subatomic particles: –Protons (+) –Electrons (-) –Neutrons (no charge)
HydrogenHelium electron proton neutron Examples of Atoms
Chemical Bonds, Molecules, & Compounds Bond is union between electron structures of atoms Atoms bond to form molecules Molecules may contain atoms of only one element - O 2 Molecules of compounds contain more than one element - H 2 O
Atomic Number Number of protons All atoms of an element have the same atomic number Atomic number of hydrogen = 1 Atomic number of carbon = 6 6 C 12 6 C 13 6 C 14
Mass Number Number of protons + Number of neutrons Isotopes vary in mass number 6 C 12 6 C 13 6 C 14
Isotopes Atoms of an element with different numbers of neutrons (different mass numbers) Carbon 12 has 6 protons, 6 neutrons Carbon 14 has 6 protons, 8 neutrons 6 C 12 6 C 13 6 C 14
Chemical Origins Most chemical elements were created after the Big Bang in subsequent generations of stars. Nucleosynthesis: primordial (H, He, Li) stellar (He -> Fe) explosive (Co -> …)
Radioisotopes - Radioactivity Have an unstable nucleus that emits energy and particles particles – 2 protons and 2 neutrons particles – an electron rays – a high energy photon Radioactive decay transforms radioisotope into a different element Decay occurs at a fixed rate Because decay happens at a fixed rate, you can use it for age dating! (C 14 has a half-life of 5,700 years.)
The Age of the Solar System Ages of rocks can be measured through radioactive dating: Measure abundance of a radioactively decaying element to find the time since formation of the rock Dating of rocks on Earth, on the Moon, and meteorites all give ages of ~ 4.6 billion years.