Matter,minerals and rocks |
Matter
What is the Earth made up of? Matter, of course, but what is matter?
Elements and atoms
Matter can be broken down into 92 elements. Elements are "species"of matter. But how does one element differ from another? All matter is made up of atoms and the 92 elements are the 92 different types of atoms that can exist.How is an atom of one element different from another?
Nucleus - protons +neutrons surronded by electrons
Atomic no = #P (=no of electrons)
Mass Number = Atomic weight = #P+#N
Atomic number is what controls the chemistry as it controls the no and confuration of electrons
eg. hydrogen one P, therefore mn=1, an= 1
sodium 11 P, 12 N, therefore an= 11 mn 23.
Carbon 6P , 6N
Isotopes
Atoms of an element must have same no of P, but can have different N. These are the isotopes of the element. Isotope identified by its mass number
eg. carbon
Carbon 12: 6P + 6N
Carbon 13: 6P + 7N
Carbon 14: 6P + 8N
Atomic weight given as 12.011 reflects that there are very few atoms of 13 & 14
Compounds and Chemical reactions - atoms combine
Elements are rarely fond alone in nature - gold, silver, copper, iron, sulphur, carbon, oxygen, nitrogen + few other gases
Most substances formed as a result of two or more elements combining to form a compound
Groupings of atoms together called a molecule
Chemical Bonds
Electrons arranged in shells that have only a certain number of slots or spaces for electrons. Some atoms may have one or two electrons and not a full shell. More conveneient too strip away electon to form an ion - an electrically charged atom. (+) Cation
In other atom outer shell not completely filled and one or two slots open atom more stable of these filled to form a negative ion (-) Anion
If first meets second it means that elecrons can go from one to the other, then oppostite elecrical charge holds them together - chemical bond (ionic, in this case) electron transfer
Electron sharing can occur - covalent bond.
Other factor if the size of the ion : ionic radius
States of matter: Gases, liquids and solids
Gas - altoms or molecules moving so fast that will fly by each other without making a bond
Liquids - bonds from, break and reform with another atom - "promiscuous"
Solid - bonds are permanent. Two kinds of solid - amorphous different species of atoms in no special position relative to another - crystalline atoms arranged in organized structure (DNA etc). external form of a crystal reflects the internal organization of atoms
Transformation of solid -> liquid -> gas and vice versa
MINERALS
Naturally occurring, usually inorganic, crystalline solid with a definite chemical composition
Crystal shape reflection of internal atomic structure, also controls its properties
Structure determined using X-rays
How do minerals crystallize?
- from a melt, by cooling of a moltem solid
- from solution
- in a living cell eg calcite, apatite (Ca phosphate)
- recrystallization - from previous mineral or set of minerals
Mineral groups
Minerals can be grouped according the chemical compostion. Most are a metal (cation) + anion, examples
carbonate -CO3, silicate, sulfide etc
The rock forming minerals
These are the minerals and mineral groups that are the most common that make up rocks:
Compositon of the Earths Crust
Oxygen (O) 46
Silicon(Si) 28
Aluminum(Al) 8
Iron (Fe) 6
Magnesium(Mg) 4
Calcium (Ca) 2.4
Potassium(K) 2
Sodium(Na) 1
+ in oceans and amosphere Carbon (life) hydrogen, more oxygen, sulfur
Most common mineral groups:
silicates, oxides, carbonates, sulphides, sulphates
Silicates
Silica tetrahedron
Silicate subgroup: isolated, rings, single chains, double chains, sheets, frameworks
Physical properties of minerals
This is the way we can easily distinguish one mineral from another without complicated chemical or x-ray analysis
Habit
Luster
color/streak hematite id silvery looking, dark red streak
hardness - Mohs scale
- Tall girls/guys can flirt and other queer things can do
talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz,topaz, corundum, diamond
Fingernail penny knife glass
Cleavage/fracture
Density
Tips on identifying minerals
ROCKS - AN INTRODUCTION (CH3)
Rocks are ggregates of mineral grains
xtallization: melt igneous
solution sedimentary
living cells "
recrystallization metamorphic
Igneous:
volcanic - fine grained; plutonic - coarse grained
Sedimentary rocks
Pre-existing rocks eroded, particles or solution, carried to sea by rivers, or wind
Particles accumulate in sea - clastic; or ppt by organisms, chem reactions (ppt from solution) lithified
Sedimentary rocks are layered (bedded)
Metamorphic rocks
caused by change of temperature pressure conditionsthat the rock experiences
Heating near a pluton - contact metamorphism, buried by tectonic processes - regional metamorphism
Rock cycle
Diagramatic representation of these processes that converts one type of rock to another