Essay on Chemical Earth AZ

Submitted By fjakslhfodidhfad
Words: 847
Pages: 4

Chapter 1
Matter - Anything that has mass and occupies space
- Can exist in liquid, solid and gaseous states

SOLID
LIQUID
GAS
SHAPE
Definite
Variable
Variable
VOLUME
Definite
Definite
Variable
COMPRESSIBILITY
None
Medium
High
DIFFUSION
Negligible
Slow
Fast
PARTICLE
ARRANGEMENT
Closely packed,
Fixed positions
Fairly closely packed, not fixed positions (slip/slide)
Widely spaced,
Move independently
THERMAL EXPANSION
Small
Moderate large Kinetic Theory
Gas
Composed of molecules
Molecules widely spaced and move in rapid, random motion
Movement results in collisions, perfectly elastic
Kinetic energy of molecules increases with temperature
Elements – pure substances that cannot be separated by chemical change into simpler substances
Compounds – pure substances composed of two or more elements chemically combined in fixed proportions
Mixtures - two or more substances mixed together in variable proportions
Homogenous
Uniform composition and properties throughout
Heterogeneous
Variable composition and properties throughout

Earth
Layered structure -> core, mantle, crust
Solid lithosphere, Liquid hydrosphere, Gaseous Atmosphere
Spheres consist of mixtures of elements and compounds

SEPERATION TECHNIQUES
Filtration
undissolved solid and liquid or gas passing mixture through a filter
Solution
one substance dissolves more readily in a solvent than the other
Evaporation
dissolved substance, liquid different volatilities of substance
Crystallisation
dissolved substance in liquid different solubilities, crystallise separately from solution
Centrifugation
different densities or different states spinning motion is used to separate components of a mixture
Decantation
liquid poured off from solid
Sieving
different particle sizes
Distillation and Fractional Distillation different boiling points boiling and condensing
Chromatography
liquid or gas passing over substance which components absorb with different strenghts

Qualitative Analysis identifying components
Quantitative Analysis the amounts of the components, % composition
Gravimetric Analysis quantitative carried out by weighing

Signs of Chemical Reactiosn new substance produced colour change temperature change gas produced/bubbles precipitate formed sound, light, heat energy…
Often reversible

Chapter 2 all of the compounds and mixtures found on Earth are combinations of the elements iron and then oxygen are the most abundant elements on Earth hydrogen and helium are the most abundant in the universe the reactivity of an element determines its occurrence in nature – less reactive elements, eg. Gold, can be found in their pure forms
- more reactive elements, eg. Sodium, actively combine and are rarely found in their pure form Physical Properties - > determined without changing the chemical composition used to classify as metal, non-metal and semi-metal all elements have a wide range of properties and there are always exceptions to the classification
(generally)

PROPERTY
METALS
NON-METALS
SEMI-METALS
MELTING POINT
Usually high
Usually low
High
BOILING POINT
Usually high
Usually low
Usually high
ELECTRICAL CONDUCTIVITY
High
Very low
Low
HEAT CONDUCTIVITY
High
Very low
Low
APPEARANCE
Lustrous
Usually no lustre
Variable
EXAMPLES
Aluminium, sodium
Carbon, chlorine
Silicon, arsenic

The physical properties of an element determines its uses.

Chapter 3:
Atomic Theory a single representation of an element consists of a nucleus surrounded by electrons
Nucleus
contains positive protons and neutral neutrons small in relation to size of atom contains over 99.9% of the atoms mass extremely dense positive charge (equal to the number of protons)
Electrons
negative charge surround the nucleus in energy levels
Electron Configuration
2, 8, 18, 32…
After the second level 8 electrons in the outermost…