Atoms, Elements and Compounds
Mixtures can be separated into simpler substances with fewer parts.
A comppound can be broken down into simpler compounds or its elements.
Elements are substances that cannot be broken down by chemical reactions into simpler substances.
Symbols are not always the letters of the element.
Inside the Atom
Sub-atomic particles have both a charge and a mass.
Since an atom has an equal number of protons/electrons, the charges cancel each other out.
Neutrons hace no charge.
The electronic configuration of an atom gives the number of electrons and arrangement of the shells.
Each shell can hold a certain amount of electrons.
The periodic table lists all known elements by increasing proton number.
It has horizontal rows (periods) an vertical columns (groups).
The group no. tells you how many outer electrons the atom has.
Atoms with fewer than 8 outer electrons will react in a way to give them a full outer shell.
When methane burns, the atoms in methane an oxygen react an turn into CO2 and H2O
This does not account for all the reactan atoms as products.
This is the balanced equation, it whos what happens with all the atoms.
Calcium hydroxide solution (limewater) is used to test for CO2. If CO2 is present, the solution turns cloudy.
Cement is made by heating limestone and clay
Mortar is made by mixing cement, sand and water.
Concrete is made by mixing cement, sand, gravel and water.
Metals from Ores
Some ores are metal oxides, they can be smelted directly.
At the smelter the ore is crushed to remove rock.
To convert the metal oxide to metal, the oxgen must be removed. This is called reduction.
Iron ore, coke and limestone are are fed in at the top of the furnace. Molten iron and **** are collected at the bottom.
Metal atoms are arranged in giant structures in regular rows an layers.
Metals are able to bend as the layer slide over each other.
Metlas conduct electricity as they have free electrons.
to make metals stronger, they can be mixed to form alloys.
Iron and Steel
Pure iron is too soft for most uses, so instead, steels are used.
Adding other metals to molten steel can give it special properties.
For example chromium an nickel can give the steel a higher resistance to corrosion.
Manganese can give steel more strength and more hardness.
Stainless steel is about 70% iron, 20% chromium and 10% nickel.
Copper is purified via electrolysis.
Electricity is passed though a copper sulfate solution. This is called electrolysis.
Copper atoms in the impure posotive electrode lose electrons.
At the pure copper negative electrodes, copper ions in the solution gain electrons.
Aluminium can only be extracted via electrolysis.
Titanium cannot be extracted by carbon or electricity. The ore, rutile is converted to titanium chloride and is then reacted with magnesium.
Metals and the Environment
Mining metal ores destroys the landscape, habitats etc.
Using carbon to reduce ore produces CO2
Smelting ores produces sulfer dioxide (SO4). This can cause acid rain.
Recycling aluminium/steel saves energy and the environment. Aluminium cans are cleaned and melted before re-use.
Brownfield sites are areas that have been used before. They are often polluted by toxic metal compounds.
A Burning Problem
Global warming is increasing the CO2 in the atmosphere whcich traps more energy from the sun, making the earth heat up.
Golbal dimming is where dust particles in the air prevent sunlight reaching the ground, this reduces the energy available for photosynthesis.
Acid rain is caused by nitrogen, sulfer and CO2 dissolving in rain water.
The adic rain formed attacks limestone buildings much more quickly than normal rain. It also damages trees and can harm aquatic life.
Reducing Air Pollution
Vehicles that burn fossil fuels produce poisonous carbon monoxide, they also produce nitrogen oxides that can cause acid rain.
To reduce the mount of these comounds released by vehicles all new cans have catalytic converters fitted.
Alternative fuels are also being made, like biodiesel made from vegetables.
These contain almost no sulfer
When crude oil is heated to about 400 degrees most of it boils and evaporates
Vapor consisting of hydrocarbons rise up the column, gradually cooling.
Hydrocarbons with high boiling points condense first. The lower the BP, the higher up the column they rise before the condense.