Flashcards in Chemistry 5: Chemicals Of The Natual Environment Deck (65)
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1
Dry air
Air that has all water vapour removed
2
Name the formula and the percentage of dry for nitrogen oxygen all gone and carbon dioxide
Nitrogen, N₂, 78%
oxygen, O₂, 21%
argon, Ar, 1%
carbon dioxide, CO₂, 0.04%
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Covalent bonds
These joined together the atoms inside a molecule
4
How does a covalent bond form
1. A covalent bond forms when atoms share a pair of electrons.
2. The atoms are held together because the positively charged nuclei of both atoms attracted to the negative charge a pair of electrons
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Simple molecular substances
Simple molecular substances, such as molecules in the air, have a very low melting points and boiling points
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Name the melting point and boiling point of nitrogen and oxygen
Nitrogen: melting point = -210°C, boiling point = -196°C
Oxygen: melting point = -218°C, boiling point = -183°C
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Why are the mounting am boiling point slow in simple molecular substances
The melting points and boiling points all day because the attractive forces between small molecules are very weak. Very little energy is needed for molecules to overcome these forces move apart
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Can pure molecular substances conduct electricity?
Molecules of elements and compounds have no electrical charge, soap your molecular substances cannot conduct electricity
9
Describe the forces between small covalent molecules and when they melt
1. For small covalent molecules, the forces between molecules are weak, but the fault is with the molecules (covalent bonds) are strong
2. When a molecular substance melts, the molecules are easily separated from one another but the molecules themselves are not broken up into separate atoms
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Hydrosphere
Made up of water, ice and snow on the earth surface and water vapour in the atmosphere
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What is the earths hydrosphere
The earths hydrosphere is all the water and Earth, including oceans, seas, legs and rivers. The hardest bit is mostly water, with some dissolved compounds called salts
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Ionic compounds
Salts made up of particles called ions which have a positive or negative electrical charge
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What are salts
Salts are ionic compounds. Irons have either a positive or negative charge and I arranged in a giant 3-D pattern called a lattice
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Ion
Atom (or groups of atoms) with a positive or negative charge, caused by losing all gaining electrons
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Lattice
A repeating pattern and phoned by the regular 3-D arrangement of ions
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Ionic bond
Chemical bond between two ions of opposite charges
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What are the properties of an ionic compound
1. Ionic compounds have high melting and boiling points because a large amount of energy is needed to overcome the forces between ions in the lattice
2. Ionic compounds you're not conduct electricity when solid, because The ions are not free to move.When they are melted or dissolved in water, the ion can move and they conduct electricity
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Describe the formula of an ionic compound give an example
In the formula of an ionic compound, the number of positive charges just balance cancel out the negative charges, e.g. Na^+ and Cl^- make NaCl; Mg²+ and Cl make MgCl₂
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Molecular ion
A charge ion composed of two or more atoms joined together by covalent bonds
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Given example of a molecular ion
SO²₄^-
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How do we test for ions
1. Ions in a compound can be identified by their distinctive properties, for example compounds containing the copper ion are often blue
2. Solutions of some ionic compounds make the precipitate of an insoluble compound when they mix. The colour of the precipitate can be used to identify the ions in the compound
3. Adding an alkali, such as dilute sodium hydroxide, to different positive metal ions gives different colours of precipitate
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How are negative carbonate ions identified
1. Negative carbonate ions are identified by adding dilute acid and looking for fizz (effervescence)
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How are negative hydroxides ions identified
Negative chloride, bromide, iodide and sulphate ions are identified by adding dilute silver nitrate or dilute barium chloride and looking for participates
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Why do carbonates fizz when an acid is added?
Carbonates fizz when an acid is added because carbon dioxide gas is made in the reaction
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When do participates form
Precipitates form when an insoluble solid is made in the reaction. For example, most mental hydroxides are insoluble, as is silver chloride from the reaction of silver ions and chloride ions
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Give examples of ionic equations with state symbols. Positive ions reacting with hydroxide ions. Negative ions reacting with silver or barium ions.
1. For positive ions reacting with hydroxide ions: Cu²^+ (aq) + 2OH^- (aq) ➡️ Cu(OH)₂ (s)
2. For negative ions reacting with silver ions or barium ions: Ag^+ (aq) + Cl^- (aq) ➡️ AgCl (s)
27
What is the outer layer of the earth
The lithosphere is the rigid outer layer of the earth, made up of the crust and the upper mantle. It contains rocks and minerals
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How are minerals arranged?
Minerals are solids with atoms or ions arranged in a regular arrangement or lattice, e.g. carbon in the form of diamond or lattice
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Give examples of abundant elements in the earths lithosphere
1. Silicon, oxygen and aluminium are very abundant elements in the earths lithosphere
2. Most of the silicon and oxygen in earth are joined together in earth's crust as silicon dioxide, e.g. In the mineral Quartz
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What are ores?
Rocks that contain metal minerals
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What do some ores contain
Some ores contains metal oxide
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Name elements that can be extracted from their ores and their amounts
1. Copper, zinc and iron can be extracted from their ores by beating their metal oxides with carbon. Carbon reduces the metal oxide by taking away oxygen
2. The amount of minerals in ores varies. For some metals e.g. copper, a huge amount of Rock has to be mined to extract a small amount of metal
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Redox reaction
The reaction for extracting metals from their ores, involving both oxidation and reduction
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Reduction
Process that reduces the amount of oxygen in a compound, or removes all the oxygen from it- the opposite of oxidation
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Oxidation
Chemical process that increases the amount of oxygen in a compound; the opposite of reduction
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Name the word and symbol equation of zinc oxide +carbon and describe what has happened in this reaction
Zinc oxide + carbon ➡️ zinc + carbon dioxide
2ZnO (s) + C (s) ➡️ 2Zn (s) + CO₂
In this reaction the zinc has been reduced and carbon has been oxidised
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Giant covalent structure
An element made with very strong covalent bonds between atoms in which a large number of carbon atoms are linked together in a regular pattern
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Give an example of a giant covalent structure
1. Diamond and graphite contain many carbon atoms covalently bonded to get her in a regular pattern
2. Silicon dioxide also has a giant covalent structure, so it's has similar properties to a diamond
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When do covalent bonds form
Covalent bonds form when atoms share electrons
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What are the properties of a diamond
1. The bonds in diamond are very strong and need a large amount of force to break them
2. This is why a diamond has a very high melting and boiling points and does now dissolve in water
3. There are no free charged particles in a diamond, so it does not conduct electricity when charged or when melted
4. In a diamond, each carbon atom is covalently bonded to four other atoms in a tetrahedral 3-D lattice
41
What are the properties of graphite
1. In graphite, each atom is strongly bonded to three other sheets.
2. The sheets are strong but these is only a weak force between the layers, so they can slide over each other
3. There are the free-moving electrons between the layer in graphite, so it conducts electricity
42
What do we HAVE to REMEMBER about covalent and ionic bonds
1. Ionic compound contains CHARGED PARTICLES and so electricity when they are molten.
2. Covalent compound me have NO charged particles and cannot conduct electricity
3. Graphite is the ONLY EXCEPTION to this rule
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Relative atomic mass (RAM)
The mass of an atoms compared to the mass of the atom of carbons (which has a value of 12)
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Relative formula mass (RFM)
The sum of the RAMs of all the atoms and ions in a compound
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Gram formula mass
The number of grams of an element or compound represented by its RAM or RFM
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What is the formula for finding the percentage of metal in minerals
percentage of metal in minerals = (total mass of metal atoms/ gram formula mass) x 100
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Electrolysis
Decomposing an ionic compound by passing an electric current through it while molten or in solution
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Electrolyte
The liquid in which electrolysis takes place
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What happens to electrolytes when electricity passes through it
Electrolytes break down, or decompose, as the electricity passes through
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How is aluminium extracted from aluminium oxide
Aluminium is extracted from aluminium oxide by electrolysis. Aluminium and oxygen are made in this process
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Why is electrolysis used to separate metals like aluminium
Electrolysis is used to extract more reactive metals (e.g. Aluminium) because their oxides can me be reduced by carbon
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How do metals form at the negative electrodes and give an example for chloride and oxide
1. Metals form at the negative electrode because positive metal ions are attracted to the negatively charge electrode (cathode)
2. Negative ions such as chloride (Cl^-) and oxide (O^2-) moved to the positively charged electrode (anode).
3. Non-metals such as chlorine and oxygen form at the anode
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Cathode
Negative electrode
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Electrodes
Solid electrical conductors through which the current passes in and out of the liquid during electrolysis- and at which the electrolysis reactions take place
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Anode
Positive electrode
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What happens do the electrons at the negative electrode and give examples
1. At the negative electrode, metals ions gain electrons and become neutral metal atoms, e.g. aluminium ions gain 3 electrons to form aluminium atoms: Al^3+ + 3e- ➡️ Al
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What happens do the non-metal ions at the positive electrode and give examples
At the positive electrode, non-metal ions lose electrons and become neutral non-metal atoms, e.g. 2 oxygen ions lose 2 electrons each to form oxygen gas: 2O^2- ➡️ O₂ + 4e-
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Why are metals useful
Metals are very useful because they are very strong, malleable (they can be hammered into shape), have high melting point and are good conductors of electricity
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Metallic bonds
The force in metals that attracts that attracts atoms together they are strong so a lot of energy is needed to melt or reshape them
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How is a 'sea of electrons' created
Metal atoms lose their outer-shell electrons to form positive ions. In solid metals, the outer-shell electrons form a 'sea of electrons', which can move freely
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What does the attraction between positive ions and the sea of electrons mean
1. The attract between the positive ions and the sea of electrons is very strong, so the metals have high boiling point and high strength
2. Metals conduct electricity because the electrons can move.
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What happens on pure metals
1. In pure metals, all the atoms are the same size and can roll over each other
2. This means that metals can be reshape do (they are malleable) even though the bonds are strong
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What do we need to remember about how metals and ionic compounds conduct electricity
1. Metals and ionic compounds conduct electricity in different ways.
2. Ionic compounds ONLY conduct when they are MOLTEN or in a solution because the ions need to MOVE
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Give examples of poisonous metals
Lead, mercury and cadmium
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