C5

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  • Created by: Jess
  • Created on: 27-05-13 14:53
What are atoms within a molecule held together by?
Atoms within a molecule are held together by very strong covalent bonds
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Why do molecular substances have low melting and boiling points?
The forces of attraction between the molecules are very weak, so only a small amount of energy is needed to overcome these forces between the molecules. Hence they have low melting and boiling points.
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Why do pure molecular substances not conduct energy?
Pure molecular substances are not charged so there are no free electrons or ions to conduct electricity
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What is covalent bonding?
Covalent bonding is where atoms share electrons with other electrons so that both atoms have a full outer shell. The atoms bond due to the electrostatic attraction between the positive nuclei and the negative electrons shared between them
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How hydrogen atoms covalent bond?
One hydrogen atom forms a covalent bond with another hydrogen atom so that they each have a full outer shell, as hydrogen only needs one more electron to have a full outer shell
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What is a double covalent bond?
A double covalent bond is when atoms have two shared pairs of electrons e.g. in carbon dioxide
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What is the Earth's hydrosphere?
The Earth's hydrosphere is all the water on Earth e.g. the oceans, lakes, rivers, puddles etc. as well as compounds that are dissolved in water
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What are ionic compounds made of?
Ionic compounds are made of charged particles (ions)
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Why do solid ionic compounds form crystals?
Ionic compounds that have opposite charges are strongly attracted to each other and this causes a build up of ions that forms a lattice. A single crystal of salt is one huge ionic lattice
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Why do molten or dissolved ionic compounds conduct electricity?
Ionic compounds can conduct electricity when they are dissolved or molten as the ions are free yo move in the solution, meaning that they are able to carry an electric current
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Why can't solid ionic compounds conduct electricity?
When an ionic compound is in the solid form the ions aren't free to move, so an electrical current can't pass through the substance
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What is a precipitate reaction?
A precipitate reaction is where two solutions react to form an insoluble solid compound which is called a precipitate
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Which acid can help detect carbonates in a reaction?
You know that there is carbonate, as when carbonates react with hydrochloric acid there will be a fizz as they are giving off carbon dioxide
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How can you test fro carbon dioxide using limewater?
You can test for carbon dioxide with limewater as the carbon dioxide will turn limewater cloudy, this identifies a carbonate ion
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How does using hydrochloric acid and barium chloride test for sulfate?
To identify a sulfate ion, adding HCl followed by barium chloride solution will form a white precipitate of barium sulfate if the original compound was a sulfate (HCl is used to remove any traces of carbonate ions before doing the test)
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How can you test for the presence of halides?
To identify a halide ion, add dilute nitric acid then silver nitrate solution which will leave a white precipitate of silver chloride/ a cream precipitate of silver bromide/ a yellow precipitate of silver iodide
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What is the Earth's lithosphere?
The lithosphere is the Earth's rigid outer layer which is made of the crust and part of the mantle (below the crust) made up of minerals mainly containing silicon, oxygen and aluminium
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What is the covalent structure of a diamond like?
Diamond is made from carbon atoms that each from four covalent very rigid giant covalent structure, which gives diamond a very high melting point
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What are the key properties of diamond?
Diamond is the hardest natural substance, and it does not conduct electricity even when molten, as it has no free electrons. It is insoluble in water
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What is the covalent structure of graphite?
The carbon atoms in graphite form three covalent bonds, creating sheets of carbon atoms which are free to slide over each other, which gives graphite slippery and a useful lubricant
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Why can graphite conduct electricity?
Graphite can conduct electricity and is used for electrodes as only three out of four of carbon's outer electrons are used as bonds, so there are lots of spare electrons meaning electricity can move through graphite
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What are the properties of silicon?
High melting point, doesn't conduct electricity. Similar structure as diamond
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How can metal be extracted from its ore by chemical reduction using carbon/carbon monoxide?
When an ore is reduced, oxygen is removed from it and the carbon becomes oxidised, leaving the metal extracted from the ore
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What is electrolysis?
Electrolysis is the decomposition of a substance using electricity
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What are electrolytes?
Electrolytes are liquids that conduct electricity and are usually free ions dissolved in water (e.g. dissolved salts) or molten ionic compounds
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What are the pros for mining ores?
Mining metal ores is good because useful products can be made; it provides people with jobs and brings money into the area; this means services such as health can be improved
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What are the cons for mining ores?
Mining ores is bad for the environment as it uses lots of energy; scars the landscape; destroys habitats; noise, dust and traffic pollution are caused; deep mine shafts can be dangerous for a long time after a mine has been abandoned
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What are the benefits of recycling metal ores?
There is only a finite about of metal ores; recycling uses less energy than mining and extracting new metal ore; less is put in landfills which pollute surroundings
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Other cards in this set

Card 2

Front

Why do molecular substances have low melting and boiling points?

Back

The forces of attraction between the molecules are very weak, so only a small amount of energy is needed to overcome these forces between the molecules. Hence they have low melting and boiling points.

Card 3

Front

Why do pure molecular substances not conduct energy?

Back

Preview of the front of card 3

Card 4

Front

What is covalent bonding?

Back

Preview of the front of card 4

Card 5

Front

How hydrogen atoms covalent bond?

Back

Preview of the front of card 5
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