C5-Chemicals of the natural atmosphere

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  • Created by: Naana
  • Created on: 30-05-14 13:17
Name a gas in dry air that is a compound
Carbon dioxide (co2)
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What are elements?
When the molecules only contain one type of atom
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What are compounds?
When the molecules contain more than one type of atom bonded together
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Why are most gases molecular substances?
Because you only need a little bit of energy to overcome the weak forces between the molecules and so they have low melting and boiling points
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Why don’t molecular substances conduct electricity?
Because the molecules aren’t charged. There are no free electrons or ions
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What is covalent bonding?
This is when an atom shares electrons with other atoms. This ensures that both atoms have a full outer shell as the covalent bond provides one extra shared electron for each atom.
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Why do atoms bond?
The bonding is due to the electrostatic attraction between the positive nuclei and the negative electrons shared between them.
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What is the earth’s hydrosphere?
This consists of all the waters in the oceans, seas, lakes, river, puddles and so on. It also contains any compounds that are dissolved in the water.
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What makes sea water salty?
The ionic compounds called salts that dissolve in the water
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Why do solid ionic compounds form crystals?
Ionic compounds are made of charged particles called ions. Ions with opposite charges are strongly attached to one another, which cause giant lattice of ions to build up. One giant ionic lattice forms a salt crystal.
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Do solid ionic compounds have low or high boiling points? Explain
Ionic compounds have high boiling points because the forces of attraction between the ions are very strong and so it takes a lot of energy to overcome these forces and boil it. Solid at room temp
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Why can ionic compounds conduct electricity when dissolved in water or molten but not when they’re solid?
Because when an ionic compound dissolves in water or melted, the ions separate and are free to move in the solution which means that they carry an electrical current, which can pass through the substance.
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What characteristic colours do sodium, potassium, calcium and copper compounds give when heated?
Sodium=orange/yellow flame, potassium=lilac flame, calcium=brick red, copper=blue-green flame
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How do you test for carbon dioxide?
Bubble the carbon dioxide through a test tube of limewater. If the limewater turns cloudy you have identified a carbonate ion.
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How do you test for sulphates?
You use a dilute hydrochloric acid to get rid of any traces of carbonate ions which would also produce a precipitate, followed by barium chloride solution. A white precipitate of barium sulphate means the original compound was a sulphate.
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How do you test for halides?
You use dilute nitric acid to get rid of any carbonate ions before the test so the results are not confused, followed by silver nitrate solution.
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What colour precipitates do solutions containing chloride, bromide and iodide ions produce in the halide test?
Silver chloride is a white precipitate; silver bromide is a cream precipitate and silver iodine is a yellow precipitate.
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What is the Earth’s lithosphere?
The lithosphere is the earth’s rigid outer layer-the crust and part of the mantle. It is made up of a mixture of minerals containing silicon, oxygen and aluminium.
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What are the properties of diamond?
Insoluble in water, doesn’t conduct electricity as it has no free electrons, has very high melting point and is the hardest natural substance due to strong covalent bonds
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Why does graphite conduct electricity?
Because only 3 out of each carbon’s 4 electrons are used in bonds, so there are lots of spare electrons which are free to move around and carry an electric current.
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What is a metal ore?
They are rocks that contain varying amounts of minerals (solid elements and compounds) from which metal can be extracted
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What metals can be extracted by reducing its oxide with carbon?
Iron oxide, zinc oxide and copper oxide
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What is electrolysis?
This is the decomposition (breaking down) of a substance using electricity
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What are electrolytes?
They are usually free ions dissolved in water or molten ionic compounds
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During electrolysis what happens to the electrons?
Electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode. As ions gain or lose electrons they become atoms or molecules.
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What do the terms reduced and oxidised mean?
When a metal oxide loses its oxygen it is reduced. When carbon gains oxygen it is oxidised.
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Why are metals able to conduct electricity?
Because there are free electrons which come from the outer shell of every metal atom ion the structure. And these free atoms can move freely and can carry electrical current through the material making metals good conductors of electricity.
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Why have metals got high melting and boiling points?
Because metallic bonds are very strong and so it takes a lot of energy to break them apart.
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Ores are finite. What does this mean?
This means that there is a limited amount of ores. Eventually, they will run out.
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Why is mining ores good?
Useful products can be made, provides local people with jobs and brings money into areas so that public services such as transport and health can be improved.
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Why is mining ores bad for the environment?
Uses a lot of energy- most of which comes from fossil fuels, scars the landscape and destroys habitats
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Give 2 reasons why it is good to recycle metals
Recycling metals only uses a small fraction of the energy needed to mine and extract new metals, which saves money. Also, it cuts down on the amount of rubbish sent to landfills, which take up space and pollute surrounding areas.
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When the molecules only contain one type of atom

Card 3

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What are compounds?

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Card 4

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Why are most gases molecular substances?

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Card 5

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Why don’t molecular substances conduct electricity?

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