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40 Cards in this Set
- Front
- Back
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What is an element |
An element is a pure substance that cannot be broken down into simpler substances by chemiscal methos. It only has one type of atom in it molecule. |
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Difference between metals and non-metals :
1) Surface 2)Electricity 3) heat 4) "Quality" 5) Sounds
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MEATALS
1) Good conductors of electricity 2) Good conductors of heat 3) Shiny surface that reflects light 4) Malleable and ductile , can be hammered into shapes or drawn into wire easily. 5) Sonorous ( capable of producing sounds )
NON-METALS 1) Does not conduct electricity 2) Poor conductors of heat 3) Dull surface 4) Brittle and breaks easily when force is applied 5) Nom-sonorous |
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Compounds are |
Fromed when two or more elements combine together in a chemiscal reaction. |
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How can compounds be decomposed into its constituent elements. |
Compounds can only be decomposed into its constituent elements by chemical methods |
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Properties of compounds |
are different from its constituent elements .
Because bonds between atoms and then intermolecular forces have chnaged. |
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The basic unit of a compound is a molecule. A pure compound... |
Consist of one type of molecule and has a fixed boiling and melting point
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Mixtures are formed when |
two or more substances are mixed in any ration without chemiscal reaction |
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MIxtures of elements and compounds are ... |
not pure as they contain more than one type of atom or molecule |
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A mixture boils and melts... |
over a range of temperatures |
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A mixture has variable ... |
compositions |
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A mixture can be separated into its constituent substances by |
physical methods |
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A mixture will have the properties of... |
all the substances it consists of because these substances have not been changed in any chemical reaction and will continue to exhibit their properties |
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Chemical bonds are known as |
The forces that bind atoms together in a molecule |
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What is a lattice structure |
The arrangement of particles in a fixed pattern in a solid |
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what are the 4 different types of structures you have learnt |
Ionic Simple molecular Giant Molecular Metallic
Structure |
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the gases are very stable in what group and why |
Group 0 , as their valence shell is completely filled with electrons |
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Atoms try to achieve the noble gas configuration because |
they want to be stable |
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Ionic bonding is formed between |
Positiove ions of metaals and negative ions of non-metals. |
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Each ion is surrounded by
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6 other ions |
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Ionic compounds has ___________ mp and bp |
high |
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Describe in term of arrangement of ions why ionic compounds have high melting and boiling points. |
The ions are held together by strong electrostatic forces of attraction . Hence these lattices are very strong and stable.
Alot of heat energy is required to overcme theese bonds . Hence ionic compounds have high melting and boiling point |
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How strong an ionic compound can be depends on ...
how it affects the temperature |
The charges of the positive and negative ions. The higher the charges of ions , the stronger the ionic bonds .
Hence The stronger the electrostatic forces of attraction between ions and larger amounts of heat energy is needed to overcome these bonds
Hence MP and BP inceases |
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Ionic compounds are good for
WHY? |
refractory materials ( heat resistant materials )\
- Lining of furnaces ( MgO)
Because they have a high MP and BP |
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Ionic compounds conduct electricity only when |
they are molten or in aqeous solution. They do not conduct electricity in solid state |
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Why ionic compounds cannot conduct electricity in solid state |
In solid state , it does not have any mobile ions to move about and conduct electricity. |
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When ionic compounds are melted , |
The heat energy supplied weakens the ionic bonds between the ions and they break free from the structure. They are now free to move about within the molten ionic compound and can conduct electricity. |
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Most ionic compounds are soluble in _____________ but not soluble in ________________ |
Water
but insoluble in organic solvents. |
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Ionic compounds are solids in |
room temperature |
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Criteria for a compound to conduct eectricity |
1) Contains charged particles 2) They are mobile |
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Covalent bonds are usually formed between atoms of |
non-metals only |
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Forces between molecules in covanet bonds are |
wear van der waals' forces of attraction
hence their mp and bp are low |
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covalent bonds within molecules in convalent bonds are weak/strong ? |
Strong |
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covalent bonds between molecules in convalent bonds are weak/strong ? |
weak |
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covalent compounds are usually , what type of liquids and gases ? |
Volatile liquids and gases duee to their low bp and mp. They evaporate easily.
Eg ( perfumes ) |
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Covalent compounds are insoluble in _________and soluble in ______________ |
Water
but dissolves in organic solvents |
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Covalent comppounds in terms of electricity conductivity ... |
they do not conduct electricity as they do not contain ions within their molecules |
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Covelent compounds are usually used as |
electrical insulators and circuit breakers |
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Why covalent compounds have low MP and BP |
only a small amount of energy is needed to break the van der waals forces of attraction between molecules hence they have low MP and BP. The strong covalent bonds within the molecules are not broken during M and B . |
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Giant molecular structure ( macromolecules )
Eg to take note |
Graphite diamond silica Polythene Silicon dioxide |
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Properties of giant molecuar structure
- covalent bonds - mp and bp - soft or hard |
- The have strong covalent bonds - Have high melting and boiling points - are hard and used abrasives |
