- Created by: maddieecarr
- Created on: 07-12-19 10:51
C3.1: States of Matter
- the three states of matter are solid, liquid and gas.
- the particles in a solid are packed closely together and vibrate around fixed positions
- the particles in a liquid are also close together but can slide over each other in random motion.
- the particles in a gas have a lot of space between them and zoom around randomly
- in melting and boiling, energy is transferred from the surroundings to the substance
- in freezing and condensing, energy is transferred from the substance to the surroundings.
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C3.2: Atoms into Ions
- elements react together to form compounds by gaining, losing or sharing electrons
- the elements in group 1 react with the elements in group 7
- as they reach, each atom of group 1 can lose one electron to gain stable electronic structure of a noble gas.
- this electron can be given to a group 7 element, which also achieves the stable electronic structure of a noble gas.
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C3.3: Ionic Bonding
- ionic compounds are held together by strong forces of attraction between their oppositely charged ions
- this is called ionic bonding
- apart from the elements in groups 1 and 7, other elements can form ionic compounds, such as those from groups 2 and 6, forming 2+ and 2- ions respectively
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C3.4: Giant Ionic Structures
- a lot of energy is needed to break the many strong ionic bonds, which operate in all directions and form a giant ionic lattice
- ionic compounds have high melting points and are solid at room temperature
- ionic compounds will conduct electricity when molten or dissolved in water
- this is because their ions can move around and carry charge through the liquid.
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C3.5: Covalent Bonding
- covalent bonds are formed when atoms of non-metals share pairs of electrons with each other
- each shared pair of electrons is a covalent bond
- many substances containing covalent bonds consist of simple molecules but some have giant covalent structures
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C3.6: Structure of Simple Molecules
- substances made up of simple molecules have low melting and boiling points
- the intermolecular forces are weak and explain why they have such low boiling and melting points
- simple molecules have no overall charge so cannot carry electrical charge
- substances made of simple molecules do not conduct electricity.
- models are used to help understand bonding but each model has its limitations
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C3.7: Giant Covalent Structures
- some covalently bonded substances have giant structures
- these have very high melting and boiling points
- graphite contains giant layers of covalently bonded carbon atoms
- there are no covalent bonds between the layers which means they can slide over each other.
- the carbon atoms in diamod have a rigid giant covalent structure making it a very hard substance
- graphite can conduct electricity and thermal energy because of the delocalised electrons that can move along the layers.
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C3.8: Fullerenes and Graphene
- carbon also exists as fullerenes, which can form large cage-like structures and tubes, made of hexagonal rings of carbon atoms
- the fullerenes are used as transport mechanisms for drugs to specific body sites, catalysts and reinforcement for composite materials
- graphene is a single layer of graphite and is one atom thick
- it has high electrical conductivity and will help create developments in the electronics industry
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C3.9: Bonding in Metals
- the atoms in metals are closely packed together and arranged in regular layers
- metallic bonding is positively charged metal ions, held together by electrons from the outermost shell of each metal atom
- the delocalised electrons are free to move throughout the giant metallic lattice.
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C3.10: Giant Metallic Structures
- metals can be bent and shaped because the layers of atoms in a giant metallic structure can slide over each other
- alloys are harder that pure metals because the regular layers in a pure metal are distorted by atoms of different sizes in an alloy
- delocalised electrons in metals enable electricity and thermal energy to be transferred through a metal easily
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