Bonding, Structure and The Properties Of Matter

• The three states of matter are solid, liquid and gas.

  Melting and freezing between solid and liquid take place at the melting point.

  Boiling and condensing between liquid and gas take place at the boiling point

  The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance
• In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions.
• Gas particles are widely spaced and in constant quick motion. Collisions are frequent and elastic. Weak forces between particles.

  Liquids particles are closely spaced but still in constant motion, and therefore are constantly colliding. Forces between particles less than in solid.

  Solid particles can only vibrate in a fixed posi
• Ionic bonding

  Ionic bonding occurs in compounds formed from metals combined with non-metals.

  When a metal atom reacts with a non-metal atom electrons in the outer shell of the metal atom are transferred.
• Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions.
• The ionic bond is the force of attraction between the oppositely charged ions
• Giant Ionic Structure

  An ionic compound is a giant structure of ions. Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
• Properties of Ionic Substances

  These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong electrostatic forces of attraction between oppositely charged ions .

  When in solid form ionic compounds do not conduct electricity because the ions are fixed in place

  When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
• Covalent bonds are formed between non-metals and non-metals, they share a pair of electrons
• Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.
• These substances do not conduct electricity because the molecules do not have an overall electric charge.
• These substances have only weak forces between the molecules (intermolecular forces). It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils. These require little energy to overcome
• Effect of size of molecule on intermolecular force Intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
• Polymers have very large molecules. The atoms in the polymer molecules are linked to other atoms by strong covalent bonds. The intermolecular forces between polymer molecules are relatively strong and so these substances are solids at room temperature.
• Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances.Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
• In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.
• In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings and so graphite has a high melting point.

  The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.

  In graphite, one electron from each carbon atom is delocalised. These delocalised electrons allow graphite to conduct thermal energy and electricity through the structure.

  Graphite is similar to metals in that it has delocalised electrons.
• Fullerenes are molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. The first fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.

  Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.
• Metals consist of giant structures of atoms arranged in a regular pattern. The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds.
• In pure metals, the atoms are all the same size. The layers of atoms are able to slide over each other. This means metals can be bent and shaped.

  Most metals in everyday use are alloys .

  Pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with other metals to make alloys.

  The different sizes of atoms in an alloy distort the layers in the structure, making it more difficult for them to slide over each other, so alloys are harder than pure metals
• This corresponds to a structure of positive ions with delocalised electrons between the ions holding them together by strong electrostatic attractions In metallic bonding
• Properties of metals

  Strong metallic bonding means that most metals have high melting and boiling points, because lots of energy is needed to break the strong metallic bonds between the positive ions and delocalised electrons.

  Metals are good conductors of electricity because the delocalised electrons in the metal carry electrical charge through the metal. Metals are good conductors of thermal energy because thermal energy is transferred by the delocalised electrons through the structure
• Sun Creams

  Nanoparticles are being used in sun creams. Some of the benefits of nanoparticles in sun creams include better skin coverage and more effective protection from the sun's ultraviolet rays. Disadvantages include potential cell damage in the body and harmful effects on the environment.
• Uses of Nanoparticles

  Nanoparticles have many applications in medicine for controlled drug delivery and in synthetic skin; in electronics; in cosmetics and sun creams; in the development of new catalysts for fuel cells materials; in deodorants and in fabrics to prevent the growth of bacteria. New applications for nanoparticulate materials are an important area of research.
• Bond Types