Chemistry. Chemicals of the natural environment C5

COVALENT BONDING

• Pure molecular compunds do not conduct, electricity because their molecules are not charged.
• Atoms in molecular substances are joined by covalent bonds.
• Covalent bonding... from electrostatic attraction between the nuclei of the atoms and the electrons shared between them.
• Low melting and boiling point

IONIC BONDING

• Ions held together by attraction between opposite charges
• Giant 3 dimensional structure
• Very strong
• High melting and boiling points
• Conduct when dissolved or molten

Biosphere

• Carbohydrates, proteins and DNA are molecules
• Living things mainly made up from the elements, C, H, N and O.
• Chemicals can move between the spheres as part of cycles.
• Elements make up molecules vital for living... Carbohydrates, proteins, fats and DNA.

Lithosphere

• Earths outer layer is made from mainly silicon, oxygen and aluminium.
• Silicon dioxide is hard, has a high melting point, is insoluble in water and doesn't conduct electricity.
• Silicon dioxide GIANT structure.
• Atoms held together by strong covalent bonding.
• Some minerals make valuable gem stones because of their rarity and hardness.

• Ores are rocks that contain minerals from which metals can be extracted.
• When a metal loses oxygen it is reduced.
• When carbon gains oxygen it is oxidised.
• Electrolysis - Decomposition of electrolytes with electricity
• Electrolytes conduct electricity but decompose.
• Electrolytes include molten ionic compounds
• Metals form at the negative elctrode (cathode)
• Non-metals form at the positice electrode (anode)
• The properaties of metals affect how they're used... Strength, malleability , melting point and conductivity.
• CYCLE. Mining -> Landfill -> Energy costs