Chemisty

• What are the physical properties of metals?

  - Malleable (They can be shaped)

  - Ductile (They can be pulled into wires)

  - Good conductor of heat

  - Good conductor of electricity

  - High melting points

  - High boiling points

  - High density

  - Lustrous

  - Strong
• How are metals held together?

  Metals are held together in a giant structure by metallic bonding, which is a strong bond.
• What is metallic bonding?


  Metallic bonding is a regular arrangement (lattice) of positive ions in a sea of free electrons, with strong bonds and electrostatic attractions.

  
• How are the positive ions formed in metallic bonding?

  The positive ions form by the loss of an atom's outer shell electron. These electrons behave as a glue that holds the positive ions together.
• How do metals conduct heat?

  When the particle is heated, it gains kinetic energy and vibrates. The vibration is then passed on easily to the next particles. The free electrons can move faster when heated and transfer heat to the colder parts of the metal.
• How do metals conduct electricity?

  There has to be a flow of electrons for an electrical current to flow. The free outershell electrons can pass the current through and conduct electricity.
• How are metals malleable and ductile?

  Its the bonding that cause them to be malleable and ductile. The free electrons allows the positive ions to slide over each other without breaking the metallic bond.
• Why do metals have high melting and boiling points?


  The bond is strong and requires a lot of energy to break, which results in a high melting point and boiling point. The more electrons in the outershell, the higher the melting point.
• How do ions form?

  Atoms want to achieve one thing - a full outershell. To do this, they lose or gain electrons and form ions.

  
• What is ionic bonding?

  Ionic bonding is another way that atoms can be held together. This type of bonding results in a giant ionic structure or lattice.

  
• What does ionic bonding involve?

  - Ionic bonding involves ions.

  - Ionic bonding will always happen between a metal and a non-metal.

  - The positive ions and negative ions form a lattice.
• * What happens when potassium reacts with iodine to produce potassium iodide?*- Potassium atom would react with the iodine atom, causing the potassium atom to lose one electron and the iodine atom to gain one electron (in order to gain full outershells).

  - This will enable them to turn into ions (potassium ion and iodide ion).

  - This will form K+ and I-.

  - They turn into ions as they'll have full outermost shells.
• What is a lattice?

  A lattice is a regular arrangement of particles. Each ion is surrounded by 6 oppositely charged ions.

  
• Why do ionic compounds have high melting points?

  Ionic compounds are held together by strong electrostatic forces which need a lot of energy to break. It needs to be heated to a high temperature to break the bonds.
• Why are ionic compounds soluble in water?

  Water can attract ions away from the lattice, and so dissolve the substance.
• How do ionic compounds conduct electricity?


  Ionic compounds only conduct electricity when molten or dissolved, as the ions have to be free to move and carry an electrical current.
• What is a covalent bond?


  Non-metals bond by covalent bonding. Covalent bonding is where elements bond by sharing electrons to gain a full outermost shell.

  
• Why do simple covalent structures have low melting and bonding points?


  The intermolecular forces between simple covalent structures are very weak, and do not require a lot of energy to break - which causes them to have a low melting and boiling point.
• Why do simple covalent structures not conduct electricity?

  They are electrostatically neutral, and when molten or dissolved, don't include charged particles to conduct electricity.
• What is an intermolecular force?

  An intermolecular force is the force in between simple molecules.

  
• What are giant covalent structures?

  Some covalent substances exist as giant structures that have high melting points. These include:

  - Graphite

  - Diamond

  - Nanotubes

  - Buckminsterfullerene

  - Graphene

  
• What are carbon allotropes?

  Carbon allotropes are different forms of carbon bonding. Carbon can form graphite, diamond, fullerenes, nanotubes and graphene - which are all known as allotropes.
• What are the properties of diamond?


  - Very hard (hardest substance on Earth)

  - Very high melting and boiling points

  - Does not conduct electricity
• What are the uses of diamond?


  - Gemstones

  - Glass cutting and drill bits
• What are the properties of graphite?


  - Soft and slippery

  - Good conductor of electricity

  - High melting point
• What are the uses of graphite?

  - Lubricant

  - Used in pencils

  - Electrodes
• What are carbon nanotubes?

  - They have a very small diameter.

  - Made from single layers from a graphite structure, rolled into tubes.

  - Much smaller than carbon fibres.

  - Can be used in miniature electric circuits and as lubricants.

  
• What are the properties of carbon nanotubes?

  - Strong and have a low density

  - Good conductor of electricity
• What is buckminsterfullerene?

  Buckminsterfullerene is another type of fullerene that is shaped into a football structure.

  
• What are two uses for buckminsterfullerene?

  - Cosmetics

  - Carrying drugs
• What is graphene?

  Graphene is a single layer of carbon atoms that are bonded together in an hexagonal honeycomb lattice.

  
• What are smart materials?

  Smart materials are those that can change their properties reversibly with a change in their surroundings.
• What are thermochromic pigments?

  They change colour with changing temperature.
• What are photochromic pigments?

  They change colour with changing light intensity.
• What are hydrogels?

  They absorb/expel water and swell/shrink (up to 1000 times their volume) due to changes in pH or temperature.
• What are shape memory alloys?

  They regain their original shape when heated.
• What are shape memory polymers?

  They regain their original shape when heated.
• What are uses for thermochromic pigments?

  - Novelty mugs

  - Kettles

  - T-shirts

  - Contact thermometers
• What are the uses for photochromic pigments?

  - Lenses in glasses

  - Car windows
• What are the uses for hydrogels?

  - Contact lenses

  - Artificial snow

  - Baby nappies

  - Wound dressings

  - Pipe shut-offs