Chapter One Flashcards
Materials in our world
What are Materials?
- Substances used to make objects
- Can be a mixture of substances or pure elements/compounds
Examples of materials
- Wood
- Nylon
- Paper
Substances not considered materials
Chemicals such as hydrochloric acid, chlorophyl and carbon dioxide
Definition: Element
Pure substances that are made up of just one type of atom
Example of an element
- Carbon
- Gold
- Silver
What are Compounds?
- Pure substances made up of more than one type of atom
- They consist of more than one type of element in fixed proportions
Examples of compounds
- SiO2 (silica)
- H2O (water)
- C6 H12 O6 (glucose)
Chemical/physical properties that influence a materials use
- Colour
- Hardness
- Melting point
- Boiling point
- Conduction of electricity
- Conduction of heat
- Ability to react with other chemicals
Can properties of elements/compounds be altered
Thay cannot be as they are pure substances
How are the properties of elements/compounds determined
Determined by the arrangement of their atoms molecules and are distinct and measurable for given arrangement of atoms and molecules
Can properties of mixtures change
Can be changed depending on the concentration of each element in the mixture which makes them very useful materials
What is Mixture?
A physical combination of two or more substances that do not change their chemical makeup or form or break bonds with each other
What are Metals properties?
- High tensile strength
- Ductility
- Malleability
- Shiny luster
- High melting point
- Thermal conductivity
- Electrical conductivity
Categories of materials
- Metals
- Polymers
- Ceramics
What is Metals?
- Valuable materials due to their properties
- 80% of all known elements
- Found in elemental metallic forms and as compounds known as minerals
How can you improve a metals weak point
Use an alloy of the metal
What are Alloy?
A mixture of a metal with other metals or small amounts of non-metals
What are Polymers?
- A material with a molecular structure that is composed of many repeating smaller units bonded together
- Includes plastics, nylon and rubbers
- Natural and synthetic polymers
Properties of Polymers
- Less dense
- Corrosion resistant
- Electrical resistance
- Polymers of biological nature offer good compatibility with human skin
What are Ceramics?
- An inorganic, non-metallic solid
- Natural and synthetic ceramics
- The degree of order within ceramic materials can range from highly ordered to highly irregular
Example of natural polymers
- Wool
- Paper
- Silk
Example of synthetic polymers
Polystyrene
Example of natural ceramics
Kaolinite (used to make porcelain)
Example of synthetic ceramics
Silicon carbide (used as an abrasive)
What is a structure that is highly ordered called?
Crystalline
Highly irregular
Amorphous
What are Composite materials?
- A combination of two or more distinct materials with distinctly different physical or chemical properties
- Has properties that are unobtainable by using an individual material
What are Nanotechnology?
The science that investigates the design, properties and application of materials on the nanoscale
What is a Nanoscale?
- Structures between 1 and 100 nanometers across
- 1 nanometre is a billionth of a metre
What are Nanomaterials?
Substances both natural and synthetic that are composed of single units that exist on the nanoscale
Example of nanomaterials
Fullerenes (family of carbon molecules)
Fullerenes
Three-dimensional structures formed by a network of carbon atoms
Which fullerene promises the most opportunities
The cylindrical tube known as the carbon nanotube
Carbon nanotubes
Formed from a layer of two-dimensional carbon atoms arranged in hexagons known as graphene
Carbon nanotubes properties
- Finds a use as a reinforcement in composite materials
- Interesting electrical properties
- Exceptional strength
- Stiff
- The base of all superconductor research
The two ways materials on the nanoscale can be fabricated
- Bottom-up fabrication
- Top-down fabrication
Top-down fabrication
Starts with a material of a much larger scale than desired which is then selectively removed or the size of the material is gradually reduced through grinding until the required shape and size is formed
Examples of top-down fabrication
- Computer chips
- Sunscreen
Advantages of top-down fabrication
Large quantities of material can be produced cheaply and the product demonstrates good levels of uniformity
Disadvantages of top-down fabrication
Limited to relatively simple structures and by the scale of the tools used to remove the material from the starting medium
Bottom-up fabrication
Physically growing or building the required material atom by atom or molecule by molecule until the required shape and size is formed
Advantages of bottom-up fabrication
Can be used for far more complicated structures due to the ability of being able to manipulate atoms/molecules at the nanoscale
Disadvantages of bottom-up fabrication
They do not scale up to commercial levels efficiently and thus are currently only economical for research and niche applications
Nanoparticles
- A specific type of nanomaterial
- Usually spherical with diameters of 1-100nm
- In this size the properties of materials begin to change from those normally observed for bulk material due to greater contribution of Quantum effects
- Potential in medicine, physics, optics and electronics
Separation techniques using either physical or chemical properties
- Particle size
- pH
- Density
- Solubility
- Electric charge
Separation through particle size
- Sieving
- Filtration (vacuum and gravitational)
Sieving
- Passing a mixture through a mesh, particles smaller than the holes in the mesh will pash through leaving larger ones behind
- Separate a mixture of solids with different particle size
Filtration
- Separate solid particles from liquid or gas
- Filter paper seperates liquid from solids
Gravitational filtration
- Using the weight of the mixture to push the mixture through the filter paper
- Purified liquid = filtrate
- Solid = residue
Vacuum filtration
- Faster than gravitational and helps dry the residue faster
- Rubber seal and side arm on the conical flask
Separation by density
- Sedimentation and decantation
- Separation funnels
- Centrifugation
Sedimentation and decantation
- Sedimentation = settling (form of gravitational separation)
- The liquid can then be separated from the sediment very carefully, pouring the liquid into another container (decantation)
- Cheap method, large volumes
Seperation funnels
- If two different liquids have different densities and are immiscible they can be separated by a separation funnel
- Liquid- liquid extraction
Centrifugation
Spinning a mixture rapidly- speeds up the sedimentation process and extracts finer particles that may not settle naturally
Seperation by boling point
- Evaporation
- Distillation
- Fractional distillation
Evaporation
The liquid solvent is boiled off to reveal the solid solute
Distillation
Similar to evaporation but uses an apparatus to recover the evaporated liquid
Fractional distillation
- Separate miscible liquids when their boiling points are slightly different
- Same as distillation flask but with an extra column which allows for increased contact between rising vapour and falling condensate
Seperation by electric charge
Chromatography
Chromatography
Separates liquids based on their differing affinity for various materials present in the chromatography apparatus
