26 - Bulk & Surface Properties of Matter (Including Nanoparticles) Flashcards
What are the properties of Glass?
- Transparent
- High mp
- Brittle
- Poor conductors of heat & electricity
How is glass made?
Glass is made by melting sand with other substances (especially metal oxides), then allowing the molten liquid to cool and solidify
What are the properties of Clay?
- Opaque
- High mp
- Brittle
- Poor conductors of heat & electricity
How are clay ceramics made?
They are made by heating clay to high temperatures, which causes crystals to form and join together
They are often coated with a glaze
What is the purpose of the glaze in clay ceramics?
Forms a hard, smooth, opaque and waterproof layer
Give some examples of clay ceramics
- Brick
- China
- Porcelain
What are the properties of Metals?
- Shiny
- High mp
- Malleable
- Good conductors of heat & electricity
What are the properties of Polymers?
- Poor conductors of heat & electricity
- Rest of the properties depends on the particular polymer
What is a composite material?
Material made from two or more different materials with contrasting properties
What are the components that most composite materials have?
- The reinforcement
- The matrix, which binds the reinforcement together
What is the matrix?
The substance that binds the reinforcement together in a composite material
What is reinforcement?
Fibres or other material that make up the bulk of a composite material
What is Tensile strength?
The tension a material can withstand without breaking
What are some examples of composite materials?
- Reinforced concrete
- Fibreglass
- Chipboard
- Carbon fibre reinforced polymer
What is the matrix in the Reinforced concrete composed of?
Concrete
What is the reinforcement in the Reinforced concrete composed of?
Steel
How does reinforcing concrete with steel improve concrete’s physical properties?
- The compressive strength of concrete is higher than its tensile strength.
- The tensile strength of steel is higher than its compressive strength.
–> The combination of these 2 materials makes the reinforced concrete strong in tension and in compression.
Why is important that reinforced concrete has high compressive and tensile strength?
This allows reinforced concrete to be strong and slightly flexible, which is important when constructing large buildings and structures
What is the matrix in the Fibreglass composed of?
Polymer resin
What is the reinforcement in the Fibreglass composed of?
Glass fibres
What is the matrix in the Carbon fibre reinforced polymer composed of?
Polymer resin
What is the matrix in the Chipboard composed of?
Resin glue
What is the reinforcement in the Carbon fibre reinforced polymer composed of?
Carbon fibres
What are some properties of Fibreglass and carbon fibre?
- Low density (lightweight)
- Strong in tension
What is the key property of the polymer resin used in Fibreglass & Carbon fibre?
It is not strong but it is stiff
What is the key property of the fibres used in Fibreglass & Carbon fibre?
It is strong in tension (so it’s not easily stretched) but they are flexible
What is the reinforcement in the Chipboard composed of?
Wood chips
What are the properties of a Chipboard?
Very Strong
Why are chipboards very strong?
Chipboard contains randomly arranged wood chips bonded together by a glue, so it is strong in all directions
What is the reinforcement in wood composed of?
Cellulose fibres
What is the matrix in wood composed of?
Lignin
Why is wood stronger in one direction than the other?
The cellulose fibres of wood are aligned alongside each other
What are nanoparticles?
Tiny particles which are between 1 and 100 nanometres (nm) in size
What is a nanoparticulate?
Useful substances containing nanoparticles
What does the uses of nanoparticulates depend on?
- Small size of the nanoparticles
- Large surface area to volume ratios
How big are nanoparticles in comparison with atoms?
They typically consist of just a few hundred atoms
What are some uses of nanoparticulate materials?
- Sunscreens
- Catalysts
- Stain-resistant clothes
What is titanium dioxide in bulk?
A white solid
How does the nanoparticulate titanium dioxide look like?
Its transparent because the particles are very small
What does titanium dioxide do?
Absorbs harmful UV radiation present in sunlight
What is titanium dioxide found in?
Sunscreens (especially the sunscreens which are almost invisble)
How are nanoparticulate materials useful as catalysts?
The very large surface area : volume ratios allow them to act efficiently as catalysts
They:
* Catalyse reactions more efficiently
* Catalyse different reactions
* Produce different products
How do stain-resistant clothes treated with nanoparticles stay clean?
The nanoparticles catalyse the breakdown of dirt
What are some risks of nanoparticulate materials?
Small size - makes it possible to breathe them in or pass into cells
Why might it be dangerous that nanoparticles can pass into cells?
They might catalyse reactions that are harmful
Toxic substances could bind to them because of their large surface area to volume ratios, harming health if the nanoparticles do get into the body.
Why are the risks of nanoparticles difficult to determine?
Modern nanoparticulate materials have not been in use for long
