CHEMISTRY 9E Flashcards
What are ceramics?
They are a range of hard, durable, non- metallic materials that are generally unaffected by heat
How are ceramics formed?
Often formed by heating and then cooling.
Examples of ceramics?
Ceramics include traditional bricks, china and glass as well as more modern materials used to make artificial bones and protective coverings for space crafts
Physical properties of ceramics?
- hard, stiff, strong when compressed, and brittle
- high melting points and heat resistant
- good insulators of heat and electricity
- very unreactive
What happens when clay is heated?
Chemical reactions occur and new compounds, such as China and porcelain, are formed
What happens during cooling?
During cooling, crystals form and bind together in the ceramic.
What does the size of the crystals depend on?
The size of the crystals depends on the speed of cooling. Slower cooling produces larger crystals.
Why does slower cooling produce larger crystals?
Because the atoms have more time to form a grid-like lattice structure. This is similar to the formation of large crystals in granite when magma cools slowly
What happens in a lattice structure?
There are a large number of atoms, in a fixed regular lattern, all joined to each other by strong bonds.
Why are ceramics stiff?
One reason is because there are so many atoms bonded to each other, with strong bonds, in a rigid structure. This high strength of the bonds is the reason why ceramics have such high melting points.
Why is glass slightly different than other ceramics?
It is different because its atoms do not form a regular pattern, although the atoms are still held together by many strong bonds.
What is porcelain used for?
For cable supports on electricity pylons as it does not conduct electricity
What is China used for?
For tableware, as it is strong and a heat insulator
Natural Polymers?
- Rubber
- Wool
- DNA
- Proteins
- Starch
Synthetic Polymers?
Synthetic rubber Poly vinyl Poly ethene Poly propene Nylon
Rubber properties?
Soft and sticky when hot
Hard and brittle when cold
Why are polymers elastic?
They are elastic because the long coiled molecules go back to their original shape when streched
How are polymers formed?
They are formed by joining together many small molecules called monomers
What happens if crosslinks are formed between chains?
It makes the polymer harder and less easy to melt
What does Vulcanisation do?
It uses sulfur to form cross-links in rubber molecules
What is poly(ethene) used for?
It is used for plastic bags and buckets as it is strong, flexible and durable
Characteristics of Polymers?
They are generally strong, flexible, non conductors of heat and electricity, durable and unreactive
What is poly(vinyl chloride) used for?
It is used for covering electrical cables as it is flexible, strong and a non conductor of electricity
What are most synthetic polymers made of?
Raw materials obtained from crude oil
What is a composite material?
Composite materials are combinations of two or more materials, with some of the properties of each
How are many composite materials made by?
They are made by mixing fibres into a liquid resin which then sets hard. Different types of fibres and resins produce different composite materials with different properties and uses
What is concrete used for?
Concrete is a composite material that has been used for thousands of years, it is used for large structures because it is strong and durable.
What is concrete made of?
It is made from a mixture of cement, sand, aggregate (crushed rocks) and water
Why are composite materials useful?
They are useful because they combine the properties of all the materials they are made from
What happens in safety glasses?
Layers of glass are combined with clear polymer
What is an exothermic reaction?
The ones that transfer energy to the surroundings so the temperature of the surroundings rises
What is an endothermic reaction?
A reaction that transfers energy from the surroundings so the temperature of the surroundings falls
Structure of a composite material?
Many composite materials cantain fibres embedded in a matrix or resin
Thermal decomposition reaction of cement?
CaCo3. ->. CaO. +. CO2
Calcium carbonate. calcium oxide+ carbon dioxide
What is the word equation for combustion of carbon?
Oxygen + Carbon -> carbon dioxide + water
What is the word equation for combustion of sulfur?
Oxygen + Sulfur -> Sulfur Dioxide + Water
Word equation for combustion of nitrogen?
Oxygen + Nitrogen -> Nitrogen Oxide + Water
Incomplete combustion of Carbon?
Oxygen + Carbon -> Carbon Monoxide + Water
Burning fissil fuels provides the energy needed to make materials but is also linked to?
- Acid Rain from production of sulfur dioxide
- Increase in carbon dioxide levels and the greenhouse effect
- soot dirtying buildings and damaging health
How does acid rain work?
Sulfur dioxide and nitrogen oxides, are acidic gases that dissolve in clouds and fall as acid rain
What causes acid rain?
- Sulfur dioxide, caused by sulfur impurities in fuels, can form acid rain
- Nitrogen oxides, caused by combustion temperatures, can also form acid rain.
Problems with making and using materials?
- Toxic substances released in waste get into food chains
- As large animals eat lots of smaller animals, toxin levels increase (biogmanification) and can reach harmful levels in humans.
- Non-biodegradable polymer waste causes pollution problems and dangers to animals for years
Solutions to making and using materials?
- Removal of sulfur from fuels
- Reduction in the use of fossil fuels and use of more renewable energy sources
- Control of hazardous waste from factories
- Use of biodegradable polymers, which break down in the soil, so they disappear quicker
Key Features of recycling materials to use again?
- Reduces our use of landfill sites
- Reduces the need to burn fossil fuels
- Reduces pollution from manufacturing process
- Saves our resources of raw materials, e.g. metal ores for metals and wood for paper
Examples of materials that can be recycled?
Metals - by separating and melting
Glass - by separating colours and melting
Polymers - by using recycle labels
Paper- by removing ink and adding water to make a pulp
Concrete- by crushing and grading
What is an example of and Exothermic Reaction?
Combustion reactions, because it transfers energy into the surroundings and increase the temperatures
Example of an Endothermic reaction?
Decomposition reactions because they transfer energy from the surroundings and therefore decrease the temperature
