### oxide:

Zirconia
* can exhibit three different crystal structures depending on temperature.
* component in some abrasives , such as grinding wheels and sandpaper.
* is chemically unreactive
  - stable in oxidizing and mildly reducing atmospheres
  - used to make ceramic knives
  - what confers alkali resistance in glass

Zirconium oxide
* has low thermal conductivity and high melting point.
* is extremely hard, wear resistant, and chemically inert
  - oxide
  - relatively stable on silicon surface and has a high dielectric constant
  - used to make heat resistant crucibles, ceramics and abrasives
* very strong material.

### oxides:

Ore mineral
* Many ore minerals are oxides.
* can be metallic and non-metallic.
* consist of magnetite, ilmenite, hematite, ulvospinel and rutile.

### ozone precursor:

Nitrogen oxide
* Some nitrogen oxide causes acid rain
* Some nitrogen oxide creates acid rain
* appear as yellowish-brown clouds over many city skylines.
* are a by-product of combustion processes, eg aircraft emissions
  - class of compounds made of nitrogen and oxygen in varying percentages
  - key component of smog
* are a major contributor to ozone production and smog
  - ingredient of acid rain
  - precursor to ozone creation
  - acidic
* are also a precursor pollutant that contributes to the formation of acid rain
  - dangerous to plants
  - major components of acid rain
  - an important precursor to both ozone and acid rain
  - another significant contributor to haze over the Grand Canyon
  - by-products of burning fuel in automobiles and heavy industries
  - corrosive to steel when cooled to low temperatures in the presence of water
  - largely a product of high-temperature combustion
  - one of the key components that leads to the formation of ground-level ozone
  - ozone precursors
* are precursors of acid rain and smog
  - to ground level ozone
  - produced in the emissions of vehicle exhausts and from power stations
  - relatively insoluble in water
  - smogformers, which react with volatile organic compounds to form smog
* are the primary component of photo-chemical smog
  - pollutants of concern from natural gas combustion
  - result of high temperature combustion
* big contributor to smog.
* can form in process furnaces
  - ozone, an irritating substance in smog
  - travel hundreds of miles after leaving a smokestack or tailpipe
* cause air pollution
  - the brown haze seen over many cities
* causes smog.
* combine with hydrocarbons to form ozone, one of the region's worst pollutants.
* combined with hydrocarbons in the atmosphere creates ozone, or smog.
* come from burning gasoline, coal, or other fossil fuels
  - more from automobiles than from electric power plants
* comes from the exhaust of cars.
* component in the production of photochemical smog.
* component of ozone
* contribute most of the atmospheric contaminants.
* contribute to both ground-level ozone and acid rain
* exert their effects on the environment both in the form of oxides and as acids.
* form naturally in the atmosphere when lightning strikes a molecule of nitrogen gas.
* have a chemical smell, and can be a lung irritant.
* help form acid rain.
* is an ozone precursor
  - more common, but relatively less harmful
* is the key smog-forming pollutant targeted in the smog plan
  - major component in the formation of low-level ozone, which is hazardous
* key ingredient of ground-level ozone, which primary component of smog.
* landing on paved surfaces also add to the nutrients contained in runoff.
* lead to smog and acid rain, and hydrocarbons produce smog.
* major factor in the creation of ground level ozone
  - formation of smog as well as acid rain
* play a major role in producing smog.
* plays a key role in producing smog.
* primary ingredient of ground-level ozone or smog.