Composition of Air and Gases

• Air surrounds the Earth, forming the atmosphere.

Compositions of Air

• Air is a mixture of gases which include insects, birds, microorganisms, pollutants, pollen, dust, clouds, water, and satellites.
• Air consists mainly of nitrogen (78%) and oxygen (21%).
• Small quantities of water vapor, carbon dioxide, hydrogen, helium, and argon are also present.
• The amount of gases in air is variable as arid regions have less moisture content than wetlands.
• Nitrogen makes up 78% of the volume in air and is used to fill food packages.
• Oxygen makes up 21% of the volume in air and is essential for keeping living things alive.
• Carbon dioxide makes up about 0.04% of the volume in air and is used to make soft drinks and fire extinguishers.
• Inhaled air contains 78% nitrogen, 21% oxygen, >1% "other" gases, >1% argon, and 0.04% carbon dioxide.
• Exhaled air contains 78% nitrogen, 16.4% oxygen, >1% "other" gases, >1% argon, and 4.4% carbon dioxide.

Testing for Gases

• The Glowing Splint Test is used to test for oxygen.
  • A glowing splint will relight in the presence of oxygen but will be extinguished in other gases.
• The Burning Splint Test is used to test for hydrogen.
  • Hydrogen is an explosive and flammable gas that will ignite the splint with a squeaky "pop" sound.
• The Limewater Test is used to test for carbon dioxide.
  • Carbon dioxide turns limewater (a solution of calcium hydroxide) milky.
• Dry Cobalt Chloride Paper is used to test for water vapor.
  • Dry cobalt chloride paper changes color from blue to purple/pink when dipped in water.

Characteristics of Air

• Air is a clear, colorless gas one cannot see, smell, or taste.
• Air fills up space and has weight.
• Air can move, creating wind.

Heat and Air Movement

• Wind is the movement of air near Earth's surface.
• The Sun warms certain areas more than others, leading to the creation of wind.
• Warm air rises, and cooler air flows in to replace it.
• Onshore wind occurs when wind blows from the sea to the land.
  • The sun heats the land more than the sea during the day, and cooler air from the sea moves in to fill the space originally occupied by hot air.
• Offshore wind occurs when wind blows from the land to the sea.
  • At night, the sea loses heat faster than the land, and cooler air from the land moves in to fill the space originally occupied by warmer air at the sea.

Corrosion and Rusting

• Corrosion refers to the deterioration of materials.
• Rusting is a type of corrosion that happens on iron.
• Rusting refers to the formation of rust on the surface of iron objects.
• Rust is red-brown, flaky, and solid.
• Iron reacts with oxygen and moisture to form iron oxide (rust).
• Corrosion weakens the metal, which leads to serious problems.
  • Rust weakens support structures.
  • Rust reduces the lifespan of objects.
  • Rust acts as an insulator, hindering the electrical conductivity of metals.
  • Rust encourages Tetanus Bacteria to grow.
  • Rust affects the magnetic properties of metals.
• Rusting is sped up with the availability of water in the environment and acidity in the environment.
• Higher oxygen level, high temperatures, and salt accelerates rusting.
• Rust can be prevented by:
  • Painting to keep air away and prevent moisture.
  • Applying oil or grease to moving parts of a machine.
  • Coating iron or steel with a thin layer of Zinc (Galvanizing).
  • Bonding a thin layer of metal to the surface of a metal by electrolysis (Electroplating).

Combustion Essentials

• Combustion is another word for burning.
• Combustion starts when a substance reaches its ignition point (certain temperature) by touching a spark, being heated, or by having strong light on it.
• The products of combustion are carbon dioxide, water and energy (given out as heat and light).
• The fire triangle shows the three essential elements required to start or sustain a fire which are oxygen, fuel and heat.
• A fire will continue as long as all three elements are presented, and removing any one of the elements will extinguish the fire.
  • Oxygen supports the chemical reaction in combustion.
  • Heat raises the material to its ignition temperature.
  • Fuel is any material that can combust.
• Fire fighting equipment:
  • Fire extinguisher
  • Fire blanket
  • Fire hose

Fire Safety Rules

• Never play with fire or matches.
• Turn off all candles, irons, heaters, stoves and paraffin stoves before you go to bed.
• Stay away from hot water.
• Never play too close to a lit candle, a fire or a gas heater.
• Stop, drop, and roll if clothing catches on fire.
• Never hide during a fire.
• Stay low on the floor during a fire.
• Get out of a burning building quickly and stay out.
• Have a family meeting place that is away from the fire.
• Call for help in the event of an emergency.
• Cool a burn with cold water for 20 minutes, do not apply other chemicals on the burn, and call for help straight away.