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The part of the atmosphere closest to the Earth; the part of the atmosphere that organisms on Earth use for respiration
Air
The metric temperature scale: Water boils at 100 degrees Celsius, and it freezes at 0 degrees Celsius
Celsius
A state of matter without any defined volume or shape in which atoms or molecules move about freely
Gas
The layers of gases that surround the planet
Atmosphere
The force per unit of area exerted on an object
Pressure
Small, icy balls that fall from the sky
Hail
The region around the North Pole defines by the Arctic Circle, or pertaining to physical or biological features related to that region
Arctic
Water that is released from clouds in the sky; includes rain, snow, hail, and freezing rain
Precipitation
In weather, the boundary between two masses of air with different properties
Front
The third planet from the sun; the planet on which we live
Earth
A collection of water droplets or ice crystals in the atmosphere
Cloud
The properties of the atmosphere at a given time and location, including temperature, air movement and precipitation
Weather
An object's mass divided by its volume; a measure of how many particles are packed together in a certain amount of space
Density
An element that makes up most of the air near earth's surface, this element is a gas at room temperature
Nitrogen
A measure of how much water is in something
Moisture
Tropical
The gaseous form of water; produced when water evaporates
Water Vapor
Liquid water that falls from the sky
Rain
A compound made of hydrogen and oxygen
Water
A measure of the average kinetic energy of the atoms in a system, used to express thermal energy in degrees
Temperature