Weather

2. the ratio of the mass of an object compared to its volume
4. the gaseous envelope (air) surrounding the Earth to a height of 1,000 km (621 miles): it is 21% oxygen, 78% nitrogen, and 1% other gases, and rotates with the Earth because of gravity
5. the height of an object from the surface of the Earth or the distance above sea level
9. outermost layer of the atmosphere
10. Gas any gas in the atmosphere that traps heat and helps keep the Earth warm
11. the transfer of energy through direct contact
12. an instrument that measures air pressure and shows when the weather is changing

1. the movement in a gas or liquid in which the warmer parts move up and the cooler parts move down
3. middle layer of the atmosphere
5. Pressure the measure of the force with which air molecules push on a surface
6. the measure of how fast atoms and molecules of a substance are moving (the warmer a molecule is the faster it moves and the more space it needs)
7. the first layer of the atmosphere
8. the fourth layer of the atmosphere
13. the process by which energy moves in the form of waves or particles