Acetylene is the only fuel gas suitable for gas welding because of its favourable flame characteristics of both high temperature and high propagation rates. Other fuel gases, such as propane, propylene or natural gas, produce insufficient heat input for welding but are used for cutting, torch brazing and soldering.
The three broad classes of elements are:
Metals
Metalloids
Nonmetals
The formula for hydrogen-hydrogen is H-H
Answer:
aphelion
Explanation:
A planet moves with constantly changing speed as it moves about its orbit. The fastest a planet moves is at perihelion (closest) and the slowest is at aphelion (farthest).
