That create stars, scientists understand more and more about how the universe came into existence. The ne little green men up in space, think about all the great astronomers who have studied the night sky in search
Question 1
Using the information in the passage, rank the types of galaxies by their ability to form new stars, from most to
least activity
.
Elliptical, spiral, irregular
Irregular, elliptical, spiral
Spiral, irregular, elliptical
Irregular, spiral, elliptical
Son

you need to stop taking that class

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.