Why were birds and butterflies placed into different groups within the biological classification system?

Amixture that has two or more substances that are spread out evenly is called a. compound b. heterogeneous c. substance d. homogeneous

How many moles of lead are in 1.50 x 10^12 atoms of lead? could you explain the answer as well and not just give it to me i am refreshing for finals and i need to know how to do it

Convert the temperature of dry ice, –77 ∞c, into degrees fahrenheit and kelvin.