During an experiment, iron powder and sulfur powder were heated together to form a black mass. it was observed that a magnet, when brought near the black mass, did not attract the black mass. which of the following correctly justifies the observation?
a. the black mass is a mixture and no longer retains the properties of iron.
b. the black mass is a mixture and retains the properties of iron.
c. the black mass is a pure substance and no longer retains the properties of iron.
d. the black mass is a pure substance and retains the properties of iron.

Air pressure is measured in pascals. for a professional american football game, the ball should be inflated to about 90,000 pascals. scientists studied the effects of air temperature on the pressure inside american footballs by taking these steps: 1. prepare 100 footballs. 2. measure each football's air pressure. 3. divide footballs into 10 groups. 4. place the groups in different lockers cooled to different air temperatures. 5. after 12 hours, remove the footballs from lockers. 6. measure each football's pressure again. 7. compare the new pressures to the starting pressures. what two terms best describe the variable "air pressure inside the football" in this experiment? independent, qualitative independent, quantitative dependent, qualitative dependent, quantitative

Describe the properties of sodium, chlorine, and sodium chloride

Why must humans find substitutes for many minerals found on earth? (a) form at an extremely slow rate (b) controlled by other countries (c) too deep in the earth to collect