Many drain cleaners are a mixture of sodium hydroxide and aluminum filings. When these two substances mix in water , they react to produce enough heat to melt the fat in a clogged drain. The bubbles produced are hydrogen gas. The complete reaction occurs in two steps: step 1:Al(s)+NaOH(aq) —> Al(OH)3(s)+Na(aq)
step 2: Na+(aq)+H2O —> Na2O(s)+H2(g)
a) Classify step 1 of the reaction as: addition, displacement, or decomposition.
b) Is this an endothermic or an exothermic reaction?
c) Balance each equation for each step of the reaction.

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.