If 0.025 gram of pb(no3)2 is dissolved in 100. grams of h2o, what is the concentration of the resulting solution, in parts per million?
(1) 2.5 × 10–4 ppm (3) 250 ppm
(2) 2.5 ppm (4) 4.0 × 103 ppm

Freezing and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.

An alloy contains 66 g of pure zinc. what is the percentage of zinc in the alloy? express your answer to two significant figures and include the appropriate units.

What type of electromagnetic waves does the human eye see as the colors red blue or green a visible light waves b radio waves c infrared waves d microwaves