Answer:
I think #3 might be the answer .
Because in #1 atomic mass tells mass .
#4 Atomic number doesnot only tell about the electrons atom has
Answer: You can increase the weight, then test the speed, and make the weight normal and test the speed, and mark which one travels faster.
Explanation: This would test your hypothesis by comparing the speeds of the cars when more mass is added. Calculating the difference of the speed with more mass, and the speed with normal mass would give you your answer. A positive number would prove your hypothesis and a negative number would disprove it.
The ideal gas law (PV = nRT) relates the macroscopic properties of ideal gases. An ideal gas is a gas in which the particles (a) do not attract or repel one another and (b) take up no space (have no volume).
Answer:
Explanation: A yellow precipitate o lead iodide is formed. see equation of reaction below: 
→ 
Th PbI2 is the insoluble yellow precipitate
C. Formation of a new substance
