Two balloons are hanging from a string. A students comes along and rubs the balloons on their hair. When they let go the balloons are pushing away
from each other. What is the reason the balloons repel?

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?

Citric acid has a ph between 1 and 3.  it is considered to be aa. weak acidb. weak basec. strong based. strong acid

Why does 4.03/0.0000035 = 1.2 x 106, instead of a different number of significant figures?