Answer:
False
Explanation:
Molecules of the same substance are made up of the same type of atoms and look exactly alike.
Hence, if I have two molecules of methane having exactly the same atoms of carbon and hydrogen,the both are indistinguishable from each other based on appearance.
Hence all molecules of methane are exactly alike if they are composed of atoms of the same isotope of hydrogen and carbon.
Concave is not a type of mechanical wave because it doesn’t need a medium for propagation.
Answer:
444 L
Explanation:
According to Archimedes the buoyancy force is equal to the weight of the displaced substance. In this case, the displaced substance is Air. So to calculate the lifting power of Helium, start with the weight of air in volume
Since the Helium itself has weight, we need to use the difference in density between air and helium.
We know that the density of air is 1.2 
Density of Helium is 0.1787 
To lift a object of 1 pound which is equal to 0.453 kg we need

helium There is 1000 liters in a 
So the required volume of helium= 0.444×1000=444 L
A scientist may repeat an experiment to make sure that results are reliable. An example would be if the test had a large variance in data gathered and no conclusions could be drawn.