D. It gives the same results when experiments are repeated
The wood turns into ash and smoke so mass is nor destroyed or created.
A) all mechanical waves need a medium to travel through.
This is true because mechanical waves move in a wave like manner at the atomic level. This is why an table vibrates when you put a speaker on top of it .
The density of helium is 10 ^-3g.cm^-3
Helium
Remember: electron filling of atomic shell ...
The element which have electron in the lowest quantum shell will have the smallest atomic radius\
He:1s1 (Helium)
H:1s2 (hydrogen)
