How many moles of hydrogen atoms are present in 25.0 g of water?

M(H₂O)=25.0 g
M(H₂O)=18.02 g/mol

n(H₂O)=m(H₂O)/M(H₂O)

n(H)=2n(H₂O)=2m(H₂O)/M(H₂O)

n(H)=2*25.0/18.02=2.775 mol

Matter- occupies space and possesses rest massno matter is the opposite

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.