text: chemistry homework ? you dont necessarily have to answer all of these questions, i rather know how to solve it than get the answers..  help please :[  1 )how many significant figures are there in the measurement 20,500 and0.0120g ?  2) a cube measures 3.00 cm on an edge and has a mass of 16.23g.  the correct density is ?  3)express the sum of 5.0 cm an 11.28 cm to correct number of significant figures.  4) helium boils at a temperature of 4k what is this temprature in celcius?  5)  if the temperature of a substance changes by 100k, by how much does it change in celcius?  6) if the mass of 0ml of water is 1kg, what is the mass of 1ml of water?  7) round 0.030490 to 3 significant figures and express it in scientfic notation ? for q4, if i'm not wrong, the answer is (-269degrees celsius).