Is freezing water a physical or chemical change

Scientists are often interested in knowing the molar heat of combustion – the heat released during the combustion of one mole of a substance. use the periodic table to find molar masses. how many moles of ethanol are present in the sample?

Can anyone answer these questions? ? i need it before 1: 00pm today

Achemist needs to prepare a buffer solution of ph 8.80. what molarity of nh3 (pkb = 4.75) is required to produce the buffer solution if the (nh4)2so4 in the solution is 1.8 m?