The number of times a machine multiplies the effort force is the what of the machine

According to the law of conservation of mass, in a chemical reaction the total starting mass of all the reactants equal the total final mass of all the products. true or false?

If anyonee has done the momentum lab practical in physics can you give me the answers i am s lostt rnn : (

If you visited mount shasta city (elevation 900 m [3000 ft.]) and found the outside air temperature to be 27°c (81°f), what would be the air temperature at the summit of mount shasta (elevation 4200 m [14,000 ft.]) at that moment-assuming that the temperature conditions with altitude change at an average, or normal, lapse rate?