Which properties, physical or chemical, were most useful in identifying the mystery powder? explain your answer.

The answer depends on what substances you were testing, but here are some ideas.

If all of them were white as in the typical experiment, then color is not very useful.  If you were allowed to taste them, then a salty taste would be a helpful clue.  If the textures were different, some crystals, like salt or sugar and others powdery, like flour or cornstarch, those properties would be helpful.  If some dissolved in water,...

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml