Why do the properties of a pure substance not vary from sample to sample

Acamcorder has a power rating of 17 watts. if the output voltage from its battery is 7 volts, what current does it use?units:

In the following table, all the columns for the element calcium are filled out correctly. element electron structure of atom electron structure of ion net ionic charge calcium 1s22s22p63s23p64s2 1s32s22p63s23p64s1 +1 true false

Answer asap need by wednesday morning calculate the ph of 0.036m naoh best answer will be brainliest