0.0136 g + 2.70 × 10-4 g - 4.21 × 10-3 g = ? how many digits to the right of the decimal point should be used to report the result?

In my opinion, the most logical option is either to write the term so that the g has no decimal or 1 decimal number

Heat is involved in chemical change in two ways; chemical changes either result in heat being added to or removed from an object, and chemical changes require a certain amount of heat before they can take place.