Question

procedure 1|100.0 g|97.5 g
procedure 2|100.0 g|102.5 g
assuming the students did not make any careless errors, what likely explains these changes in mass?
procedure 1: all the reactants were liquids that evaporated.
procedure 2: a gas was formed as one product, and it escaped into the air.
procedure 1: one of the reactants was converted to thermal energy.
procedure 2: all the products were liquids.
procedure 1: one of the products was a gas that escaped into the air.
procedure 2: a gas from the air reacted with one of the other reactants.
procedure 1: the reactants were liquids with different densities.
procedure 2: the reactants were combined into only one product.

Explanation:

In a chemical reaction, mass can change if a gas is formed and escapes (decrease in mass) or if a gas from the air reacts with the reactants (increase in mass). In Procedure 1, a decrease in mass likely means a gas product escaped. In Procedure 2, an increase in mass likely means a gas from the air reacted with one of the reactants.

Answer:

Procedure 1: One of the products was a gas that escaped into the air.
Procedure 2: A gas from the air reacted with one of the other reactants.