When the gravimeter was invented.​

1934

Explanation:

In 1934, Dutch geophysicist Felix Meinesz invented the gravimeter, a device that measures the strength of gravity at a location. This new technology allowed the size of Hawaii to be measured. Extending from the highest point, Mauna Kea, to the ocean bottom, the main island of Hawaii is 56,000 ft. high, twice the height of Mt. Everest.                                                                                  Hope this helps! :P

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.