A sample of matter contains two different elements joined together to form molecules. There is only one type of molecule

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A sample of matter contains two different elements joined
together to form molecules. There is only one type of molecule
present in the sample. Heat is applied to the sample and a change
occurs. Bonds of the reactant are broken and new bonds form to make
products. What can we say about the sample and how it changed?
a. This was a compound that underwent a chemical change
b. This was a homogeneous mixture of elements that underwent a
chemical change
c. This was a compound that underwent a physical change
d. This was a homogenous mixture of elements that underwent a
physical change