I do not agree with the statement.
The "substance" can be a compound. It's "pure"
as long as there's nothing else in it but its name.
'Pure' water is 100% H₂O with nothing else in it.
'Pure' table salt is 100% NaCl with nothing else in it.
'Pure' carbon dioxide is 100% CO₂ with nothing else in it.
These example substances are all compounds, not elements.
C. amphibian eggs do not contain a protective shell
Positively charged protons in the nucleus of the gold atom .... rutherford scattering ???
The lemon battery hypothesis states that a lemon is acidic enough to carry an electric charge and act as a battery.
