During the process of iron rusting, an iron atom combines with oxygen atoms. What is the identity of that original iron atom after the reaction is complete?

It has been transformed into an oxygen atom.

It is still an iron atom, but it is now bonded differently.

It has been destroyed and converted into energy.

It has become a new, fundamental type of atom called a 'rust' atom.

A hydrogen atom from a water molecule (H₂O) is used by a plant during photosynthesis to help create a sugar molecule (C₆H₁₂O₆). Which statement accurately describes the hydrogen atom?

The hydrogen atom was converted into a carbon atom.

The hydrogen atom retained its identity throughout the process.

The hydrogen atom was broken down into smaller particles.

The hydrogen atom merged with an oxygen atom to form a new element.

The atom would be a carbon atom at all times.

The atom would change into a nitrogen atom in the animal.

The atom would be destroyed and remade at each step.

The atom would temporarily become an oxygen atom in the atmosphere.

Because the atoms change their size and mass.

Because the atoms rearrange themselves into new repeating groups or molecules.

Because the number of protons in the atoms' nuclei changes.

Because the original substance's atoms are replaced by new atoms from the air.

The building blocks get smaller, while the substance gets larger.

The building blocks (atoms) are destroyed, while the substance is created.

The building blocks (atoms) remain the same, while the substance (their arrangement) changes its properties.

The building blocks change identity, while the substance maintains its original properties.