Upon strong heating, copper powder forms a black solid. This chemical change is best described as:

The correct option is Oxidation of copper to form copper(II) oxide.

Explanation

When metals are heated in the presence of air, they react with oxygen to form metal oxides. In chemical terms, the addition of oxygen to a substance is defined as oxidation.

Detailed Analysis:

• Chemical Process: Copper (Cu) is a reddish-brown metal. When heated strongly in air, it combines with oxygen (O₂) to form Copper(II) oxide (CuO).
• Reaction Equation:
  2Cu (s) + O₂ (g) → 2CuO (s)
• Observation: The reddish-brown copper powder turns into a black solid. This black substance is Copper(II) oxide.
• Classification: Since copper gains oxygen during this reaction, it is said to be oxidized. Therefore, the reaction is an oxidation reaction.

Option Analysis:

• Oxidation of copper to form copper(II) oxide is Correct: It accurately describes the process as oxidation and identifies the black solid as Copper(II) oxide.
• Reduction of copper to form copper(I) oxide is Incorrect: Reduction involves the loss of oxygen. Additionally, Copper(I) oxide (Cu₂O) is typically red, not black.
• Options Hydrogenation of copper surface and Dehydrogenation of copper lattice are Incorrect: Hydrogenation and dehydrogenation involve the addition or removal of hydrogen, which is not present in this reaction.

Key Takeaway:
Heating copper powder in air results in the oxidation of copper, transforming the reddish-brown metal into black Copper(II) oxide (CuO).