This sounds like a fun chemistry demonstration, but there's no single chemical equation that describes the entire process. Here's why:

The Chemistry at Play

* Initial Reaction: The granulated zinc reacts with the sodium hydroxide solution to form sodium zincate (Na₂ZnO₂) and hydrogen gas.

```

Zn(s) + 2NaOH(aq) + 2H₂O(l) → Na₂ZnO₂(aq) + 2H₂(g)

```

* The Silver Color: The copper penny (primarily copper) reacts with the zincate ions in solution to form copper(I) oxide (Cu₂O), which appears silver.

```

Cu(s) + Na₂ZnO₂(aq) + H₂O(l) → Cu₂O(s) + Zn(s) + 2NaOH(aq)

```

* The Gold Color: Upon heating, the copper(I) oxide is further oxidized by the air, forming copper(II) oxide (CuO) which has a reddish-brown or golden appearance.

```

Cu₂O(s) + ½O₂(g) → 2CuO(s)

```

Important Considerations:

* The Reaction is Complex: This demonstration involves multiple reactions happening in sequence. It's not a simple one-step process.

* Incomplete Reactions: The silver and gold appearances are not pure metals. They are oxides of copper.

* Safety: Be cautious with sodium hydroxide, as it is a strong base.

Overall, the "silver" and "gold" colors you observe are due to the formation of copper oxides, not elemental silver or gold.