Students can sort examples like rusting iron and melting ice by coloring the gumballs pink for chemical changes or blue for physical changes.

To solve this worksheet, we need to look at each example inside the gumball machine and decide if it is a Chemical Change or a Physical Change.

Here is the rule:
* Physical Change (Blue): The object changes shape, size, or state (like melting or freezing), but it is still the same stuff. You can often reverse these changes.
* Chemical Change (Pink): A new substance is created. This usually involves heat, light, gas (bubbles), a color change, or a smell change. You usually cannot turn it back into what it was before.

Let's go through them one by one:

1. Iron rusting: Rust is a new substance formed when iron mixes with oxygen. (Chemical / Pink)
2. Saltwater: Mixing salt and water doesn't create a new chemical; you can evaporate the water to get the salt back. (Physical / Blue)
3. Chopping wood: The wood is just in smaller pieces. It is still wood. (Physical / Blue)
4. Color change: In science, a sudden color change usually means a chemical reaction happened. (Chemical / Pink)
5. Freezing: Water turning to ice is just a change of state. It is still water. (Physical / Blue)
6. Digesting food: Your body uses chemicals to break food down into energy and waste. New substances are made. (Chemical / Pink)
7. Oil and water: They don't mix well, but they don't react to become something new. (Physical / Blue)
8. Food rotting: Rotting creates new smelly gases and substances. It is a chemical breakdown. (Chemical / Pink)
9. Breaking an egg: Cracking the shell and spilling the yolk is just a physical mess. It’s still egg. (Physical / Blue)
10. Cutting hair: Your hair is shorter, but it is still hair. (Physical / Blue)
11. Temperature change: Getting hot or cold is a physical property change. (Physical / Blue)
12. Baking a cake: The batter turns into a fluffy cake through heat. You can't un-bake a cake. (Chemical / Pink)
13. Fireworks: Explosions create light, heat, and smoke. New chemicals are formed. (Chemical / Pink)
14. Breaking glass: The glass is shattered, but it is still glass. (Physical / Blue)
15. Ice melting: Solid water turns to liquid water. It is still H2O. (Physical / Blue)
16. Mixing salt and sand: They are just sitting next to each other. No reaction. (Physical / Blue)
17. Cooking chicken: Heat changes the proteins in the meat. It is no longer raw chicken. (Chemical / Pink)
18. Bubbles forming: Bubbles usually mean a gas is being released from a chemical reaction. (Chemical / Pink)
19. Folding paper: The paper is bent, but it is still paper. (Physical / Blue)
20. Burning fire: Burning turns wood or fuel into ash and smoke. (Chemical / Pink)
21. Condensation: Water vapor turning into liquid water droplets. Still water. (Physical / Blue)
22. Odor change: A new smell usually means a new chemical substance has been created. (Chemical / Pink)

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Final Answer:

Color PINK (Chemical Change):
* Iron rusting
* Color change
* Digesting food
* Food rotting
* Baking a cake
* Fireworks
* Cooking chicken
* Bubbles forming
* Burning fire
* Odor change

Color BLUE (Physical Change):
* Saltwater
* Chopping wood
* Freezing
* Breaking an egg
* Cutting hair
* Oil and water
* Temperature change
* Ice melting
* Mixing salt and sand
* Breaking glass
* Folding paper
* Condensation