For a science project, I set hairspray or dry shampoo on fire. I put them on the concrete. the shampoo would only burn when I kept the flame on it. the dry shampoo burned fine. I tried the same on a metal pan and got opposite results. why is that?

 It's great that you're conducting experiments and making observations! However, it's important to emphasize safety when experimenting with flammable materials like hairspray and dry shampoo. Never conduct such experiments without adult supervision and proper safety measures in place.

Now, regarding your observations:

The difference in burning behavior between hairspray and dry shampoo likely stems from their chemical composition and flammability characteristics. Here's a breakdown:

Hairspray:

• Typically contains propellants like hydrocarbons (butane, propane) and alcohols (ethanol) as main flammable ingredients.
• These propellants are volatile, meaning they easily evaporate and form flammable vapors at room temperature.
• On both concrete and metal, the readily available vapors ignite easily with the flame, sustaining the fire even after briefly removing the source.

Dry shampoo:

• Usually contains starch (often rice starch) as the main ingredient, with propellants and fragrances in smaller amounts.
• Starch generally has lower flammability compared to hydrocarbons and alcohols.
• On concrete, the limited flammable components might require sustained flame contact for ignition, explaining why the fire doesn't continue after removing the flame.
• On the metal pan, the heat conducted by the metal might aid in igniting the dry shampoo more readily, even with its lower flammability.

Remember:

• Experimenting with flammable materials can be dangerous. Always prioritize safety and conduct such experiments under adult supervision.
• The exact chemical composition of different brands can vary, potentially affecting their burning behavior.
• It's important to research the properties of the materials you're using before conducting experiments.

Further exploration:

• You could research the specific ingredients in the hairspray and dry shampoo brands you used and compare their flammability properties.
• Explore the role of the metal pan in conducting heat and its influence on flammability.
• Remember to prioritize safety and responsible experimentation practices in future endeavors.