Acetylene, with the chemical formula C2H2, is considered a pure substance. Pure substances are characterized by having a fixed composition and distinct chemical properties. Acetylene perfectly fits this description as it consists of only two elements, carbon and hydrogen, combined in a constant 1:1 ratio by mole, forming a compound with very specific chemical and physical properties. Unlike mixtures, which are a physical combination of two or more substances, each retaining its own properties, the properties of acetylene are uniform and do not vary. Additionally, pure substances can be elements or compounds. Since acetylene is made up of more than one type of element chemically bonded together, it is classified as a compound, thus reinforcing its status as a pure substance.

Dyeing hair bundles honey brown requires a careful and precise approach to ensure even, long-lasting color. Firstly, select a high-quality hair dye in the desired honey brown shade, ensuring it's suitable for the hair type of your bundles. It's recommended to perform a strand test to preview the results. If your bundles are dark, you might need to lighten them with a bleach kit before applying the honey brown dye, following the manufacturer's instructions for both processes. Always wear gloves and protect surfaces. After dye application, wait for the specified time, then rinse out the dye until the water runs clear. Follow with a deep conditioning treatment to keep the hair moisturized and lock in the color. Regular maintenance and care with color-safe products will help prolong the vibrancy of your honey brown bundles.

Black polypropylene is more UV resistant than its non-black counterparts due to the addition of carbon black, a common UV stabilizer. Carbon black acts by absorbing UV radiation, converting it into heat, and thereby minimizing the polymer's degradation rate when exposed to sunlight. This enhancement allows black polypropylene to maintain its structural integrity and mechanical properties for longer periods when used in outdoor applications. However, it is vital to note that while the presence of carbon black improves UV resistance significantly, it does not render the material completely invulnerable to UV damage. Prolonged exposure to intense UV radiation can still lead to some level of degradation over time. Manufacturers often specify the expected lifespan of their products based on typical environmental exposure conditions.