Unscented and scented candles both burn for an equal amount of time. As long as the scented candle is made properly, the only difference between how the candles burn is the fragrance released.
Scented candles don't burn correctly if too much fragrance is added. Candle flames produce water vapor and carbon dioxide. Candles are composed of wax and a wick, with dyes added for colored candles. Candles were originally created using whale fat. The first known use of candles was in China around 200 B.C. Candles have been used to provide light sources and tell time. Other uses include religious ceremonies and aromatherapy.