Which of the following will have its mass increased when heated in air?

When materials are heated in air, they can undergo a variety of chemical reactions such as combustion, oxidation, or decomposition. These reactions can result in a change in the mass of the material. Out of the options provided, the material that is most likely to have its mass increased when heated in air is "Magnesium". This is because magnesium is a reactive metal that undergoes combustion in air, which means it reacts with oxygen in the air to form magnesium oxide. The magnesium oxide has a greater mass than the original magnesium metal, so the overall mass of the system increases. Helium is a noble gas and is chemically inert, which means it does not react with other substances under normal conditions, including when heated in air. Therefore, its mass remains the same. Copper pyrites is a mineral composed of various compounds, including copper and sulfur. When heated in air, it can undergo various chemical reactions, but none of these reactions result in an overall increase in mass. Glass is a non-crystalline solid that is formed by heating a mixture of silica, soda, and lime. When heated further in air, it may undergo some minor chemical reactions, but these do not result in a significant increase in mass. Therefore, out of the options provided, magnesium is the material that is most likely to have its mass increased when heated in air.