Answer:
Decrease
Step-by-step explanation:
Density is defined as the mass per unit volume. Density is highly influenced by temperature.
The density of metals and copper is inversely proportional to the temperature, it means density of copper decreases with an increase in temperature or when heated. This is so because when the copper is heated, the copper atoms start vibrating faster that allows the collision of atoms with each other faster and occupying more volume than before. As the copper atoms occupy more volume, the density of copper decreases.
Hence, the correct answer is "On applying heat the density of copper decreases".