Grass growing is primarily a chemical change. This is because the process involves several chemical reactions that transform the raw materials (such as water, carbon dioxide, and sunlight) into glucose and oxygen through photosynthesis. These chemical reactions result in the formation of new substances, which is a key characteristic of a chemical change.
During photosynthesis, the grass absorbs sunlight, water, and carbon dioxide. The chlorophyll in the grass cells captures the sunlight and uses its energy to convert water and carbon dioxide into glucose and oxygen. The glucose is then used by the grass as an energy source to grow, while the oxygen is released into the atmosphere.
While there are physical changes involved in grass growing, such as the increase in size and the development of new leaves, these changes are secondary to the chemical processes that drive the growth. Therefore, the primary nature of grass growing is a chemical change.