When a plant grows its mass increases over time. does this mean that new matter is created?

No, new matter is not created when a plant grows; instead, the increase in mass comes from the uptake of water, carbon dioxide, and nutrients from the soil. Through the process of photosynthesis, plants convert carbon dioxide and sunlight into glucose, which contributes to their growth. The mass increase is a transformation and rearrangement of existing matter rather than the creation of new matter.