Roots take in water and dissolved minerals. Stems support the plant and transport materials. Green leaves can use light energy, water and carbon dioxide from air to make sugars. This process is photosynthesis. Soil supplies minerals, but it is not the plant's ready-made sugar meal.
Worked example
Think of a green leaf as a tiny food factory. Light supplies energy; water and carbon dioxide are materials used to make sugar. The comparison helps explain the job, but a leaf has living cells, not tiny cooks.
Draw the Inputs
Draw a green plant with roots, a stem and leaves. Add an arrow for water entering the roots and arrows for light and carbon dioxide reaching a leaf. Label sugar as food made by the plant. Use paper only: do not block a real plant's light or water to test the idea. This model leaves out many smaller processes.