Plants use simple chemical substances like carbon dioxide, water, and minerals for the synthesis of food through the process of photosynthesis.

**Photosynthesis:**
Photosynthesis is the process by which plants convert light energy from the sun into chemical energy in the form of glucose. This process takes place in the chloroplasts of plant cells and involves several steps.

**Carbon Dioxide:**
Plants obtain carbon dioxide from the air through tiny pores called stomata present on the surface of leaves. Carbon dioxide is an essential raw material for photosynthesis. During photosynthesis, carbon dioxide combines with water to produce glucose.

**Water:**
Water is another crucial raw material required for photosynthesis. Plants absorb water from the soil through their roots and transport it to the leaves. In the leaves, water molecules are split into hydrogen and oxygen during a process called photolysis. The hydrogen is then used to produce glucose.

**Minerals:**
Plants also require minerals for their growth and development. These minerals are absorbed from the soil through the roots. Some essential minerals needed by plants include nitrogen, phosphorus, potassium, calcium, and magnesium. These minerals play important roles in various biochemical reactions within the plant, including the synthesis of proteins and enzymes.

**Synthesis of Food:**
During photosynthesis, plants use the energy from sunlight to convert carbon dioxide and water into glucose. Glucose is a simple sugar that serves as the primary source of energy for plants. It is also used to produce other organic molecules, such as starch, cellulose, and proteins. These organic molecules are essential for the growth and development of plants.

Thus, plants utilize carbon dioxide, water, and minerals to synthesize food through the process of photosynthesis. This process allows plants to convert light energy into chemical energy, which is stored in the form of glucose and other organic molecules. These synthesized food substances are vital for the survival and growth of plants.