Answer:
Most solar cells are made from silicon—the same semiconductor material that is at the heart of computers. The cells are expensive to produce because it takes a great deal of energy to purify the silicon.
Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size. These physical properties are the result of the processes that formed the rocks.Or how they form
Hope dis helps
Two physical changes is:
• Breaking
• Boiling
Two chemical changes could be:
• Molecules rearranging with other molecules to make new substance
• Bubbling/fizzing
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