Why are phase changes considered physical and not chemical changes? 1. Phase changes as a liquid or solid are physical but not considered chemical like gas.

2. Phase changes require a lot of energy, which is physical and not chemical.

3. There are no chemicals found inside matter, so they must be physical because we can see them.

4. Matter can change between phases, so they are reversible physical changes that do not change matter’s chemical composition.

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.

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