A student is comparing physical versus chemical changes using sugar cubes. Which part of the student's experiment illustrates a chemical change?

A
Melting a sugar cube using a hotplate

B
Burning a sugar cube in a flame

C
Dissolving a sugar cube in water

D
Crushing a sugar cube with a mortar and pestle

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.

Which is a function performed by stem cells in the skin a. replacing lost skin cells b. making cells for the intestines c. growing new organs d. differentiating into brain cells plz apex

List five ways we are indebted to phytoplankton