Which of the following is a chemical change? A. Water freezing to form ice
B. Sugar dissolves in water
C. Gasoline burns in a car engine
D. A piece of metal expands when it is heated

C. would be the correct option.

Explanation:

Burning gasoline is a chemical change because when gasoline is ignited, water and carbon dioxide are produced. Water freezing to form ice would be a physical change since its state of matter has changed, but not the water itself. Sugar dissolving in water is also a physical change because all it's really doing is just forming bubbles and changing the color. Choice D. would also be a physical change since the piece of metal is still a piece of metal, it just expanded when the temperature increased.

electron microscopy and scanning tunneling microscopes gives us a greater understanding of atoms by being able to see the atom itself, and lets us see some atomic reactions.

explanation:

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

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