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Questions in chemistry

[Done] What is a property that describes how easily a substance undergoes chemical changes?

[Done] A plant uses the energy from sunlight to create oxygen and glucose from carbon dioxide and water. Which statement is true about the changes that have occurred? A. A chemical change has occurred because energy was needed. B. A physical change has occurred because the substances are still gases. C. A physical change has occurred because the plant looks different. D. A chemical change has occurred because new compounds have been produced.

[Done] Which is easier to observe, physical or chemical properties? Why?

[Done] Is the element Americium a metal, metalloid, or nonmetal?

[Done] Explain how mass and energy are conserved when water evaporates.

[Done] What element is used as a shield to protect people from radioactive substances?

[Done] When two pure substances are combined so that each retains its own properties, the result is a(n)? A. mixture B. isotope C. element D. compound

[Done] When you add heat to a liquid or gas, what happens to the density, and why?

[Done] A ____ farm can be used to generate electricity. A. solar B. geothermal C. wind D. hydroelectric

[Done] Which of the following must crystalline solids have? A. Carbonates B. Cubic structures C. Orderly arrangement of atoms D. Cleavage