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------------------------------------------------ Which of these statements accurately describes the various classes of fire extinguishers?

A. Class A extinguishers are suitable for electrical fires.
B. Class B extinguishers are for flammable liquid fires.
C. Class C extinguishers handle ordinary combustibles.
D. Class D extinguishers combat combustible metals.

Class A extinguishers are suitable for ordinary combustibles, Class B extinguishers are for flammable liquid fires, Class C extinguishers handle electrical fires, and Class D extinguishers combat combustible metals. So the correct answer is option A).

Explanation:

A) Class A extinguishers are suitable for ordinary combustibles such as wood, paper, and cloth. B) Class B extinguishers are for flammable liquid fires like gasoline and oil. C) Class C extinguishers are designed to handle electrical fires. D) Class D extinguishers are specifically for combustible metals like magnesium and titanium.

Physical and chemical changes involve the transformation of substances. A chemical change results in the formation of new substances, whereas a physical change does not. Burning coal is a chemical change. Melting ice, changing the volume of oxygen gas with temperature, and magnetizing a screwdriver are examples of physical changes. An explosion of a firecracker represents a chemical change because new substances are formed.

Intensive and Extensive Properties:

Extensive properties depend on the amount of substance present, such as mass and volume. In contrast, intensive properties are independent of the amount of substance, such as density or melting point.