A student wants to examine a substance without altering its composition. Which of the following describes a property of the substance that the student should examine? Toxicity, because it can be observed by altering the state of the substance
Boiling point, because it can be observed by altering the state of the substance
Toxicity, because it can be observed by replacing the atoms of the substance with new atoms
Boiling point, because it can be observed by replacing the atoms of the substance with new atoms

Boiling point, because it can be observed by altering the state of the substance

Explanation:

Physical property is defined as the property of a substance which becomes evident during physical change in which there is alteration in shape, size etc. No new substance gets formed during physical change. Example: Melting point

Chemical property is defined as the property of a substance which becomes evident during chemical change in which a change in chemical composition takes place. A new substance is formed in these reactions. Example: Reactivity with other substances

Thus Boiling point is a propertywhich can be examined without altering the composition, because it can be observed by altering the state of the substance

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).