Taylor was thirsty and decided to mix up a pitcher of lemonade. she put lemon juice, water, and sugar into a pitcher and stirred it to create this wonderful new drink. how could taylor decide if she just created a mixture or a compound?

Answer is: it must be a mixture as she can separate all of the individual ingredients.

Pure substance is made of only one type of atom (element) or only one type of molecule (compound), mixtures and solutions are made from two or more types of pure substances.  

Elements (for example copper, iron, sulfur) and compounds (water, sodium chloride) have definite and constant composition with distinct chemical properties.  

Pure substances can be separated chemically, not physically, that is difference between pure substances and mixtures.

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).