Synthesized answer
According to the passages, in the olden days, no distinction was drawn between a compound and a mixture, and all impure substances were termed "mixts" [2]. It was only after Dalton formulated the laws that go by his name that the distinction was drawn [2]. The ultimate criterion for combination became definiteness of proportion, which is generally connected with uniformity in properties, or homogeneity [2].
This fundamentally altered the scientific approach to classifying chemical substances by establishing a clear, law-based criterion: a compound must have a definite proportion of elements, while a mixture may be homogeneous but lacks this fixed composition [2]. The passages note that even after this distinction, practical classification can still be difficult—for example, a solution of carbon dioxide in water is considered a compound, while sugar in water is a mixture, requiring guidance by analogy [1]. Similarly, alloys may be definite compounds, mixtures, or mixtures of compounds with components, and homogeneity can make identification challenging [3].
Thus, Dalton's laws provided the theoretical foundation for distinguishing mixtures from compounds based on definite…
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Again, it is usually accepted that the separation of the constituents of a mixture may be effected by mechanical, or at least by physical means ; whereas the separation of the elements from a compound require chemical treatment. Here it is difficult to draw a sharp distinction. The VOL. II. A 2 MODERN CHEMISTRY separation of carbon dioxide from soda-water by the appli- cation of heat is similar in character to the separation of sugar from water by evaporation of the water ; yet we believe that a solution of carbon dioxide in water consti- tutes a compound, while that of sugar in…
Title: Modern Chemistry by William Ramsay fcresenteD to of tbe of {Toronto Mrs. W. E. -U vl THE TBMPLB PRIMERS MODERN CHEMISTRY Systematic By WILLIAM RAMSAY, D.Sc. !E JOHN DALTON mODERH CHEMISTRY SYSTEMATIC RAmSAY-DS? 1900* t9&SO BEDFORD-STREET 1 ' . All rights reserved ' /, MODERN CHEMISTRY SECOND PART SYSTEMATIC CHEMISTRY CHAPTER I Methods of Preparing Elements — Their Physical Properties. Mixtures and Compounds. — In the olden days, no distinction was drawn between a compound and a mixture. Indeed, all " impure " substances artificially prepared were termed "…
Classification. — Alloys in general may be classified under two heads : ( I ) definite compounds, in which the elements are present in atomic proportions; and (2) mix- tures in which combination has not taken place. To these classes may be added a third — mixtures of definite com- pounds with one or other of the components of the alloy. As such mixtures are usually homogeneous, it is often a matter of great difficulty to identify the definite compounds. In many cases, too, it would appear that one of the metals in the alloy is present in an allotropic form ; for example, on…
hen estimated by known processes. It was thus possible to find the ratio of the combined to the uncombined hydro- gen. Now, it was discovered many years ago that the rate of chemical change depends on the amount of each of the reacting substances present in unit volume — a condition ex- pressed by the term "active mass." Thus, if we double the amount of hydrogen in the mixture of the gases men- tioned, we double its " active mass." Let /«, denote the number of molecules in unit volume of the iodine gas, and ^2 that of the hydrogen, and let ^hi be that of the hydrogen iodide formed…
Alloys. — The word "alloy" was originally applied to mixtures of gold and silver with other metals ; it now signifies any mixture or compounds of metals with each other ; alloys of mercury are, however, termed " amal- gams." When two metals are melted together, they 192 MODERN CHEMISTRY always mix, more or less. Some may be mixed in any desired proportion, such as lead and tin ; others are par- tially soluble in each other ; zinc, for example, dissolves 1.6 per cent, of lead, and lead 1.2 per cent, of zinc ; but on stirring up the metals together, there is always a layer at the top…
More questions about this book
- The text states that "a mixture may be homogeneous; a compound must." Explain why homogeneity alone is not a sufficient criterion to definitively classify a substance as a compound, using examples from the text.
- Why does the author suggest that the separation of carbon dioxide from soda-water indicates a compound (carbonic acid), while the separation of sugar from water indicates a mere mixture, despite both separations involving heat? What specific chemical principle or "analogy" guides this distinction?
- Using the provided evidence for the atmosphere, explain why it is classified as a mixture rather than a compound, focusing on the properties of its gaseous constituents and how this simplifies the classification problem compared to other types of substances.
- Based on the challenges and nuances presented in the text, what are the two most crucial criteria you would use to distinguish between a mixture and a compound, and what are the primary difficulties or exceptions you would highlight when applying these criteria?