Synthesized answer
Homogeneity alone is not sufficient to classify a substance as a compound because mixtures can also be homogeneous. The text states that "A substance is said to be homogeneous when no one part of it differs from any other part in composition. But this may be predicated of glass, or of air, which are mixtures, and not compounds. A mixture may be homogeneous; a compound must" [3]. This highlights that while a compound is always homogeneous, a homogeneous substance is not necessarily a compound.
For example, the atmosphere is described as a mixture of gases, including nitrogen, oxygen, and argon, and it is stated that "each gas retains its individual properties" [1]. The atmosphere is considered homogeneous, yet it is classified as a mixture. Similarly, the text mentions that alloys can be mixtures, and "As such mixtures are usually homogeneous, it is often a matter of great difficulty to identify the definite compounds" [2]. This demonstrates that a homogeneous appearance does not preclude a substance from being a mixture.
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From the book
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…
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…
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 "…
tin against platinum. A chemical compound of tin and copper, however, would have a less electromotive force than free tin ; and as the tin in the alloy mentioned is dissolved away, the electromotive force will suddenly fall when the excess of tin has been dissolved, until it is equal to that of the chemical compound against platinum. An analysis of the alloy at this stage will reveal the com- position of the compound. In this way the existence of a compound of the formula CugSn was detected.
Although the external properties of the elements does not show any obvious relation to their order in the periodic table (see Part I.), yet it may be generally remarked that the density increases as each column is descended. Among the lightest of the elements are lithium, beryllium, magnesium, and aluminium, at least in the solid state ; whereas osmium, iridium, platinum, and gold are among the heaviest. But much more must be ascertained regarding their properties before a satisfactory comparison can be made. CHAPTER II Classification of Compounds — The Hydrides. Classification of…
More questions about this book
- How did the historical lack of distinction between mixtures and compounds, and John Dalton's subsequent formulation of laws, fundamentally alter the scientific approach to classifying chemical substances?
- 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?