化學問題.................................

(matter) and (substance) are related to both Physics and Chemistry.
In physics, matter is commonly defined as the substance of which physical objects are composed, not counting the contribution of various energy or force-fields, which are not usually considered to be matter per se (though they may contribute to the mass of objects). Matter constitutes much of the observable universe, although again, light is not ordinarily considered matter. Unfortunately, for scientific purposes, "matter" is somewhat loosely defined. Regarding this difficulties concerning the definition of "matter", V.I. Lenin in his work "Materialism and empiriocriticism" proposed to define "matter" as the objective reality, which is given in our senses and is reflected by them.
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A chemical substance is a material with a definite chemical composition. It is a concept that became firmly established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate.[1] He deduced that: "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound". This became known as the law of constant composition[2]. Later with the advancement of methods for chemical synthesis particularly in the realm of organic chemistry; the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry, the concept was defined as is found in most chemistry textbooks. However, there are some controversies regarding this definition mainly because the large number of chemical substances reported in chemistry literature need to be indexed.
A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. A pure chemical substance cannot be separated into other substances by a process that does not involve any chemical reaction and is rarely found in nature. Some typical chemical substances can be diamond, gold, salt (sodium chloride) and sugar (sucrose). Generally, chemical substances exist as solid, liquid, or gas, and may change between these phases of matter with changes in temperature or pressure.
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Also, a chemical substance can either be a pure chemical element or a pure chemical compound. However, there are exceptions to this definition, a pure substance can also be defined as a form of matter that has both definite composition and distinct properties. and the chemical substance index published by CAS also includes several alloys of uncertain composition.

Matter 同 substance 冇咩唔同 .