Final answer:
The statement is false because it contradicts the Law of Definite Proportions, which dictates that a chemical substance always includes the same proportions of elements by mass, such as in water, sodium chloride, and sucrose.
Step-by-step explanation:
The statement that in a given type of chemical substance, the elements never combine in the same proportions by mass is FALSE. This statement goes against the well-established Law of Definite Proportions, which asserts that a chemical substance always contains the same proportions of elements by mass. This foundational principle was established by the French scientist Joseph Proust and is also referred to as the law of constant composition.
For example, water (H2O) will always consist of 11.19% hydrogen and 88.81% oxygen by mass, regardless of its source or how it was prepared. Similarly, common table salt (sodium chloride - NaCl) consistently contains 39.34% sodium and 60.66% chlorine by mass, while sucrose (table sugar - C12H22O11) contains 42.11% carbon, 6.48% hydrogen, and 51.41% oxygen by mass. These proportions are fixed and do not vary from sample to sample, reflecting the underlying atomic structure and ratios of the compounds.