A sample that cannot be separated into two or more substances by physical means is a compound. A compound is made up of 2 or more elements which cannot be broken down by physical means.
A mixture is a sample of matter that can be separated into different substances by physical means. This can include techniques such as filtration, distillation, or chromatography to isolate the individual components.
The defining characteristic of a pure chemical substance is that any sample of it contains the same elements in the same mass proportions to one another.
Matter is a pure substance if it can only be separated by chemical means, NOT physical means. This could be a compound or an element. The opposite is a mixture which can be separated/broken into smaller parts by physical means.
Anything larger than a single atom. Compounds -- that is, substances chemically made from more than one species of atom -- can be chemically separated into their elemental parts. H2O can be seperated by electricity into H2 and O2. 2(H2O) + charge --> 2H2+O2
No, pure substances cannot be mixtures. A pure substance is made up of only one type of atom or molecule, with uniform properties throughout the sample. Mixtures, on the other hand, are composed of two or more different substances physically combined, each retaining its individual properties.
chemical change
Any particular isolated sample of a mixture has a definite chemical composition, but the general idea of a mixture, even of the same materials, implies variability in possible chemical composition.
For chemical reactions, the elements in a sealed vessel will not change. But, reactions can take place that would tend to take the sample to a state of equilibrium. Or, with heating or cooling the physical state can be changed.Another type of reaction is nuclear decay, in which radioactive substances will spontaneously decay to other radioactive substances, or decay to non-radioactive substances, thus actually changing the elements present.
Melting a sample of gold is an example of a physical change.
Resolving a mixture of compounds refers to the separation or purification of different substances within a mixture. This process is often done using techniques like chromatography or distillation to isolate individual compounds based on their physical or chemical properties.
- place a sample in a refrigerator- place a sample in liquid nitrogen
not usually unless they prescribe you a medication that you cannot take while pregnant; or if your doing a physical