[fatimasaboor123]

A chemical substance, also known as a pure substance, is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions or alloys. -Wikipedia(Chemical Substance)

The bold sentence says that alloys are substances. But according to the definition of alloy:

An alloy is a mixture of metals or a mixture of a metal and another element. - Wikipedia (Alloy)

In chemistry, a mixture is a material made up of two or more different substances which are mixed but are not combined chemically. - Wikipedia (Mixture)

My question is what is an alloy??? a substance or a mixture?

[Borek]

As much as I like wikipedia, it can be occasionally misleading or confusing.

Alloys - in general - are mixtures, buy they can contain compounds (intermetallic, or of metals and non-metals, like cementite in steel). Add to that fact that not all compounds have a well defined stoichiometry and you have a confusion waiting to happen.

[Arkcon]

I think the biggest problem is your first definition:

A chemical substance, also known as a pure substance, is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions or alloys. -Wikipedia(Chemical Substance)

That's a clear statement, made up of true concepts.  But what does it mean?  Reading that, I know what a chemical substance means, but not what it is.  Is a computer a chemical substance?  Probably not.  But is a computer case a chemical substance?  Its generally metal (a element or an alloy) glued or fastened to a plastic (a mixture of chemicals) and painted (with a mixture.)  So is that a chemical substance?

If I layer, on top of each other a number of different alloys, sometimes putting in between them nonmetallic mixtures, and seal them in a known organic polymer, is that a chemical substance?  Because I crudely described a computer chip, and we generally don't think of them that way.  Either everything is a chemical substance, or nothing is.

I suppose, if I mix water, some polymers, some mixtures of lipids, I could make hair conditioner, and that's a chemical substance, because the mixture of mixtures has its own physical properties, distinct from the components, and distinct from other mixtures.  So maybe that's what the definition is meant to be used for?

[Enthalpy]

A chemical substance [...] cannot be separated into components [...] without breaking chemical bonds.
[...] A mixture is [...] made up of [...] substances which are mixed but are not combined chemically.
[...] what is an alloy??? a substance or a mixture?

The elements that make an alloy are bond chemically. A piece of metal is one big molecule.

Alloying metals takes or releases little energy and involves stirring the liquids in a pot. That can be reasons to call it "mixture", properly or not.

[dew3554]

As others have said, an alloy is just a mixture of metal atoms. I was taught that the strength of an alloy comes from the varying size of the different metals atoms, causes increased friction between the atoms, causing it to be harder for the atoms to slide against one another.

[Enthalpy]

As others have said, an alloy is just a mixture of metal atoms.

At least I didn't. I put "chemical bond".

I was taught that the strength of an alloy comes from the varying size of the different metals atoms, causes increased friction between the atoms, causing it to be harder for the atoms to slide against one another.

Among others... Cold-working hardens a metal too, without changing the atoms' size. And then you have all the precipitates stories, which go beyond individual atoms. Metallurgy is a bad mess.