Crystalization/soldification of particles in a mixture

[candy4me]

Hello,

As part of my science project I am looking for a way to solidify a copper/sand mixture (or copper with any of the other allotropes of silicon dioxide). Can you grind the copper into small pieces like the sand, and then crystallize the mixture to make a "chunk" of the sand/copper mixture? (Copper and sand both have high melting points, so I can't melt them and let them freeze again.)

Thank you!

[deleted-93346]

Welcome to the Forum.

I do not understand what you propose to do when you say "crystallize the mixture to make a "chunk" of the sand/copper mixture". How does one crystallize a solid mixture?

[candy4me]

So -- let's say you have a mixture of soil, which is made of clay and sand particles. Is there any way you can soldify the mixture so it becomes like a rock again? And, would a similar technique work with crushed copper and sand particles?

The reason I mentioned crystals is because when rock candy is made, the sugar particles form a crystal, and the texture of the sand and sugar is similar.

[deleted-76520]

Hello!

Unfortunately, usually rock-like materials require a great deal of time, pressure, and/or heat to form. (As you said, melting isn't really an option). You could try buying copper foil and compressing it with sand to make a solid-ish chunk, but that might not apply depending on what you're testing on the chunk.

Crystals are much easier to make, but the issue is that in order to make crystals, you would need to dissolve the mixture (like sugar in water) and then force it to re-crystallize. To dissolve a mixture of clay and sand or a mixture of copper and sand, you would need to find something that dissolves them, and then make them crystallize at the same time-- quite a difficult feat, and involving some nasty chemicals.

How solid would you need the mixture to be, and what would it be needed for? My first thought is to use some kind of material that won't affect your experiment to hold the mixture together, but that depends on your experiment.

[deleted-93346]

In all the mixtures you mentioned there are in fact a wide variety of molecules, each assembled into microscopic granules with varying molecular configurations, for example silicon dioxide (SiO2) can be configured as a crystal, as a glass, or in hydrated forms (bonded internally with water molecules) and each of these can be combined into materials with different microstructures that are large compared to the molecules of SiO2, but very small compared to, say, a grain of sand. Furthermore small amounts of other molecules are typically found in close association in these microstructures; these affect the color and other properties of the resulting substance. The result is a large variety of substances can be made from SiO2: large crystals of quartz, fine silica sand, clays, chalcedony in many colors, fused silica glass, and more. Combined with substances made from other molecules, a bewildering array of minerals results. So it is not simple to say how to "crystalize" a complex mixture of minerals (plus organic components!) like soil.

Putting chemistry and mineralogy aside, however, as a practical matter is is usually pretty easy to solidify soil if it has enough clay -- just get it moist, compress it into rectangular blocks about 2 inches thick, 6 inches wide, and 12 inches long (the exact dimensions don't matter much), then sun dry the blocks for several days (assuming you have hot, sunny weather). The result will be bricks of "adobe", which are solid enough to use for building structures like houses -- I used to live in one! (Actually for good quality adobe you need a lot of clay and sand in the soil and very little organic matter except for some straw that is added to prevent the block from cracking. Also wooden forms are used to mold the moist clay soil into neat rectangles that are all the same size. Look up "adobe" on Wikipedia for lots more information.) While adobe is quite solid it is not a crystal. However, if you took a bit of adobe, crushed it, and looked at the resulting powder with a suitable microscope, you would find many tiny grains, made mostly of crystals of quartz and related minerals.

This method of solidifying soil would not work for a mixture of copper and sand, but adding a small amount shredded copper foil to the adobe mixture might not prevent solidification of the adobe. Do NOT grind copper into fine fragments -- there is an extreme hazard of a fire that is so hot that it's very difficult to control, and if the fragments are small enough to float in air like dust, there could be an explosion.

[candy4me]

I have a question. Copper loses its outer electron to become stable, and thus has a positive charge, correct? So if SiO2 is a covalent bond (the atoms share electrons), then you could apply a negative charge (current) to pure silicon dioxide, and the copper atoms would be magentically attracted to the SiO2 molecules.

[deleted-93346]

"Copper loses its outer electron to become stable, and thus has a positive charge, correct?"
—No, atoms of copper in pure solid copper are uncharged.
—Also, in covalent bonds such as those in SiO2 neither atom loses/gains an electron, the atoms share electrons and no ions are formed.

“you could apply a negative charge (current) to pure silicon dioxide”
—Pure SiO2 does not conduct electricity; it is an excellent insulator.

“the copper atoms would be magentically attracted to the SiO2 molecules.”
— Neither copper or SiO2 are attracted to magnets, nor do they interact magnetically.
— Moving ions are deflected by magnetic fields, but they are not attracted to magnets like iron is.