It depends how the solid is bound together, although the differentiation is not "bulk" vs. "molecule" here. Bulk is always the part of a material that's not the surface, but that's both true for solid glucose and graphite.

What you want to differentiate here as basic types:

• solids like rock salt whose bonds are mostly ionic
• solids in which covalent bonds have a major part in the bonds, e.g. rubber
• solids comprising small molecules like glucose in which a lot of the binding energy comes from intermolecular forces

Now, in reality the binding of the atoms within the solid is a mixture of the three and it is not always clear in which category you should put something or whether hydrogen bonds are an intermolecular force or a weak multiple-center bond. It is debatable whether the last two should be considered two categories or two subcategories of one supercategory. Especially graphite is tricky in this respect: if it is crystalline as in HOPG, you have those large graphene sheets which are no longer molecules, but if you come to powder in which the sheets may become a lot smaller and can essentially be considered large PAHs so in that limit it would actually be on the verge of being a molecular solid.

Jürgen Weippert Thank you

Glucose powders and graphite powders are both considered bulk materials, but they are different in terms of their molecular structure.

A molecule is a group of atoms that are bonded together and function as a unit. Molecules can be composed of a single type of atom, such as oxygen (O2), or they can be composed of multiple types of atoms, such as water (H2O). Molecules are typically very small, with sizes ranging from a few nanometers to a few angstroms.

Bulk materials, on the other hand, are materials that are made up of a large number of molecules or atoms. Bulk materials can be either crystalline or amorphous, and they can have a variety of physical properties such as density, conductivity, and melting point.

The difference between molecules and bulk materials is essentially one of scale. Molecules are very small, individual units that make up a bulk material. The properties of a bulk material are determined by the properties of the individual molecules that make it up, as well as the way those molecules are arranged and interact with each other.

In the case of glucose powders and graphite powders, both are considered bulk materials because they are made up of a large number of individual molecules or atoms. However, they differ in terms of their molecular structure and the way the atoms are arranged. Glucose is a simple sugar made up of carbon, hydrogen, and oxygen atoms, while graphite is a form of carbon in which the atoms are arranged in a hexagonal lattice structure.