I
Any burrowing, often blind insectivore in the family Talpidae (including 42 species of true moles) or Chrysochloridae (18 species of golden moles).
Most species have short legs and tail, a pointed head, velvety grayish fur, no external ears, and a strong odour. They range from 3.5 to 8 in. (9 to 20 cm) long. The forelimbs are rotated outward like oars and have broad or pointed claws on the toes. Moles are active day and night, digging surface tunnels in search of earthworms, grubs, and other invertebrates and excavating deep (10 ft [3 m]), vented burrows (molehills) for occupancy. The star-nosed mole ( Condylura cristata ) of northeastern North America has 22 pink, tentacle-like touch organs radiating from its muzzle.
II
Pigmented flat or fleshy skin mark, made up mostly of cells that produce melanin , which gives moles their light to dark brown or black colour and, in the dermis, a bluish cast.
Thicker moles also contain nerve elements and connective tissue. Moles often begin in childhood, usually as flat spots between the dermis and epidermis. Those that remain there are more likely to become malignant. Most move into the dermis and become slightly raised. In children, moles may undergo changes resembling cancer but are benign. Malignant melanoma can begin in moles but almost never before puberty. During pregnancy, moles may enlarge and new ones may appear. Moles sometimes disappear with age. The term nevus refers to a congenital skin mark, whereas a mole may develop after birth. Epidermal nevi are usually the same colour as the surrounding skin.
III
or mol
Standard unit for measuring everyday quantities of such minute entities as molecule s.
For any substance, the number of atoms or molecules in a mole is Avogadro's number (6.02 × 10 23 ) of particles. Defined exactly, it is the amount of pure substance containing the same number of chemical units that there are in exactly 12 g of carbon -12. For each substance, a mole is its atomic weight , molecular weight , or formula weight in gram s. The number of moles of a solute in a litre of solution is its molarity ( M ); the number of moles of solute in 1,000 g of solvent is its molality ( m ). The two measures differ slightly and have different uses. See also stoichiometry .