Is the smallest chemical unit of a type of pure substance.

The smallest part of an element which is characterised by sharing the chemical properties of an element. or has a property of a chemical element is said to be an atom.

An atom consist of nucleus which is surrounded by electrons i.e. negatively charged particle. Atoms also contains protons i.e. positively charged particle and neutrons i.e. neutral particle. The atomic size depends upon the number of protons, number of neutrons as well on number of electrons.

Hence, atom is the smallest chemical unit of a type of pure substance.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.