Free Thermal Expansion Essay Sample

Solid and liquid substances expand when heated. This is due to the increased movement of atoms in a heated object. Heat increases the kinetic energy of atoms in a body. The kinetic energy causes atoms to vibrate vigorously about a fixed position in solids. In fluids, the atoms are not fixed and move haphazardly within the fluid. The increased kinetic energy causes the atoms of the fluid to move faster. Increased atom movement causes an increase in volume of substance. This is a paper on thermal expansion, its useful applications and itsnegative effects.
Thermal expansion has both advantages and disadvantages. Thermal expansion causes cracks in buildings and roads. Walls, especially long concrete perimeter fences develop cracks in hot weather due to expansion. Different expansion rates between pavement layers leads to buckling and cracking. Also, long bridges exhibit high thermal expansion, which necessitates the introduction of expansion allowances and rollers to accommodate for the increased length. Thermal expansion complicates designs of various mechanical structures and shortens their lifetimes.
Thermal expansion is applied when joining items such as pipes or bushes and shafts. Heating one item makes it expand and as such, both items of a joint can be easily slid into each other. Cooling causes shrinkage which gives a tight shrink fit. Thermal expansion is also applied in the design of bimetallic strips used as thermostats and fire sensors. Bimetallic strips, designed from the expansion rate difference between iron and brass, are used to actuate electrical circuits or operate mechanical switches.

Estimate how many atoms there are in a sheet of paper

The average A4 paper has a length of 29.7cm and a width of 21cm. The average paper thickness is 0.01cm. By considering the number of atom diameters which can fit into each of the given dimensions above, an estimate of the atoms in an A4 paper can be obtained. The average diameter of an atom is 10-8 cm
29.7/10-8 = 2.97x109 , 21/10-8 = 2.1x109, and 0.01/10-8 = 1.0x106 ,
The atoms per A4 paper are 2.97x 109 x 2.1 x 109 x 1.0 x 106 = 6.237x1024 atoms.