Sample Essay On Expansion And Contraction

When objects are heated, they expand, a phenomenon referred to as thermal expansion. Thermal expansion is exhibited in an object heated above absolute zero or -273 degrees Celsius. Thermal expansion is caused by increased atoms movements. Solids are made up of fixed atoms. When a solid is heated, the atoms gain kinetic energy and vibrate about their fixed position. Kinetic energy gained by molecules is proportional to heat energy gained. Hence expansion is directly proportional to heating temperatures. In fluids such as gases, the atoms are more sparsely packed and move haphazardly. Heating in gases causes the free atoms to move even faster hence expansion in fluids is very high compared to expansion in solids. This is a paper on the negative effects and the useful applications of thermal expansion.
Thermal expansion causes damage to structures such as pavements, tiled surfaces and bridges. During hot weather, overheating causes roads to crack, which encourages entry of moisture to the sub-grade levels of the pavement causing deterioration of its integrity. Tiled surfaces likely to be exposed to direct sunlight have to be designed with allowances for expansion. Heating causes tiles to get dislodged which ruins the tiled surface.
Thermal expansion is advantageous in several ways. Expansion of mercury in calibrated thermometer tubes enables the measurement of temperature. Also, different expansion rates between iron and brass are used in the design of a bimetallic strip. A bimetallic strip is a parallel combination of iron and brass bars riveted together. Strong cohesion bonds between iron atoms causes less expansion as compared to brass, which has weaker bonds between its atoms. A heated bimetallic strip bends towards the iron bar due to the lower expansion rate, which makes it shorter. Bimetallic strips are used in fire alarms and thermostats for temperature control.

Estimate how many atoms there are in a sheet of paper

Assume the diameter of an atom is 10-8 cm or 0.1 nm and the dimensions of an A4 paper are 21cm x 29.7cm x 0.01cm.

Assuming the A4 paper is a cube, the number of atoms that can fit in it are:

2110-8*29.710-8*0.0110-8=6.237*1024
An A4 paper contains 6.237x1024 Atoms.