Glossary H

Horse

Horses, mules, and oxen were the only means of moving heavy loads before steam and gasoline vehicles became available.   They were still used until the 1940s in agriculture, when tractors replaced them.   Each species had advantages over the other.   Horses were fastest and could deliver the most power.   It could be run until it dropped dead.   Mules had more stamina than horses, but could not be overworked without rebeling.   They were useful on canal towpaths because they feared water, so they were not apt to meander into the canal for a drink - unlike horses.   Oxen were the strongest of the 3 species, but they were slow.   They were more sure-footed, so they were valuable where the terrain was rough, such as in forests hauling lumber.   Unlike horses and mules, oxen would graze on prairie grass and sage, so they could forage for their own food during Great Plains treks by pioneers across the continent.

Horseshoe

Horseshoes are iron shoes nailed to the bottoms of horse hoofs.   They were used as early as 770 CE in south-central Asia.   They are essential to prevent injury to tender horse hoofs and they provide additional traction on soil.   The invention of horseshoes and horse collars increased the efficiency of the horse greatly.   Iron is a relatively cheap metal for horseshoes, first made by hand by blacksmiths, and later made by machine.

Hydrocarbon

A hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls. Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons. The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains. Coal and natural gas are also important sources of hydrocarbons.

Hydrocarbons are used mainly for fuels, such as heating oil, gasoline, propane because they release energy when burned.

Methane (gas) CH₄ + 2 O₂ + heat -> 2 H₂O + CO₂ + Energy

Propane (gas) C₃H₈ + 5O₂ + heat -> 3CO₂ + 4H₂O + Energy

Benzene (liquid): C₆H₆ + O₂ + heat -> CO₂ + H₂O + Energy

Paraffin (solid): C₂₀H₄₂ + oxygen + heat -> carbon dioxide + water + Energy