MENJADI GURU BERMUTU DAN PROFESIONAL
Hydrogen is the most common element in the universe and was perhaps the first to form. It is among the ten most common elements on Earth as well and one of the most useful for industrial purposes. Under normal conditions of temperature, hydrogen is a gas. Designated as H, hydrogen is the first element in the periodic table because it contains only one proton. Hydrogen can combine with a large number of other elements, forming more compounds than any of the others. Pure hydrogen seldom occurs naturally, but it exists in most organic compounds, that is, compounds that contain carbon, which account for a very large number of compounds. Moreover, hydrogen is found in inorganic compounds. For example, when hydrogen burns in the presence of oxygen, it forms water.
The lightest and simplest of the elements, hydrogen has several properties that make it valuable for many industries.
It releases more heat per unit of weight than any other fuel. In rocket engines, tons of hydrogen and oxygen are burned, and hydrogen is used with oxygen for welding torches that produce temperatures as high as 4,000 degrees F. and can be used in cutting steel. Fuel cells to
Generate electricity operate on hydrogen and oxygen.
Hydrogen also serves to prevent metals from tarnishing during heat treatments by removing the oxygen from them. Although it would be difficult to remove the oxygen by itself, hydrogen readily combines with oxygen to form water, which can be heated to steam and easily removed. Furthermore, hydrogen is one of the coolest refrigerants. It does not become a liquid until it reaches
Temperatures of -425 degrees F. Pure hydrogen gas is used in large electric generators to cool the coils.
Future uses of hydrogen include fuel for cars, boats, planes, and other forms of transportation that currently require petroleum products. These fuels would be lighter, a distinct advantage in the aerospace industry, and they would also be cleaner, thereby reducing pollution in the atmosphere.
Hydrogen is also useful in the food industry for a process known as hydrogenation. Products such as margarine and cooking oils are changed from liquids to semisolids by combining hydrogen with their molecules. Soap manufacturers also use hydrogen for this purpose. In addition, in the chemical industry, hydrogen is used to produce ammonia, gasoline, methyl alcohol, and many other
1. What is the author’s main purpose in the passage?
A. To explain the industrial uses of hydrogen
B. To describe the origin of hydrogen in the universe
C. To discuss the process of hydrogenation
D. To give examples of how hydrogen and oxygen
2. How can hydrogen be used to cut steel?
A. By cooling the steel to a very low temperature
B. By cooling the hydrogen with oxygen to a very low temperature
C. By heating the steel to a very high temperature
D. By heating the hydrogen with oxygen to a very high temperature
3. The word ‘readily’ in line 22 could be best be replaced by
4. The ‘combining’ in line 35 is closest in meaning to
5. The word ‘them’ in line 21 refers to
A. fuel cells
6. Where in the passage does the author explain why hydrogen is used as a refrigerant?
A. Lines 8-10
B. Lines 15-18
C. Lines 20-21
D. Lines 24-26
7. What does the author mean by the statement in lines 21-24: Although it ………………… easily removed’?
A. It is easy to form steam by heating water.
B. Water can be made by combining hydrogen and oxygen.
C. Hydrogen cannot be separated from oxygen because it is too difficult.
D. Oxygen is removed by combining it with hydrogen and heating it.
8. How does hydrogen generally occur?
A. It is freely available in nature.
B. It is contained in many compounds.
C. It is often found in pure form.
D. It is released during hydrogenation.
9. The author mentions all of the following as uses for hydrogen EXCEPT
A. to remove tarnish from metals
B. to produce fuels such as gasoline and methyl alcohol
C. to operate fuel cells that generate electricity
D. to change solid foods to liquids
10. It can be inferred from the passage that hydrogen
A. is too dangerous to be used for industrial purposes
B. has many purposes in a variety of industries
C. has limited industrial uses because of its dangerous properties
D. is used in many industries for basically the same purpose