The History and Composition of Laundry Detergent
The earliest ancient people used plain water for cleaning. Water can dissolve different kinds of substances and then rinse them away. However, substances like fat (grease) are not soluble in water, which is why it is necessary to add detergent (a cleaning agent) to water to remove certain types of stains from clothes. One of the earliest detergents used was natron. The ancient Egyptians harvested it from dry lake beds, where it had been formed from plants rich in sodium (a component of salt) that once grew in the lake water. Natron was effective because it contains soda ash (so named because it is also produced when sodium-rich plants are burned), and soda ash reacts with fat to form soap when the substances are heated. Soap’s solid form was probably discovered accidentally when fat dripped into a cooking fire over four thousand years ago and mixed with ashes from the fire. However, this kind of soap was primarily used to style hair until the second century c.E., when the Greek physician Galen recommended it for cleaning. Soap allows greasy substances to be washed away because the soap molecule is asymmetrical, with an uncharged part that clings to grease and a negatively charged part that attracts water, thus forming a bridge between water and grease.
Although soda ash is an ingredient of soap, additional soda ash is needed when soap is used in mineral-rich water. Minerals bind to soap, resulting in solid soap um that is difficult to remove from clothing. Furthermore, iron, which is one of the minerals often present in the water, can have the effect of turning laundry yellow. When used by itself (not as a component of soap), soda ash can remove minerals from the water, thereby “softening”mineral-rich (“hard”)water and preventing undesirable changes of color.
Production of soda ash from plant matter is time- consuming and natron deposits are rare. In the 1800s, Belgian chemist Ernest Solvay developed an economical method for making soda ash from limestone, a type of rock that is rich in calcium. He used salt water to dissolve and remove the calcium in limestone and replace it with the sodium from salt water. Solvay’s approach tremendously expanded soap manufacturing, leading to a shortage of soap’s other major component, fat. This shortage deepened during the First World War, forcing the development of petroleum-based detergents, which act similarly to soap. Petroleum-based detergents work better in hard water than soap does and are now the most common type of detergent.
Grease is not the only substance that is difficult to remove from clothes and, therefore, soap is often inadequate. In 1913, German pharmacist Otto Rohm patented a formula containing pancreatic enzymes, which he initially used for tanning (turning animal skins into leather), as a laundry soak solution. These enzymes are normally released from the pancreatic gland of mammals into the small intestine, where they break down large biological molecules into smaller ones that can be absorbed into the bloodstream. Rohm realized these enzymes could be used to remove stains, which are often biological in origin, from clothing. In the 1960s, digestive enzymes began being extracted from bacteria, which proved cheaper than Rohm’s method. Bacterial enzymes also eliminate the need to presoak laundry and enable detergents to remove stains at a lower water temperature. One bacterial enzyme, cellulase, breaks down the cellulose fibers from which some fabrics are made. However, added in very small quantities it clips off loose fabric ends that result from wear, giving the fabric a smooth, bright appearance and soft feel.
Some stains in white fabric are so persistent that they need to be masked through bleaching. Bleaches change colored molecules, such as the red molecules found in cherry juice, into colorless ones. So does sunlight, and before the existence of chemical bleaches people used to bleach clothes by laying them in the sun. Discovered in the early twentieth century, optical brighteners are organic chemicals that are added to detergents without dyes. These compounds change invisible ultraviolet light and reemit a portion of it as blue light, thus making laundry look clean and bright.
1
The earliest ancient people used plain water for cleaning. Water can dissolve different kinds of substances and then rinse them away. However, substances like fat (grease) are not soluble in water, which is why it is necessary to add detergent (a cleaning agent) to water to remove certain types of stains from clothes. One of the earliest detergents used was natron. The ancient Egyptians harvested it from dry lake beds, where it had been formed from plants rich in sodium (a component of salt) that once grew in the lake water. Natron was effective because it contains soda ash (so named because it is also produced when sodium-rich plants are burned), and soda ash reacts with fat to form soap when the substances are heated. Soap’s solid form was probably discovered accidentally when fat dripped into a cooking fire over four thousand years ago and mixed with ashes from the fire. However, this kind of soap was primarily used to style hair until the second century c.E., when the Greek physician Galen recommended it for cleaning. Soap allows greasy substances to be washed away because the soap molecule is asymmetrical, with an uncharged part that clings to grease and a negatively charged part that attracts water, thus forming a bridge between water and grease.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
Sentence Simplification Questions句子简化题
ABecause the soap molecule is asymmetrical, it has both an uncharged part and a negatively charged part.
BSoap molecules join water and grease molecules together, allowing greasy substances to be washed away.
CSoap forms a bridge between water and grease, which can make it difficult for soap to be washed away.
DWater and grease cling to each other because grease is uncharged and water is negatively charged.
2
The earliest ancient people used plain water for cleaning. Water can dissolve different kinds of substances and then rinse them away. However, substances like fat (grease) are not soluble in water, which is why it is necessary to add detergent (a cleaning agent) to water to remove certain types of stains from clothes. One of the earliest detergents used was natron. The ancient Egyptians harvested it from dry lake beds, where it had been formed from plants rich in sodium (a component of salt) that once grew in the lake water. Natron was effective because it contains soda ash (so named because it is also produced when sodium-rich plants are burned), and soda ash reacts with fat to form soap when the substances are heated. Soap’s solid form was probably discovered accidentally when fat dripped into a cooking fire over four thousand years ago and mixed with ashes from the fire. However, this kind of soap was primarily used to style hair until the second century c.E., when the Greek physician Galen recommended it for cleaning. Soap allows greasy substances to be washed away because the soap molecule is asymmetrical, with an uncharged part that clings to grease and a negatively charged part that attracts water, thus forming a bridge between water and grease.
According to paragraph 1, which of the following is true of natron?
Factual Information Questions事实信息题
AIt is produced when sodium-rich plants are burned.
BIt may have been discovered accidentally when fat dripped into a fire.
CIt dissolves some substances, but not grease or fat.
DIt forms naturally from plants that grow in lakes
3
Production of soda ash from plant matter is time- consuming and natron deposits are rare. In the 1800s, Belgian chemist Ernest Solvay developed an economical method for making soda ash from limestone, a type of rock that is rich in calcium. He used salt water to dissolve and remove the calcium in limestone and replace it with the sodium from salt water. Solvay’s approach tremendously expanded soap manufacturing, leading to a shortage of soap’s other major component, fat. This shortage deepened during the First World War, forcing the development of petroleum-based detergents, which act similarly to soap. Petroleum-based detergents work better in hard water than soap does and are now the most common type of detergent.
The word “tremendously” in the passage is closest in meaning to
Vocabulary Questions词汇题
Asteadily
Bsuddenly
Cenormously
Dunexpectedly
4
Production of soda ash from plant matter is time- consuming and natron deposits are rare. In the 1800s, Belgian chemist Ernest Solvay developed an economical method for making soda ash from limestone, a type of rock that is rich in calcium. He used salt water to dissolve and remove the calcium in limestone and replace it with the sodium from salt water. Solvay’s approach tremendously expanded soap manufacturing, leading to a shortage of soap’s other major component, fat. This shortage deepened during the First World War, forcing the development of petroleum-based detergents, which act similarly to soap. Petroleum-based detergents work better in hard water than soap does and are now the most common type of detergent.
According to paragraph 3, which of the following did Solvay’s method of making soda ash involve?
Factual Information Questions事实信息题
ACombining limestone with salt water
BMixing calcium with fat
CUsing plant matter to remove calcium from a type of rock
DUsing petroleum to separate salt from limestone
5
Grease is not the only substance that is difficult to remove from clothes and, therefore, soap is often inadequate. In 1913, German pharmacist Otto Rohm patented a formula containing pancreatic enzymes, which he initially used for tanning (turning animal skins into leather), as a laundry soak solution. These enzymes are normally released from the pancreatic gland of mammals into the small intestine, where they break down large biological molecules into smaller ones that can be absorbed into the bloodstream. Rohm realized these enzymes could be used to remove stains, which are often biological in origin, from clothing. In the 1960s, digestive enzymes began being extracted from bacteria, which proved cheaper than Rohm’s method. Bacterial enzymes also eliminate the need to presoak laundry and enable detergents to remove stains at a lower water temperature. One bacterial enzyme, cellulase, breaks down the cellulose fibers from which some fabrics are made. However, added in very small quantities it clips off loose fabric ends that result from wear, giving the fabric a smooth, bright appearance and soft feel.
The word “inadequate” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aundependable
Bimpractical
Cunnecessary
Dinsufficient
6
Grease is not the only substance that is difficult to remove from clothes and, therefore, soap is often inadequate. In 1913, German pharmacist Otto Rohm patented a formula containing pancreatic enzymes, which he initially used for tanning (turning animal skins into leather), as a laundry soak solution. These enzymes are normally released from the pancreatic gland of mammals into the small intestine, where they break down large biological molecules into smaller ones that can be absorbed into the bloodstream. Rohm realized these enzymes could be used to remove stains, which are often biological in origin, from clothing. In the 1960s, digestive enzymes began being extracted from bacteria, which proved cheaper than Rohm’s method. Bacterial enzymes also eliminate the need to presoak laundry and enable detergents to remove stains at a lower water temperature. One bacterial enzyme, cellulase, breaks down the cellulose fibers from which some fabrics are made. However, added in very small quantities it clips off loose fabric ends that result from wear, giving the fabric a smooth, bright appearance and soft feel.
In paragraph 4, why does the author mention that stains on clothes are often biological in origin?
Rhetorical Purpose Questions修辞目的题
ATo help explain why digestive enzymes are effective at treating stains
BTo support the claim that many substances other than grease are difficult to remove from clothes
CTo illustrate the similarities between tanning animal skins and cleaning fabrics
DTo provide evidence that breaking down biological molecules makes them more easily absorbed
7
Grease is not the only substance that is difficult to remove from clothes and, therefore, soap is often inadequate. In 1913, German pharmacist Otto Rohm patented a formula containing pancreatic enzymes, which he initially used for tanning (turning animal skins into leather), as a laundry soak solution. These enzymes are normally released from the pancreatic gland of mammals into the small intestine, where they break down large biological molecules into smaller ones that can be absorbed into the bloodstream. Rohm realized these enzymes could be used to remove stains, which are often biological in origin, from clothing. In the 1960s, digestive enzymes began being extracted from bacteria, which proved cheaper than Rohm’s method. Bacterial enzymes also eliminate the need to presoak laundry and enable detergents to remove stains at a lower water temperature. One bacterial enzyme, cellulase, breaks down the cellulose fibers from which some fabrics are made. However, added in very small quantities it clips off loose fabric ends that result from wear, giving the fabric a smooth, bright appearance and soft feel.
Which of the following does paragraph 4 suggest would happen if too much cellulase were added to laundry detergent?
Factual Information Questions事实信息题
AThe cellulase would prevent other enzymes from effectively removing stains
BThe cellulase would damage cellulose fabrics.
CThe detergent would become ineffective at low water temperatures.
DThe detergent would make the fabric appear dull and feel rough
8
Some stains in white fabric are so persistent that they need to be masked through bleaching. Bleaches change colored molecules, such as the red molecules found in cherry juice, into colorless ones. So does sunlight, and before the existence of chemical bleaches people used to bleach clothes by laying them in the sun. Discovered in the early twentieth century, optical brighteners are organic chemicals that are added to detergents without dyes. These compounds change invisible ultraviolet light and reemit a portion of it as blue light, thus making laundry look clean and bright.
According to paragraph 5, which of the following is true of sunlight?
Factual Information Questions事实信息题
AIt is more effective in removing stains than bleaches are
BIt can make molecules lose their color.
CIt is the earliest known optical brightener.
DIts blue light is more completely absorbed by laundry than its ultraviolet light is.
9
Production of soda ash from plant matter is time- consuming and natron deposits are rare. [■] In the 1800s, Belgian chemist Ernest Solvay developed an economical method for making soda ash from limestone, a type of rock that is rich in calcium. [■] He used salt water to dissolve and remove the calcium in limestone and replace it with the sodium from salt water. [■] Solvay’s approach tremendously expanded soap manufacturing, leading to a shortage of soap’s other major component, fat. This shortage deepened during the First World War, forcing the development of petroleum-based detergents, which act similarly to soap. [■] Petroleum-based detergents work better in hard water than soap does and are now the most common type of detergent.
Look at the four squaresthat indicate where the following sentence could be added to the passage
As a result, for a long time soap remained too expensive for most people.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Although plain water can remove some substances from clothing, more advanced cleaning methods are often needed.
Prose Summary Questions概要小结题
Select 3 answers
ANatron, used by the ancient Egyptians, was one of the first cleaning agents, while soap began to be used for cleaning after a Greek physician recommended it for the purpose
BA newly developed method to make soda ash from limestone increased soap production in the 1800s, but petroleum-based detergents largely replaced soap after the First World War
CThe first fabric softener was based on a formula that was commonly used for tanning leather, which was discovered to give fabrics a smooth, bright appearance and soft feel
DBefore the nineteenth century, soda ash was often used without other components, because the soap manufactured then was effective only when it reacted with minerals in hard water
EIn the early twentieth century, a German pharmacist developed a detergent containing bacterial enzymes, but these were only effective at very low temperatures
FDevelopments in the 1900s included the introduction of detergents with digestive enzymes to remove stains and optical brighteners to make laundry appear cleaner.
答案：
