خليط الفصل قطعة قراءة ستيب رقم 80
قطعة 80 من 99 في تدريب القراءة المجاني لاختبار الستيب (STEP)، عليها 4 أسئلة اختيار من متعدد. اقرأ القطعة وجاوب، ثم اضغط «اعرض الإجابة» تحت كل سؤال عشان تتأكد.
نص القطعة
It is important to be able to separate mixtures to obtain a desired component from the mixture and to be able to better understand how each component contributes to the properties, chemical and physical, of the resulting mixture. Most of the chemical reactions in real life occur in mixtures, but purifying a mixture into its components allows scientists to study how each part behaves and to make improvements to the reactions. Here are a number of common separation techniques: Filtration: The filtration process is generally used to separate a suspension mixture where small solid particles are suspended in liquid or air. In the case of filtering water, the water is forced through a paper that is made up of a very fine mesh of fibers. The water that has been run through the filter is called the filtrate. The particles that are removed from the water by the filter are called the residue. For example, muddy water is poured through a funnel lined with filter paper to remove the small sand and clay particles. So, filters work best when they prevent solids from going through them. Centrifuge: In some cases, there are suspension mixtures where the solid particles are too fine to be separated with a filter. In these cases, sometimes a centrifuge is used. Centrifuges are mechanical devices that spin at very high speeds. These high speeds allow the solid particles in suspensions to settle (sink to the bottom) very quickly. The liquid parts split off and can be decanted. For example, rather than wait for sand to slowly settle to the bottom of water, a centrifuge can cause the sand to settle in a matter of seconds. Some examples of how centrifuges are used include separating blood into plasma and red cells, separating cream from milk, and separating uranium isotopes for nuclear power plants.
أسئلة القطعة (4)
What does the writer think about the process of separating mixtures?
- A. He thinks it's a new technique that needs to be developed.
- B. He thinks it's an ancient process that is useful in cooking.
- C. He thinks it's important because it helps to take out the substances that have benefits.
- D. He thinks it's important because it keeps impurities from creating new diseases.
اعرض الإجابة
C. He thinks it's important because it helps to take out the substances that have benefits.
Which words can we use to replace the words "for example" in Paragraph (2)?
- A. of course
- B. above all
- C. for instance
- D. at the same time
اعرض الإجابة
C. for instance
What does Paragraph (2) say about filtering?
- A. It is usually used in making coffee.
- B. It only works if the filter paper has a special number of holes.
- C. It is a process that only works when separating sand from a mixture.
- D. It works best when the filter paper is able to stop the solid from passing.
اعرض الإجابة
D. It works best when the filter paper is able to stop the solid from passing.
How does centrifuging solve the problem of separating very small solids from a liquid?
- A. It moves the liquid around very quickly to get the solids to stay at the bottom.
- B. It uses a special heating technique that is only available in some laboratories.
- C. It uses boiling to separate an insoluble solid from a liquid.
- D. It uses a filter to separate solids, like sand, from a liquid.
اعرض الإجابة
A. It moves the liquid around very quickly to get the solids to stay at the bottom.