A-level生物真题解析 让我们从真题中获取考试经验
2017-12-06     00:00 来源: 来自互联网
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摘要:​下面给学习A-level辅导的学生们提供一些资料,希望能对大家的学习有所帮助。

A-level生物真题解析 让我们从真题中获取考试经验

下面给学习A-level辅导的学生们提供一些资料,希望能对大家的学习有所帮助:
Some foods contain ‘hydrogenated vegetable oils’. These are unsaturated fats that have been
converted to saturated fats.
Which property of the fats will have changed?
A Their hydrocarbon chains will fit together more closely.
B Their solubility in water will increase.
C They will have more double bonds in their molecules.
D They will remain liquid at room temperature.
题中说道,植物油为不饱和脂,转化为饱和脂类之后会发生怎么的性质变化。
生活中我们应该会看到花生油或大豆油都是液态的,因其不饱和;而猪油饱和程度大,所以常温下为固态。所以由不饱和脂转化为饱和脂状态应该由状态应该更接近于固态,所以D错,其固化程度高了,水溶性肯定不会提高,所以B错。而不饱和程度其实是由其不饱和键决定的(双键或三键),不饱和程度高,其双键应该多,所以C错。最终只能选A,因为饱和程度大意味着氢多了,所以链应该更近了。



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