1)What is the trend in boiling point of the fractions?
The volatile substances with lower boiling points rise to the top of column and the substances with higher boiling points are collected at the bottom. The boiling points are in ascending order from top to bottom in the column. In the test tube diagram above, the boiling point of the substances decreases from left to right. In general, the larger the molecule, the higher its boiling point.
2)Define viscosity.
Viscosity is a measure of the resistance of a fluid which is being deformed by shear or tensile stress.
Source: www.wikipedia.com
3) What is the trend in viscosity of the fractions?
In general, the larger the molecule, the higher the viscosity. As you know, large molecules have higher boiling points because there are more bonds to break. Therefore, the viscosity decreases as you go up the column. In the diagram above, the viscosity of the fractions decrease from left to right.
4)What is the trend in colour of the fractions?
The colour of the fractions become darker as you go up the column. In the diagram above, the colour gets darker from right to left. In general, the larger, more viscous the molecule, the darker its colour.
5)Why is crude oil separated into fractions?
Crude oil itself is a useless substance and therefore it is separated through fractional distillation to form other useful substances.
6)What process is used to separate crude oil into fractions?
Crude oil is separated by a process called fractional distillation in which the different boiling points of the unique substances allow it to be separated into fractions. The substances with the lowest boiling point at the top and the substance with the highest boiling point at the bottom.
7) What physical property allows this process to work?
It has different boiling points.
5.9 Q7 please don't use the word 'it' in your answers, it should be 'the fractions have different boiling points'
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