1. Suggest how copper sulfate can be used as a test for the presence of water - AQA - GCSE Chemistry Combined Science - Question 3 - 2021 - Paper 2

A pure substance is defined as a single element or compound that is not mixed with any other substance, consisting entirely of one type of particle.

The boiling point of the sample is 100.60 °C, which is an increase of 0.60 °C from the boiling point of pure water. Each 1% impurity increases the boiling point by 0.12 °C.

To find the percentage of impurity: ext{Percentage of impurity} = rac{0.60 °C}{0.12 °C} = 5

Now calculating the mass of the impurity: ext{Mass of impurity} = rac{5}{100} imes 250 ext{g} = 12.5 ext{g}

To obtain potable water from salty water, the salty water is heated until it evaporates, transforming into water vapor. The water vapor is then cooled and condensed back into liquid form, effectively separating the salt from the water in a process known as distillation.

Obtaining potable water from salty water is more expensive because it requires distillation, which consumes energy to boil the water. In contrast, obtaining potable water from ground water typically involves simpler processes such as filtration and sterilization, which are less energy-intensive.