Water & Water Pollution (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards
Exam code: 0654 & 0973
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Anhydrous copper(II) sulfate is ______ in colour. When water is added it turns ______, forming hydrated copper(II) sulfate.
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Cards in this collection (12)
Anhydrous copper(II) sulfate is ______ in colour. When water is added it turns ______, forming hydrated copper(II) sulfate.
Anhydrous copper(II) sulfate is white in colour. When water is added it turns blue, forming hydrated copper(II) sulfate.
True or False?
Anhydrous cobalt(II) chloride paper can be used to test for the presence of water.
True.
Anhydrous cobalt(II) chloride paper is blue. The presence of water turns it pink, confirming that water is present.
How do impurities affect the boiling point and melting point of water?
Impurities increase the boiling point of water above 100 °C and decrease the melting point below 0 °C.
Pure water boils at exactly 100 °C and melts at exactly 0 °C.
Distilled water is used in practical chemistry instead of tap water because it contains fewer ______ ______.
Distilled water is used in practical chemistry instead of tap water because it contains fewer chemical impurities.
What is the pH of pure water, and how can this be used to assess purity?
The pH of pure water is exactly 7. A pH that deviates from 7 indicates the presence of dissolved impurities that make the water acidic or alkaline.
Why does a horizontal line on a heating curve confirm that a water sample is pure?
A horizontal line shows the water melts or boils at a precise, fixed temperature. Pure water has a sharp melting point of 0 °C and a sharp boiling point of 100 °C, whereas impure water changes state over a range of temperatures.
What are the three main stages of treating domestic water supplies?
The three stages are:
Sedimentation and filtration to remove solids
Filtration through carbon (charcoal) to remove tastes and odours
Chlorination to kill microbes.
In water treatment, filtration through ______ removes unpleasant tastes and odours from the water.
In water treatment, filtration through carbon (charcoal) removes unpleasant tastes and odours from the water.
True or False?
Chlorination in water treatment removes bacteria and other microorganisms by filtering them out through sand and gravel.
False.
Chlorination kills microbes by adding chlorine to the water. Sand and gravel filtration removes solid particles, but microbes are too small to be trapped this way.
Why is sedimentation carried out before filtration in water treatment?
Sedimentation allows larger solid particles such as mud and sand to settle to the bottom of the tank under gravity. This removes most solids before the water passes through filters, making filtration more effective.
Chlorine is added to water supplies to ______ microbes. Diseases such as ______ and typhoid can arise from untreated water.
Chlorine is added to water supplies to kill microbes. Diseases such as cholera and typhoid can arise from untreated water.
What types of impurity does sedimentation and filtration through sand and gravel remove from water?
Sedimentation and filtration through sand and gravel remove insoluble solid impurities such as mud, sand and other particles. Soluble impurities and microbes are not removed by this stage.
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