10 1 water and water pollution

Anhydrous copper(II) sulfate turns blue in the presence of water.

Anhydrous cobalt(II) chloride turns pink in the presence of water.

A pure substance consists of a single element or compound.

The physical test to determine whether a sample of water is pure is to check its boiling point which should be exactly 100 oC.

True. Impurities tend to raise the boiling point of water.

The piece of apparatus used to check the boiling point of water is a thermometer.

False. Impurities tend to lower the melting point of water.

Distilled water is used in practical chemistry because of its high purity, which prevents interference with chemical reactions.

Four substances found in water from natural sources could include:

Two beneficial substances found in water from natural sources are dissolved oxygen and some metal compounds.

Dissolved oxygen is beneficial in water because it is essential for aquatic life.

Two potentially harmful substances found in water from natural sources are sewage and some metal compounds.

Nitrates and phosphates in water are often sourced from fertilizers, with phosphates also coming from detergents.

False. Not all metal compounds in water are harmful.

Eutrophication is a process where excess nutrients in water promote plant growth, leading to deoxygenation and damage to aquatic life.

The first step in the purification of water is filtration to remove large particles.

False. Distillation is not used in water purification.

Sedimentation allows heavy particles to settle at the bottom of the water treatment tanks.

Chlorination is the process of adding chlorine to water to disinfect it by killing bacteria and other pathogens.

False. Filtration removes large particles but not dissolved impurities.

False. Bacteria are too small to be trapped by filters, which is why chlorination is necessary.

Untreated water contains both soluble and insoluble impurities.

Examples of soluble impurities in water include dissolved calcium, metallic compounds, and inorganic pollutants.

The three main steps of water treatment are sedimentation/filtration, filtration/treatment with carbon, and chlorination.

Carbon (charcoal) is used in water treatment to remove unpleasant tastes and odours.

In fertilisers, NPK stands for nitrogen, phosphorus, and potassium.

Nitrogen in plant growth makes chlorophyll and protein, and promotes healthy leaves.

Potassium benefits plants by promoting growth and healthy fruit and flowers.

The main benefit of phosphorus for plants is promoting healthy roots.

Two common ions that are sources of soluble nitrogen in fertilisers are ammonium ions (NH4+) and nitrate ions (NO3-).

Phosphate ions (PO43-) are a source of soluble phosphorus in fertilisers.

False. Most common potassium compounds used in fertilisers dissolve in water to produce potassium ions (K+).

Three examples of common fertiliser compounds are ammonium nitrate (NH4NO3), ammonium phosphate ((NH4)3PO4), and potassium nitrate (KNO3).

False. Different fertilisers contain different proportions of nitrogen, potassium, and phosphorus.