Harmful Effects of Non-metals and Their Compounds PDF

## Harmful effects of non-metals and their compounds ### Non-metals #### Table 20.4.6 The uses of silicon and its compounds | Non-metal/compound | Uses | |---|---| | Silicon | - in the manufacture of silicon chips used in electronic devices from pocket calculators to computers - to make silicon...

## Harmful effects of non-metals and their compounds ### Non-metals #### Table 20.4.6 The uses of silicon and its compounds | Non-metal/compound | Uses | |---|---| | Silicon | - in the manufacture of silicon chips used in electronic devices from pocket calculators to computers - to make silicone implants for plastic and reconstructive surgery - to make a silicon steel alloy in the steel industry | | Silicon dioxide (quartz) (SiO2) | - in jewellery, e.g. amethyst is purple quartz - in the manufacture of glass - silicon dioxide is the main ingredient of glass - in the manufacture of cement | | Metal silicates | mixed with cement and aggregate to make concrete to make ceramic products, such as pottery and porcelain products, roof tiles, floor tiles, building bricks and sewer pipes | ### Summary questions 1. Which four compounds of non-metals are used to make fertilisers? 2. What is mean by 'vulcanisation of rubber'? Name the non-metal that is used to vulcanise rubber and explain what happens during the process of vulcanisation. 3. Discuss some of the uses of the following non-metals and their compounds: - carbon - chlorine - silicon ### Objectives By the end of this topic you will be able to: - discuss the harmful effects of non-metals and their compounds on living systems and the environment. ### C20.5 Harmful effects of non-metals and their compounds While non-metals and their compounds are extremely useful to humans, some compounds of the same non-metals can have harmful effects on living systems and the environment. Like certain metals, the concentrations of these non-metal compounds within the environment are increasing due to pollution caused by man's activities. These harmful substances are called **pollutants**. We will now look at some of the sources of some of these pollutants and their negative effects on the environment in Table 20.5.1. Some of these effects will also be discussed in more detail after the table. ### Table 20.5.1 Harmful effects of some compounds of non-metals | Non-metal compound/ pollutant | Sources in the environment | Harmful effects | |---|---|---| | Sulfur dioxide (SO₂) | Combustion of fossil fuels, especially coal and heavy oils, e.g. in industry and power stations | Sulfur dioxide causes respiratory problems in humans, e.g. bronchitis. It reduces the growth of plants and dissolves in rainwater forming an acidic solution known as **acid rain** (see later in this unit). | | Carbon monoxide (CO) | Incomplete combustion of fossil fuels, mainly in motor vehicles | Carbon monoxide binds with haemoglobin much more readily than oxygen causing a reduction in the amount of oxygen reaching body tissues. This reduces respiration and mental awareness, causes visual impairment, dizziness, headaches, unconsciousness and even death. | | Carbon dioxide (CO2) | Complete combustion of fossil fuels, e.g. in motor vehicles, industry, power stations and aeroplanes | Carbon dioxide, together with other gases, builds up in the upper atmosphere contributing to the **greenhouse effect** and **global warming** (see later in this unit). About 25% of the carbon dioxide released is absorbed by the oceans leading to **ocean acidification**. This increase in acidity is expected to affect the ability of shellfish such as oysters, sea urchins and corals to produce and maintain their shells. | | Hydrogen sulfide (H2S) | Decay of organic matter in garbage dumps, landfills and farmyards. Released from petroleum refineries. | Hydrogen sulfide is extremely toxic. Like carbon monoxide, it combines readily with haemoglobin, which reduces cellular respiration and causes dizziness, headaches, unconsciousness and even death. Low concentrations irritate the eyes and respiratory system.| | Oxides of nitrogen (NO and NO₂) | Combustion at high temperatures in motor vehicle engines and power stations causing nitrogen and oxygen in the air to react | Oxides of nitrogen are extremely toxic causing lung damage. Low concentrations irritate the skin, eyes and respiratory system. They also cause leaves to die, reduce the growth of plants, play a major role in the development of **photochemical smog** and dissolve in rainwater forming acid rain (see later in this unit).| | Chlorofluorocarbons (CFCs) | Used as a refrigerant in air-conditioners and refrigerators and as a propellant in some aerosol sprays | CFCs break down the **ozone layer** in the upper atmosphere allowing more ultraviolet light to reach the Earth's surface (see later in this unit). | | Carbon particles (C) | Combustion of fossil fuels, e.g. in industry. Bush fires and cigarettes. | Carbon particles blacken trees reducing photosynthesis and blacken buildings. They combine with water vapour and sulfur dioxide to form **smog**, which causes poor visibility for drivers and aircraft pilots and respiratory problems, e.g. bronchitis, asthma and lung disease. | | Nitrate ions (NO3-) and phosphate ions (PO43-) | Fertilisers used in agriculture, especially in intensive farming. Synthetic detergents. | These ions cause **eutrophication** (see later in this unit) | Pesticides, e.g. insecticides, fungicides and herbicides | Used in agriculture for pest control, disease control and control of weeds. Used to control vectors of disease, e.g. mosquitoes | Pesticides concentrate up food chains harming top consumers (see later in this unit). They can also harm useful as well as harmful organisms, for example, bees which are essential for pollination are being killed by insecticides. | ### Acid rain Acid rain is formed when pollutant gases such as sulfur dioxide and oxides of nitrogen are released into the atmosphere. These oxides are acidic and when they react with rainwater they form acidic solutions, for example: - SO2(g) + H2O(l) → H2SO3(aq) *sulfurous acid* - 2NO2(g) + H2O(l) → HNO2(aq) + HNO3(aq) *nitrous acid* *nitric acid* These acidic solutions then fall to Earth as **acid rain** which can have a serious effect on plants, animals, the soil and water. Acid rain decreases the pH of the soil, damages crops, trees and other plants and harms animals. It also corrodes buildings, cars, machinery and historical monuments and it causes lakes, streams and rivers to become acidic and unsuitable for aquatic organisms, such as fish. ### Figure 20.5.2 A limestone statue corroded by acid rain