20 Impact of Metals on Living ….

Corrosion of metals

Takes place when the surface of a metal is gradually worn away by reacting with chemicals in the environment (mainly oxygen and water vapor)

What can speed up corrosion

Certain pollutants

What happens to a metal when it corrodes

It it oxidized, to form the metal oxide

Salts may also form

Which metals corrode faster

The higher a metal is in the reactivity series, the faster it corrodes

The corrosion of aluminum

• beneficial

• When a fresh piece of aluminum is exposed to air it immediately forms a layer of aluminum oxide which adheres to the metal surface and does not flake off and is relatively unreactive, and therefore protects the metal form further corrosion

• Thickness of this layer can be increased by anodizing

The corrosion of iron

• detrimental

• Aka rusting

• When iron and steel objects are exposed to oxygen and moisture they immediately begin to corrode, forming mainly hydrated iron (III) oxide aka RUST

• Rust does not adhere to the iron and flakes off, exposing more iron to oxygen and moisture when much then rusts and this continues until the iron is gradually worn away

What are the macrominerals needed in humans

• calcium

• Potassium

• Sodium

• Magnesium

• Etc

What are the microminerals (trace minerals) needed in humans

• iron

• Zinc

• Manganese

• Cobalt

• Copper

• Molybdenum

• Selenium

• Chromium

How is magnesium important in living organisms

• it’s essential for plants to produce the green pigment, chlorophyll, found in the chloroplasts

• Chlorophyll is needed to absorb sunlight energy so plants can manufacture their own food through photosynthesis

What happens if there is a shortage of magnesium in plants

• chlorosis: where the leaves of the plants become yellow

Why do humans need magnesium

Many biochemical reactions in the human body need magnesium ions since they help many enzymes to function

Why is iron important in animals

• Essential for the production of haemoglobin, found in red blood cells

• Haemoglobin carries oxygen around the body for cells to use in respiration for energy production

What happens if there is a shortage of iron in animals

Anemia: number of red blood class is reduced causing tiredness and lack of energy

Whay is calcium needed in animals

• To produce calcium hydroxyapatite in the bones and teeth of animals

What can a shortage of calcium lead to?

Rickets in children: legs become bowed

Osteoporosis in adults: bones become weak and brittle

Why is zinc important in living organisms

For the functioning of the immune system, for wounds to heal and for growth and repair of cells and tissues

Why are sodium and potassium important

For impulses to be transmitted along nerves and for muscles to contract

What are hemoglobin and chlorophyll known as

Organometallic compounds bc they are organic compounds whose molecules contain metal ions

Heavy metal ions

Ions of certain transition metals and metalloids

They are toxins to living organisms especially when they are combined with organic compounds (forming organometallic compounds)

Occur naturally however pollution causes their concentration to increase

They are persistent meaning they remain in the environment for a long time

There also become higher in concentration she move up the food chains and can reach harmful levels in top consumers

Pollution

The contamination of the natural environment by the release of unpleasant and harmful substances into the environment

the major source of mercury in humans

Large fish like sharks, marlin and tuna

Harmful effects of lead in the environment

• damages various body tissues and organs like the kidneys, liver, bones, and nervous system, particularly the brain

• Interferes with the normal function of red blood cells which can lead to anemia

• Reduces iq in young children and causes behavioral problems and learning disorders

Sources of lead in the environment

Mining of lead ores,

Discarded lead-acid batteries

Lead-based paints

Car exhaust fumes when using leaded petrol in some countries

Harmful effects of arsenic

• causes changes in pigmentation and thickening of the skin - can cause cancer

• Damages the nervous system, heart, lungs and blood vessels

Sources of arsenic in the environment

Volcanic eruptions

Mining of certain metals, mainly gold

Burning of fossil fuels, especially coal

Harmful effects of cadmium

• damages the kidneys, liver and respiratory system if inhaled

• Can cause bones to become weakened and fragile, leading to osteoporosis

Sources of cadmium in the environment

Cigarette smoke

Discarded nickel-cadmium batteries

Burning fossil fuels

Incinerating waste

Harmful effects of mercury

• damaged the CNS (central nervous system) resulting in the loss of muscular co-ordination, numbness in hands and feet, impaired hearing, sight and speech: A condition known as minamata disease

Sources of mercury

Discarded fluorescent light bulbs

Discarded mercury thermometers from labs and hospitals

Burning coal in coal- fired power plants

Disposal of solid waste containing heavy metals

Should not be disposed in landfills since groundwater and nearby soil can be contaminated

Shluld not be incinerated because harmful gases containing their metal ions could be released into the air

They should be recycled

Examples of solid waste containing heavy metal

Lead-acid batteries

Nickel-cadmium batteries

Fluorescent light bulbs

Hospital and laboratory thermometers