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The phosphorus cycle

Phosphorus is a chemical element found on Earth in numerous compound forms, such as the phosphate ion (PO43-), located in water, soil and sediments. The quantities of phosphorus in soil are ...

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The nitrogen cycle

Nitrogen is the most abundant element in our planet’s atmosphere. Approximately 78% of the atmosphere is made up of nitrogen gas (N2). Nitrogen is a crucially important component for all life. It ...

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What is fire?

Fire is the visible effect of the process of combustion – a special type of chemical reaction. It occurs between oxygen in the air and some sort of fuel. The products from the chemical reaction ...

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Positive and negative effects of UV

The Earth’s atmosphere blocks most of the Sun’s UV radiation from penetrating through the atmosphere. The small amount that gets through has both positive and negative effects. Positive ...

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Measuring biodegradability

In nature, different materials biodegrade at different rates. If you throw your apple core into the bushes along with a steel toy car, your apple core will have disappeared in a few months and ...

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States of matter

Anything that has mass is made up of matter – an all-encompassing word for atoms and molecules that make up our physical world. We describe this matter as existing in states (sometimes referred ...

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Cleaning up the oil spill

On 5 October 2011, the cargo vessel Rena ran aground on the Astrolabe Reef. The ship was carrying 1700 tonnes of heavy fuel oil and about 200 tonnes of diesel in its tanks. Over 360 tonnes of ...

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Soil properties

All soils contain mineral particles, organic matter, water and air. The combinations of these determine the soil’s properties – its texture, structure, porosity, chemistry and colour. Soil ...

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Uses for UV

There are a variety of ways we put ultraviolet (UV) radiation to good use. Our skin and UV When we expose our skin to UVB, it stimulates the production of vitamin D, which our bodies need. Window ...

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Enzymes in washing powders

Television commercials for washing powder often promote the "boosting power" of enzymes. Why are enzymes added to washing powder, and how do they work? Carry out some simple experiments to ...

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What are ceramics?

A ceramic is an inorganic non-metallic solid made up of either metal or non-metal compounds that have been shaped and then hardened by heating to high temperatures. In general, they are hard ...

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What is smoke?

What is smoke and why do some fires seem to have more smoke than others? Smoke is a collection of tiny solid, liquid and gas particles. Although smoke can contain hundreds of different chemicals ...

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Melting and freezing

Water can exist as a solid (ice), liquid (water) or gas (vapour or gas). Adding heat can cause ice (a solid) to melt to form water (a liquid). Removing heat causes water (a liquid) to freeze to ...

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Digestion – breaking the large into the small

Digestion of food involves both physical and chemical processes. Through digestion, large food particles are converted into smaller components that can be readily absorbed into the bloodstream. ...

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Carbonate chemistry

Calcium carbonate is the principal mineral component of limestone. Its chemical and physical properties lie behind the modern-day uses of limestone as well as the unique limestone landscapes of ...

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The human digestive system

The human digestive system consists of a long muscular tube and several accessory organs such as the salivary glandspancreas and gall bladder. It is responsible for food ingestion and digestion ...

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Earth system

Trying to understand how this planet we call home works can seem confusing – there are so many things going on at once! Scientists break down the way the Earth system works to a number of ...

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Fire behaviour

Fires behave differently. Some burn slowly and evenly; others are extremely hot, burning fiercely and quickly. Different fires have different coloured flames. Some fires start easily; others ...

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Chemical reactions and catalysts

A chemical reaction involves a chemical change, which happens when two or more particles (which can be molecules, atoms or ions) interact. For example, when iron and oxygen react, they change to ...

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Bioindicators

A bioindicator is a living organism that gives us an idea of the health of an ecosystem. Some organisms are very sensitive to pollution in their environment, so if pollutants are present, the ...

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Non-renewable energy sources

Energy comes from many sources, and to describe these sources we use two terms: renewable and non-renewable. Non-renewable energy resources cannot be replaced – once they are used up, they will ...

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Rate of digestion

Digestion of food involves chemical reactions that break up large food molecules into their ‘building block’ components. There are a number of factors that affect the rates of these reactions ...

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