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ARTICLE

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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ARTICLE

How elements are formed

Our world is made of elements and combinations of elements called compounds. An element is a pure substance made of atoms that are all of the same type. At present, 116 elements are known, and ...

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ARTICLE

Heat energy

Most of us use the word ‘heat’ to mean something that feels warm, but science defines heat as the flow of energy from a warm object to a cooler object. Actually, heat energy is all around us – in ...

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ARTICLE

Solids, liquids and gases

Water is the only common substance that is naturally found as a solid, liquid or gas. Solids, liquids and gases are known as states of matter. Before we look at why things are called solids ...

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Non-Newtonian fluids

Many people have heard of Sir Isaac Newton. He is famous for developing many scientific theories in mathematics and physics. Newton described how ‘normal’ liquids or fluids behave, and he ...

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Development of the periodic table

Although elements such as gold, silver, tin, copper, lead and mercury have been known since earliest times, the first scientific discovery of an element occurred in 1649. Hennig Brand, a German ...

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Carbon cycle

The carbon cycle can seem like a complex process because there are many interacting parts. Carbon is found in both organic (living) and inorganic (non-living) forms. Before we discuss the cycle ...

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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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ACTIVITY

What is the Earth system?

There are many interacting systems that make up the Earth, many of which are dynamic. These notes discuss the importance of understanding the concept of systems with emphasis on the water cycle ...

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The water cycle

The Earth has a finite amount of water. The water that is here today is the same water that will be here in 20 or even 20 million years’ time. So, if all living things use water, how is it that ...

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Ocean density

The density of seawater plays a vital role in causing ocean currents and circulating heat because of the fact that dense water sinks below less dense. Salinity, temperature and depth all affect ...

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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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ARTICLE

Insulation

In Antarctica, winter temperatures can vary from -70ºC to -15ºC – it is one of the coldest places to live on earth. To survive in the Antarctic, keeping warm becomes a very important focus, and ...

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ARTICLE

What is energy?

This is both a simple and complex question. Energy is in everything – it is often described as ‘the ability to do work’. Almost all food energy comes originally from sunlight. The chemical ...

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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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Water density

Water density changes with temperature and salinity. Density is measured as mass (g) per unit of volume (cm³). Water is densest at 3.98°C and is least dense at 0°C (freezing point). Why does ice ...

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Water and ice

Looking down at the Earth from space, you can get an idea of just how much water there is. In fact, around 71% of the Earth’s surface is covered in water. Oceans make up about 97% of the world’s ...

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ARTICLE

Viscosity

If you poured some water down a slope, it would flow freely and quickly, but what about if you repeated the process with honey? Can you imagine how honey would flow down a slope? Sticky oozy ...

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ARTICLE

Water and weather

The water cycle is driven by energy from the sun. Liquid water is evaporated and changed into a gas. In this process, energy is absorbed (endothermic). The gaseous vapour rises and circulates in ...

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ARTICLE

Metals, alloys and metal compounds

From titanium implants to new superconducting alloys to useful metal compounds, we are increasingly dependent on metals. Without metals, modern civilisation would literally collapse. About 80% of ...

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