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ARTICLE

H₂O on the go, the water cycle – introduction

Earth is called the blue planet due to the abundance of water. About 70% of the surface of the Earth is covered by water, and it is the only natural substance that can be found on Earth in all ...

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ARTICLE

Observing water – introduction

Use these Material World resources for NZ Curriculum levels 1 and 2 to explore the characteristics of solids, liquids, gases and bubbles by observing water and its unusual properties. Observation ...

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ARTICLE

Water

Water seems to be everywhere in New Zealand. Oceans surround us. There are hundreds of lakes and rivers. Some South Island regions get more than 10 metres of rain each year. We have so much ...

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ARTICLE

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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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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ARTICLE

Marine food webs

Feeding relationships are often shown as simple food chains – in reality, these relationships are much more complex, and the term ‘food web’ more accurately shows the links between producers ...

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Humans and the water cycle

We are becoming increasingly aware of our impacts on nature, but unfortunately many of the things we do have become so ingrained in our way of life that it is hard to change. Different countries ...

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ARTICLE

Ocean salinity

There are many chemicals in seawater that make it salty. Most of them get there from rivers carrying chemicals dissolved out of rock and soil. The main one is sodium chloride, often just called ...

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Human impacts on marine environments

Throughout human existence we have relied on the oceans – for food, as a waste dump, for recreation, for economic opportunities and so on. However, it’s not only our activities in the marine ...

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ARTICLE

Adaptations of marine organisms

Adaptation is an evolutionary process whereby an organism becomes increasingly well suited to living in a particular habitat. It is not a quick process! Natural selection over many generations ...

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Human impact on rivers

Human beings have an impact on river ecosystems. The relationship living organisms have with each other and with their environment is extremely complex. Impacts on a species or a non-living ...

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Ocean dissolved gases

Seawater has many different gases dissolved in it, especially nitrogen, oxygen and carbon dioxide. It exchanges these gases with the atmosphere to keep a balance between the ocean and the ...

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River ecosystems

The ecology of the river refers to the relationships that living organisms have with each other and with their environment – the ecosystem. An ecosystem is the sum of interactions between plants ...

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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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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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Ocean temperature

The temperature of the ocean determines what form the water takes. Most of the ocean is liquid water, but if it gets cold enough, it turns to solid ice, or if it gets hot enough, it can pass into ...

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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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Environmental conditions affecting the sea

On land, the most important environmental conditions affecting organisms are rainfall and temperature. In our oceans, there are a number of environmental conditions that affect the growth ...

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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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