Water and Energy

Unique properties of water molecules
A water molecule consists of two hydrogen atoms and one oxygen atom. The three atoms make an angle; the H-O-H angle is approximately 104.5 degrees. The center of each hydrogen atom is approximately 0.0957 nm from the center of the oxygen atom. In the solid state, the particles of matter are usually much closer together than they are in the liquid state. So if you put a solid into its corresponding liquid, it sinks. But this is not true of water. Its solid state is less dense than its liquid state, so it floats. Water behaves differently from most other chemical compounds. In almost all substances the atoms and molecules move closer together as they get colder. They then solidify. Water, however, attains its greatest density at four degrees Celsius because the water molecules are packed closest together at this temperature. Many freshwater lakes have a temperature of four degrees at their deepest point because the heavy water sinks to the bottom. But surprisingly, to reach the solid ice phase, the water molecules again move farther apart. This phenomenon is referred to as the water anomaly. Ice is lighter and floats at the surface. This is seen in the large ocean regions at polar latitudes, which are partly covered by ice. The reason for this anomaly lies in the unusual properties of the water molecule (H2O). Its oxygen atom (O) and the two hydrogen atoms (H) are asymmetrically arranged. This produces a dipole, a molecule with one negatively and one positively charged end.
Another unique property of water is its ability to dissolve a large variety of chemical substances. Water is sometimes called the universal solvent because it can dissolve so many things. water has the highest surface tension of any common liquid except mercury. It is the tendency of water molecules to attract to each other or cohere to each other at the surface of water. Because of this adhesion and cohesion properties water plays an important role in the internal transport system of plants and animals. The other widely-cited anomalous property of water is its high boiling point. a molecule as light as H2O “should” boil at around –90°C; that is, it would ideally exist in the world as a gas rather than a liquid if H-bonding were not present.

1of2

Describe the location of the areas with severe water shortage. 3 marks

Water

Theme 3.6

Candidates should be able to:Describe methods of water supply and the proportions of water used for agriculture, domestic and industrial purposes in countries at different levels of economic development.

Explain why there are water shortages in some areas and demonstrate that careful management is

required to ensure future supplies. Methods of water supply (including reservoirs/dams,

wells and bore holes, desalination). The impact of lack of access to clean water on local

people and the potential for economic development

Case Study required for 3.6: Water supply in a country or area

Water changes everything!

Water Walk

Cape Town Facing serious crisis

Global water crisis: Water-Energy-Food Nexus

Terminologies	Explanations	Self Research	Copy right free photos (thanks to the contributors)
Potable water	Water that is free from impurities such as contaminants and bacteria and is thus safe to drink. Huge inequalities persist between and within countries; in Sub- Saharan Africa, almost half of people drink water from unprotected sources.	There’s nothing more essential to life on Earth than safe drinking water. People are struggling to access the quantity and quality of water they need. Amazing progress has been made in making clean drinking water accessible to 2.6 billion people in developing countries from 1990 to 2015. That’s an increase from 76% of the global population to 91% during that time. Yet around 800 million people lack basic drinking water access that is nearly 1 of every 9 people on the planet. Click here for more facts and figures from World Vision.
Different methods of water supply	The objective of water supply is to take water from its source to the point of its usage. Water supply systems must also meet the requirements for public, commercial, and industrial activities. It generally denotes provision of water by public utilities such as supply of potable water through piped system. Water supply system include infrastructure for the collection, transmission, treatment, storage, and distribution of water for domestic, agriculture (including irrigation) and other commercial purposes as well as for special public needs as firefighting etc. Nearly 90% of the global population has access to piped water supply. A fraction of them also possess their own house supply such as protected wells or boreholes besides the municipal supply. Look at the next column for the the major methods of water supply.	1. Dam and reservoir: Dams are the barriers that controls the flow of the excess water, normally built across a river. Reservoirs are man made artificial lakes behind a dam that store water. They can be 'on channel' or 'off channel'. 2. Wells and boreholes: These are the methods of trapping ground water (Aquifer). Wells are relatively of larger diameter than boreholes. Aquifer provides nearly half of the global drinking water supply. 3. Desalinization plants: In this expensive process salt from the sea water is removed by distilling water using boiling process. This process is widely used in the wealthy Middle East countries where waste gasses from the oil wells are used to distill water. 4. Rain water harvesting: This includes collection and storing of rainwater for future use. Click here for more relevant information on the water supply system.	Water stress: When water supply is below 1700 cubic meters per person per year. Water scarcity affects every continent. Infographics from Waterlogic: Source Click here to learn more about the problem of water crisis from Water.org.
Water security	When all people in a society have sustainable access to adequate quantities of safe clean water for livelihood and development.	Read: Elements of water security from ResearchGate
Food security	Stable supply as well as physical, social, and economic access to sufficient, safe and nutritious food to meet the dietary needs of a population.

Mighty Three Gorges Dam

Rainwater Harvesting

Case: Desalinization in Israel

Task: Practice Exam type questions

Watch the video on the methods used to supply water in Singapore. Discuss in groups of two students and try to answer the question: For a named country, describe the methods used to supply water to the population (7 marks).

1of6

Methods of water supply in Germany

Most polluted water bodies

Drying up of Aral Sea

You will find more infographics at Statista

Energy: Important definitions

Natural Capital	Those goods and services that are not manufactured but have values to human, e.g. Soil, water, trees, living organisms etc.
Non-renewable energy	Exist in finite amount and are not renewed after they have been depleted, e.g. fossil fuels. These are forms of stored solar energy produced by photosysthesis (coal) and remains of organic life from millions of years ago, now being extracted and burned by humans.
Renewable energy	Can be used over and over again and are considered to be sustainable, e.g. Solar, wind, geothermal energy etc.
Replenishable resources	Are middle ground between renewable and non-renewable resources. They tend to be replaced over a long period of time. If the depletion rate is larger than recharge rate, the natural capital is depleted. E.g. Fuel wood.
Energy security	When all people in a society/country enjoy the uninterrupted supply of energy they require to meet their needs at an affordable price.