Topics
Chemical Substances - Nature and Behaviour
Carbon Compounds
- Carbon: a Versatile Element
- Bonding in Carbon - Covalent Bond
- Carbon: a Versatile Element
- Saturated and Unsaturated Carbon Compounds
- Chains, Branches and Rings of Carbon Compound
- Homologous Series of Carbon Compound
- Nomenclature of Carbon Compounds
- Chemical Properties of Carbon Compound
- Chemical Properties of Carbon Compound
- Chemical Properties of Carbon Compound
- Ethanol
- Ethanoic Acid
- Soap
- Chemical Properties of Carbon Compound
Metals and Non Metals
- Types of Element: Metals
- Types of Elements: Non-metal
- Chemical Properties of Metals: When Metals Are Burnt in Air
- Chemical Properties of Metals: When Metals React with Water
- Chemical Properties of Metals: When Metals React with Acids
- Chemical Properties of Metals: Metals React with Solutions of Other Metal Salts
- Chemical Properties of Metals: Reactivity Series
- Reaction of Metals with Non-metals
- Formation and Properties of Ionic Compounds
- Types of Element: Metals
- Extraction of Metals from Ore
- Enrichment of Ores
- Extracting Metals Low in the Activity Series
- Extracting Metals in the Middle of the Activity Series
- Extracting Metals Towards the Top of the Activity Series
- Refining of Metals
- Corrosion of Metals and Its Prevention
- Covalent (Molecular) Bond
Periodic Classification of Elements
Acids, Bases and Salts
- Acids
- Bases (Alkalis)
- Indicators
- Chemical Properties of Acids and Bases
- Reaction of Acids and Bases with Metals
- Reaction of Acids with Metal Carbonates and Hydrogencarbonates
- Reaction of Metallic Oxides with Acids
- Reaction of a Non-metallic Oxide with Base
- Acids and Bases React with Each Other
- Acid Or a Base in a Water Solution
- Strength of Acidic Or Basic Solutions
- Salts
- Salts
- Chemicals from Common Salt (Uses of Salt)
- Preparation and Uses of Sodium Hydroxide
- Preparation and Uses of Bleaching Powder
- Preparation and Uses of Baking Soda
- Preparation and Uses of Washing Soda
- Preparation and Uses of Plaster of Paris
Chemical Reactions
- Classification of Change: Physical Changes
- Classification of Change: Chemical Changes
- Classification of Change: Chemical Changes
- Chemical Equation
- Chemical Equation
- Direct Combination (or Synthesis)
- Decomposition Reactions
- Single Displacement Reactions
- Double Displacement Reaction
- Oxidation and Reduction
- Corrosion of Metals and Its Prevention
- Concept of Rancidity
- Endothermic and Exothermic Reactions
World of Living
Heredity and Evolution
- Evolution and Classification - Introduction
- Accumulation of Variation During Reproduction
- Heredity - Inherited Traits
- Rules for the Inheritance of Traits - Mendel’S Contributions
- Sex Determination in Humans
- Concepts of Evolution
- Evolution - Acquired and Inherited Traits
- Speciation
- Heredity and Evolution
- Evolution and Classification - Tracing Evolutionary Relationships
- Evolution and Classification - Fossils
- Evolution by Stages
- Human Evolution
Reproduction
- Reproduction in Plant
- Reproductive Health - Need and Methods of Family Planning
- Modes of Reproduction Used by Single Organisms - Fission
- Modes of Reproduction Used by Multicellular Organisms - Fragmentation
- Modes of Reproduction Used by Multicellular Organisms - Regeneration
- Modes of Reproduction Used by Single Organisms - Budding
- Modes of Reproduction Used by Multicellular Organisms - Vegetative Propagation
- Modes of Reproduction Used by Multicellular Organisms - Spore Formation
- Sexual Reproduction in Animals
- Sexual Reproduction in Flowering Plants
- Human Reproductive System
- Reproduction in Plant
- Sexually Transmitted Diseases
Control and Co-ordination in Animals and Plants
- Control and Co-ordination Introduction
- Tropic Movements in Plants
- Coordination in Plants - Movement Due to Growth
- Coordination in Plants - Immediate Response to Stimulus
- Hormones in Animals
- Control and Co-ordination in Animals
- Importance of Variation
- Animals – Nervous System
- Human Brain - Voluntary Action
- Human Brain - Involuntary Action
- Human Brain - Reflex Action
- Control and Co-ordination Questions
Life Processes
Natural Phenomena
- Refraction of Light
- Spherical Mirrors
- Concave Mirror
- Convex Mirror
- Concave Mirror
- Convex Mirror
- Sign Convention for Reflection by Spherical Mirrors
- Linear Magnification (M) Due to Spherical Mirrors
- Velocity of Light
- Refraction of Light
- Refraction Through a Rectangular Glass Slab
- Refractive Index
- Refraction by Spherical Lenses
- Convex Lens
- Concave Lens
- Convex Lens
- Concave Lens
- Sign Convention for Spherical Lenses
- Magnification of a Lens
- Power of a Lens
- Human Eye: Structure of the Eye
- Eye Defect and Its Correction: Myopia Or Near-sightedness
- Applications of Spherical Mirrors and Lenses
- Dispersion by a Prism
- Atmospheric Refraction
- Some Natural Phenomena Due to Sunlight
Effects of Current
Magnetic Effects of Current
- Magnetic Effect of Electric Current
- Magnetic Field Lines
- Magnetic Force
- The Bar Magnet
- Magnetic Field Due to a Current carrying Straight Conductor
- Right-Hand Thumb Rule
- Magnetic Field Due to a Current Through a Circular Loop
- Magnetic Field Due to a Current in a Solenoid
- Force on a Current Carrying Conductor in a Magnetic Field
- Fleming’s Left Hand Rule
- Electric Motor
- Electromagnetic Induction
- Alternating Current (A.C.) Generator
- Domestic Electric Circuits
- Types of current: Alternating Current (A.C.) and Direct Current (D.C.)
- Introduction of Magnetism
Effects of Current
Natural Resources
Management of Natural Resources
- Conservation and Judicious Use of Natural Resources
- Need to Manage Our Resources
- Forests and Wild Life - Stakeholders
- Forests and Wild Life - Sustainable Management
- Coal and Petroleum
- Water for All - Dams
- Water for All - Water Harvesting
- Overview of Natural Resource Management
- Sustainability of Natural Resources
- Fresh Water Management
Our Environment
Sources of Energy
- Sources of Energy Introduction
- Good Source of Energy
- Different Forms of Energy
- Conventional Sources of Energy
- Heat Energy (Thermal Energy)
- Hydroelectric Energy
- Improvements in the Technology for Using Conventional Sources of Energy
- Solar Energy
- Alternative or Non-conventional Sources of Energy - Energy from the Sea
- Alternative Or Non-conventional Sources of Energy - Geothermal Energy
- Nuclear Energy
- Environmental Consequences
- Energy Source - How Long Will Last Us
- Renewable and Non-renewable Energy Resources
description
- Big dams: advantages and limitations,
- Big dams: alternatives, if any
notes
ADVANTAGES:
1. Once a dam is constructed, electricity can be produced at a constant rate.
2. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high.
3. Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades.
4. The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right.
5. The lake's water can be used for irrigation purposes.
6. The build up of water in the lake means that energy can be stored until needed, when the water is released to produce electricity.
7. When in use, electricity produced by dam systems do not produce green house gases. They do not pollute the atmosphere.
DISADVANATGES:
1. Dams are extremely expensive to build and must be built to a very high standard.
2. The high cost of dam construction means that they must operate for many decades to become profitable.
3. The flooding of large areas of land means that the natural environment is destroyed.
4. People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead.
5. The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earths surface at its location.
6. Although modern planning and design of dams is good, in the past old dams have been known to be breached (the dam gives under the weight of water in the lake). This has led to deaths and flooding.
7. Dams built blocking the progress of a river in one country usually means that the water supply from the same river in the following country is out of their control. This can lead to serious problems between neighbouring countries.
8. Building a large dam alters the natural water table level. For example, the building of the Aswan Dam in Egypt has altered the level of the water table. This is slowly leading to damage of many of its ancient monuments as salts and destructive minerals are deposited in the stone work from rising damp caused by the changing water table level.
Alternatives:
- biomass gasifiers, which burn waste products from agricultural production (such as rice or corn husks) to produce electricity
- small-scale micro- (<100kw) and pico-hydro (<5 kw), which require no dam and run on the river’s natural flow
- solar and wind generation
- co-generation, a combination of electricity, heating and cooling from waste heat, usually sited to consumer needs. Surplus can be shared/sold to nearby customers using low voltage systems