Answer:
It is true that earth was once covered with oceans and little dry land.
Explanation:
Over the course of around four billion years, the Earth's oceans have lost about a quarter of their original mass. Today the atmosphere is rich in oxygen, which reacts with both hydrogen and deuterium to recreate water, which falls back to the Earth's surface. So the vast bulk of the water on Earth is held in a closed system that prevents the planet from gradually drying out. According to the researchers, the continents emerged relatively suddenly from an ocean that covered 95 percent of the Earth's surface. The appearance of large masses of dry land would have caused more extreme weather, changes in ocean currents and the emergence of proper seasons. In turn, these environmental changes may have led to rise in atmospheric oxygen that enabled the explosion of new life forms around 500 million years ago.
Answer:
poisoning, breathing problems, skin rashes, allergic reactions, allergic sensitisation, cancer, and other health problems from exposure.
Explanation:
many hazardous chemicals are also classified as dangerous goods.
Answer:
A solvent is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid.
Explanation:
Answer: The amount of energy needed to move an electron from one zone to another is a fixed, finite amount. The electron with its extra packet of energy becomes excited, and promptly moves out of its lower energy level and takes up a position in a higher energy level.
Explanation:
Answer:
Anthracite
Explanation:
Anthracite produce highest amount of energy than other. It contain 86-97 percent carbon. Bituminous coal contain 45-86 percent carbon.
Subbituminous cola have 35-45 percent carbon while lignite contain 25-35 percent carbon.
Coal is source of many organic materials. It is fossil fuel and form after long period decay of plants. It is formed when trees are buried under earth
about 500 million years ago. The chemical and bacterial reactions take place and plant wood converted into the peat.
Than because of high temperature and pressure inside the earth peat is converted into the coal.
Through other processes it is than used to make the fuels such as coke. coal tar and coal gas.
Coal tar is the source of many organic compounds which are separated through fractional distillation.
About 80% of coal in Pakistan is used to bake the bricks and also used in lime kilns and for domestic purpose.
