Star is a brilliantly glowing sphere of hot gas whose energyis produced by an internalnuclear fusion process. Stars are contained in galaxies. A galaxy contains not only stars, but clouds of gas and dust. These clouds are callednebulae, and it is in a nebula where stars are born. In the nebula is hydrogen gas which is pulled together by gravityand starts to spin faster. Over millions of years, more hydrogen gas is pulled into the spinning cloud. The collisions which occur between the hydrogen atoms starts to heat the gas in the cloud. Once the temperature reaches 15,000,000 degrees Celsius, nuclear fusion takes place in the center, or core, of the cloud. The tremendous heat given off by the nuclear fusion process causes the gas to glow creating a protostar. This is the first step in the evolution of a star. The glowing protostar continues to accumulate mass. The amount of mass it can accumulate is determined by the amount ofmatter available in the nebula. Once its mass is stabilized, the star is known as a main sequence star. The new star will continue to glow for millions or even billions of years. As it glows, hydrogen is converted into helium in the core by nuclear fusion. The core starts to become unstable and it starts to contract. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and starts to glow red. The star has now reached the red giant phase. It is red because it is cooler than the protostar phase and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths the star will take.
Answer:
First law of thermodynamics is the conservation of energy states that energy is not created and not destroyed but only can be stored.
Thermodynamics second law states that total entropy of a system increases from lower to higher system and some of the energy is always wasted during the work done.
In the food chain plants are the producers which accept light energy and stored in the form of chemical energy and energy flow to the herbivores and higher trophic levels in the chemical form only and no new energy is created in between the chain (Fisrt law of thermodynamics). Heat is generated during respiration by plants and animals (wasted energy) and entropy also increases with the increase in level of the pyramid of energy (Second law of thermodynamics).
Answer:
Substance
<u>Review</u>:
⇒ One of a class of substances that cannot be separated into simpler substances by chemical means.
<u>Compound</u>:
⇒ A pure substance composed of two or more elements who composition is constant.
Exposure to environmental tobacco smoke causes approximately 45 to 46,000 non smokers to die of heat diseases annually. Smoking harms the cardiovascular system in many ways which include; damaging the lining of arteries, reduces HDL, good choresterol, Raises LML, bad cholesterol, increases blood pressure and heart rate, it also causes the platelets to stick together in the blood stream and speeds the development of fatty deposits in the arteries among other risk factors.
