Science

Refine Search

What is thyroid disease?

Hyperthyroidism occurs when the thyroid gland is overactive and produces too many hormones. The most common cause of hyperthyroidism is Graves' disease, an autoimmune disorder which stimulates the thyroid to produce too many hormones.\nHypothyroidism occurs when the thyroid gland does not make enough hormones. Hypothyroidism may also cause high blood levels of LDL cholesterol, sometimes called the "bad" cholesterol. The most common cause of hypothyroidism in the United States is Hashimoto's disease.\nThyroid nodules cause swelling in one section of the thyroid gland. These nodules ma..

Continue Reading

What is simple distillation?

The distillation process is said to have originated from the ancient Arab chemists around 3500 B.C.E. These early scientists used the technique to separate the components of perfume. In modern times, this process typically involves a distillation apparatus consisting of a boiling flask, collection flask, water supply tube, drainage tube, condenser and thermometer. The individual components of a compound separate, after being distilled, due to differences in boiling points. Other forms of distillation include fractional distillation and vacuum distillation.

Continue Reading

What are examples of exothermic phase changes?

Chemistry at About.com explains the endothermic and exothermic processes. In order to determine if a phase change is endothermic or exothermic, consider the energy levels of the atoms in both the initial and final states. For an exothermic reaction, the atoms in the initial state have more energy, which is typically indicated by greater kinetic energy. For instance, water moves more than ice because the molecules in water have more kinetic energy. Likewise, water molecules in water vapor move even more than those in liquid water. In order to condense water vapor to water, the molecules must lo..

Continue Reading

What muscles are used in sprinting?

The gluteus maximus and hamstring muscles contract and are responsible for the force that drives the leg backwards during sprints. The gluteus maximus is the largest and strongest muscle in the body, originating at the pelvic bone, fanning down and out and inserting at the top of the femur bone. The hamstrings originate at the pelvic bone, run down the back of the thigh and insert at the back of the tibia bone. The quadriceps are responsible for straightening the knee joint after it strikes the ground. They originate at the pelvic bone and run down the front of the thigh inserting at the top o..

Continue Reading

What causes erosion?

The rate at which soil erodes depends on the area's climate, topography, soil type, land management practices and vegetative cover. Removing the vegetative cover accelerates erosion, which is often caused by grazing, logging or cultivating. In some cases, it can be removed by pests like pigs, rabbits and goats. When the vegetation is removed, huge amounts of soil are lost through erosion, especially in times of storms. The eroded soil is normally washed into waterways, and this leads to decreased clarity of water. Once the eroded soil is in the waterways, it can choke life such as fish, a..

Continue Reading

How do you view a labeled diagram of the human heart?

The 2D interactive diagram on InnerBody.com includes several viewing angle options. Hover the mouse pointer over a section of the heart, vein or artery to see the part's name and information. To use the site's 3D diagram, click and hold the plus and minus signs to zoom. Drag the diagram to rotate it, and click a part of the heart to see its name.\nThe diagram at WebMD.com includes a simple picture, a cross-section and basic information about the heart.

Continue Reading

How did Einstein contribute to atomic theory?

In addition to predicting atomic size, 1905 was the year that Einstein released his specialized theory of relativity as well as several other papers that were invaluable to the expansion of physics and chemistry. In the same year, Einstein also accurately calculated both the diameter of a sugar molecule and Avogadro's number.

Continue Reading

Can small wind turbines be used to power a home?

Home wind turbines should be installed at least 30 feet above any obstructions, and the average height of a small wind turbine is about 80 feet. While specific requirements vary from location to location, wind turbines should be placed in an area with average wind speed of at least 12 miles per hour. Zoning regulations may limit who can install a wind turbine, and people rarely use them in urban settings due to zoning restrictions and wind obstructions.

Continue Reading

What is the difference between a pure substance and a mixture?

Both pure substances and mixtures can exist as solids, liquids or gases. Most ordinary things are mixtures with at least two types of molecules. For example, air is a mixture of pure substances, including nitrogen, oxygen and carbon dioxide. Apple juice is another common mixture that includes particles of water, sugar, flavoring and vitamins.

Continue Reading

Why don't pine trees lose their needles?

Coniferous trees, such as the pine, have needle-like leaves that are less efficient in gathering sunlight but can photosynthesize all year long. The thin leaves are watertight and thick enough to survive the frost of winter, and they have a resin coat that makes them less tasty to insects. Because of these characteristics, the needles of a pine tree can stay in the tree without falling off the branches for several years.

Continue Reading
Showing 7441 to 7450 of 10000 (1000 Pages)