Science

Refine Search

Do arteries have valves?

The heart pumps blood around the body. Arteries move oxygenated blood away from the heart, while veins transport de-oxygenated blood back to the heart. Most blood is pooled in veins, which means it's likely to collect. As a result, veins need valves to prevent the backflow of blood. This contrasts with arteries, which are thick, strong and able to withstand the high pressure the heart demands.

Continue Reading

What are the most active metals?

In terms of relative reactivity, metallic elements are classified into four groups: active, less active, structural and coinage. Active metals are characterized by their tendency to readily combine with gaseous oxygen and atmospheric water vapor. Due to this highly reactive nature, these elements are commonly stored in an inert fluid material, such as petroleum-derived oil.Less active metals include magnesium, zinc, aluminum and manganese. Although these elements are not likely to bond with water at normal temperatures, less active metals quickly combine with acidic compounds.

Continue Reading

How do you make things float?

Locate a sealed containerFind a container that has empty space. To float, the combination of the object and the container must have a greater ratio of empty space to mass than the fluid, so choose the container size accordingly. Ensure that the container is sealed so that fluid cannot enter it.Attach the containerFasten the container to the object securely.Place the object in the fluidPut the combined object and container in the fluid. If enough empty space exists in the securely fastened and sealed container, the object floats.

Continue Reading

What are the main uses of hydrochloric acid?

Hydrochloric acid is a colorless, highly pungent solution comprised of hydrogen chloride and water. A highly corrosive mineral acid, hydrochloric acid has numerous industrial uses. Hydrochloric acid is used throughout the chemical industry and for large-scale production of vinyl chloride, the material used to produce PVC plastic. Originally known as muriatic acid or spirits of salt, widespread production of hydrochloric acid began during the Industrial Revolution.

Continue Reading

How can you make pure hydrogen?

Obtain a direct current sourceUse a rectangular 9-volt battery, also called a transistor battery, and note the polarity on the terminals.Make a solution of water and saltDissolve 1 tablespoon of table salt in a gallon of tap water. The salt helps conduct electricity, improving the result. Create a collection systemUse a glass or ceramic bread baking pan, and fill it with the salted water. Take two small glass jars or test tubes and submerge them in the pan of water. Invert the jars, making sure no air is trapped inside.Connect the batteryUse two wires and connect one to each pole on the batter..

Continue Reading

What gives plants their green color?

The color of any substance depends on the energy levels of the atoms and molecules that comprise it, as well as the spectrum of the incoming light. If an object is blue, it is because it reflects blue light and absorbs the rest, which raises the electrons in its atoms to a higher energy level in a process called excitation.

Continue Reading

Why does my arm go numb when I sneeze?

Vertebral disks act as cushions between the vertebral bodies of the spinal column. If damaged, they may herniate, impinging the nerve in the direction of the bulge. WebMD explains that disks can herniate due to wear and tear, as well as after traumatic injury such as a car accident.\nWebMD emphasizes the importance of talking to a doctor if symptoms such as numbness, pain or weakness occur, even if only after sneezing or coughing. The appointment will typically consist of a thorough clinical history and a physical exam. The physician may order an x-ray, magnetic resonance imaging or a myelogr..

Continue Reading

How do you hear through walls?

Sound travels in waves that change as they meet different surfaces. The more pores a surface has, the more sound that surface absorbs; the thicker a surface is, the more sound that surface reflects. Many walls feature a thin veneer with a hollow interior, so while some echoing occurs, much of the sound continues through into the cavity inside the wall, and then through the veneer on the other side.\nAdding insulation to the inside of a wall reduces the amount of sound that passes through it. All sound waves lose power over time, and insulation and other porous materials absorb sound. The waves..

Continue Reading

What is the formula for velocity?

The formula for velocity given constant acceleration is v = u + at, where u is the velocity when the time, t, is equal to 0 and a is the rate of acceleration. The acceleration can be expressed as the change in velocity over the change in time. The instantaneous velocity can be found by taking the derivative of the equation in respect to distance. In this case, velocity and speed are the same, except that velocity is expressed as vector and speed is expressed in scalar form.

Continue Reading

Is carbon dioxide polar or nonpolar?

Carbon dioxide has a central carbon atom that has two oxygen atoms arranged at a 180 degree angle from each other, making it a linear molecule. Carbon forms a double bond with each oxygen atom. Since carbon and oxygen have different electronegativities, the electrons are not shared equally between the two atoms. Oxygen, with its higher electronegativity, pulls the bonded electrons closer to itself. Thus, each oxygen atom has a partial negative charge, and the carbon has a partial positive charge. However, due to the symmetrical, linear arrangement of the molecule, the individual bond polaritie..

Continue Reading
Showing 411 to 420 of 10000 (1000 Pages)