The component of an atom that possesses relatively little mass, thus being negligible in calculating the atomic mass number, is the

A. When water dissolves sugar, it is a physical change rather than a chemical reaction. The water molecules surround the sugar molecules and allow them to disperse throughout the solution, but the chemical structure of neither the water nor the sugar changes.

B. When water reacts with sodium metal, it is indeed a chemical reaction. This reaction is quite vigorous and exothermic, producing hydrogen gas and sodium hydroxide. The reaction can be represented by the chemical equation 2Na + 2H2O 2NaOH + H2. This is a classic example of a single displacement reaction where the metal takes the place of hydrogen in water.

C. Boiling water to produce steam at 100° C (212° F) is a physical change. Here, the water is changing its state from liquid to gas due to the input of heat. However, the molecular structure of water H2O remains the same before and after boiling.

D. The separation of water and oil when combined is also a physical process. This occurs because water is polar, meaning it has a slight charge difference across its molecule, while oil is non-polar and does not mix with water. This difference in polarity leads to the formation of separate layers, with oil typically floating on top of the water due to its lower density, but no chemical reaction occurs between the two substances.

A. A centrifuge is a device that separates components in a liquid by spinning at high speed, which forces heavier materials to the outer edge of the spinning container. It is not typically used to measure turbidity.

B. A spectrophotometer is an instrument that measures the amount of light that passes through a sample. It is commonly used to measure turbidity because it can quantify how much light is absorbed by suspended particles in the liquid.

C. A microdensitometer is used to measure the density of microscopic particles on photographic or radiographic film, which is not directly related to the measurement of turbidity in a liquid.

D. An electrophorometer is an instrument used to measure the rate of movement of charged particles in a fluid under the influence of an electric field. It does not measure turbidity or the transmission of light through a sample.

A. A hypothesis is a proposed explanation for an observation, which can then be tested through experimentation. The scientific method is structured around the falsifiability of hypotheses; that is, for a hypothesis to be scientific, it must be possible to conceive an observation or an argument which could negate it. This principle is encapsulated in the statement that "experiments cannot validate hypotheses, only falsify them." Therefore, a hypothesis that has not been falsified remains provisional, meaning it is accepted as a possible explanation but is not confirmed until all attempts to falsify it have failed

B. This is a common misunderstanding of the scientific process. While it is true that a hypothesis remains accepted until evidence to the contrary is found, this does not mean the hypothesis is valid, only that it has not yet been invalidated. Validity in science is not about the absence of disproof but the presence of empirical support.

C. Proving a hypothesis is not the aim of scientific inquiry. Science advances by disproving hypotheses, not proving them. Even after a hypothesis has survived multiple tests and has not been falsified, it is still subject to further testing and scrutiny. No hypothesis is exempt from this process, as future evidence may provide new insights or contradictions.

D. This diverts from the original statement by introducing the concept of concepts not being directly testable. While this is a valid point in the philosophy of science, it does not restate the original claim about the role of experiments in validating hypotheses. Some concepts may indeed be theoretical and not directly testable, but this does not reflect on the principle of falsifiability as the core of the scientific method.

A. The myocardium, is the thick, muscular middle layer of the heart's walls and is responsible for the pumping action of the heart due to its contractile cardiomyocytes.

B. The pericardium is the fibrous sac that encloses the heart providing protection and anchoring the heart within the thoracic cavity.

C. The epicardium is the outermost layer of the heart wall, also known as the visceral layer of the serous pericardium, and it provides an additional layer of protection and contains the blood vessels and nerves that supply the heart tissue.

D. The endocardium is the thin inner lining of the heart chambers and also forms the surface of the valves. It is comprised of endothelial cells and a layer of subendocardial connective tissue, which is continuous with the connective tissue of the myocardium. This layer is essential for providing a smooth lining for the chambers of the heart and the heart valves, ensuring efficient blood flow and minimizing turbulence within the heart.

A. Identifying routes for future climbs is a valid reason for an expedition, but it does not directly address the historical context of the 1924 expedition.

B. Measuring oxygen levels at high elevations is a scientific endeavor that can be conducted without the specific context of replicating an earlier climb.

C. By taking the same route, in the same season, and with similar materials and equipment as the 1924 expedition, the mountaineer is likely attempting to understand the variables and challenges faced by the original team, which could provide insights into the reasons behind the failure of that expedition.

D. Demonstrating the efficacy of modern technology in making climbing safer is a plausible objective, but it does not require the replication of the conditions of the 1924 expedition. Modern expeditions typically use current technology and techniques to enhance safety, rather than deliberately using outdated methods.

A. The rate of fall is affected by mass of the object, since object D and C fall at a faster rate than A. However it is important to consider other factors such as shape and size of the object.

B. Although objects A and B have the same mass, they do not fall at the same rate, as evidenced by their different times of fall.

C. The data does not support the conclusion that greater mass leads to a faster fall. Object C, with a mass of 30.0g, falls in 0.5sec, while object D, with a greater mass of 35.0g, falls in a longer time of 1.5sec.

D. A and B have the same mass but have different rates of fall. This indicates that air resistance is greater for A, hence the slower rate of fall.

A. A pivot joint allows for rotational movement around a single axis. An example of a pivot joint is the atlantoaxial joint in the neck, which allows for the rotation of the head.

B. A hinge joint permits movement in one plane, much like the opening and closing of a door.

C. The elbow and knee joints are classic examples of hinge joints, allowing for flexion and extension.

D. Gliding joints, also known as plane joints, allow for sliding movements in multiple directions within a plane. These are found in areas like the carpals of the wrist, where small bones slide against each other to allow for a range of movements.

The hip joint is a ball-and-socket joint, which is characterized by a spherical end of one bone fitting into a cup-like depression of another bone. This structure allows for a wide range of motion, including flexion, extension, abduction, adduction, and rotation. The hip joint, specifically, is formed by the articulation of the head of the femur and the acetabulum of the pelvis. It is designed for stability and weight-bearing, making it one of the most stable joints in the human body. This type of joint is also found in the shoulder, where the humerus fits into the glenoid fossa of the scapula.

A. Skeletal muscles are not autorhythmic; this term refers to the ability to generate a rhythmical electrical impulse without the need for nervous stimulation, which is a characteristic of cardiac muscles.

B. Cardiac muscles contain intercalated discs, which are unique structural formations that allow for the rapid transmission of electrical impulses between cardiac cells. This feature is not found in skeletal muscles, which are composed of individual muscle fibers that are controlled voluntarily.

C. Cardiac muscles are involuntary, meaning they function without conscious control, which is necessary for the continuous pumping action of the heart. In contrast, skeletal muscles are under voluntary control, allowing for movement of the body in response to conscious decisions.

D. Skeletal muscles are not found in the viscera; they are attached to bones and are responsible for body movements. Cardiac muscles, on the other hand, are located in the heart, which is not in the cranium but in the thoracic cavity. The term 'viscera' refers to the internal organs in the main cavities of the body, especially those in the abdomen, not the cranium.

A. This option changes the population, which could introduce new variables related to gender differences in metabolism or physical performance.

B. This option introduces another variable by using two different energy drinks, which could have different ingredients and effects.

C. This option changes the distance run, which could affect the endurance aspect rather than the speed.

D. To best support the conclusion that energy drinks increase the speed of running in women, it would be most effective to conduct a controlled experiment where a variable is changed while others are kept constant. By giving half of the women water and the other half the energy drink, researchers can directly compare the effects of the energy drink against a baseline (water), which has no enhancing properties on running speed. This comparison would help to isolate the effect of the energy drink on running performance

A. This plate represents good antibiotic activity against Escherichia.

B. This is the plate that represents the highest number of bacteria. The bacteria that grow on this plate are the most resistant to the antibiotic because they can survive in a high concentration of the substance. In the other plates, the antibiotic inhibits the growth of the bacteria to a greater or lesser extent, depending on their sensitivity.

C. This plate represents partial antibiotic activity against Escherichia.

D. This represents no activity that may be due to inappropriate media.