Praxis Test
ption (A) is correct. According to the balanced equation, 2 moles of H2OH 2 O decompose to give 2 moles of H2H 2. Since 9 g H2O × (1 mol H2O/18 g H2O) = 0.5 mol H2O, then 0.5 mol H2O × (2 mol H2/2 mol H2O) = 0.5 moles9 grams of H 2 O, times one mole of H 2 O over 18 grams of H 2 O, equals zero point 5 mole of H 2 O, then zero point 5 mole of H 2 O, times 2 moles of H 2 over 2 moles of H 2 O, equals zero point 5 moles of hydrogen gas produced.
2 H2O(l) →→ 2 H2(g) + O2(g) If 9 g of H2OH 2 O decomposes according to the reaction shown above, how many moles of hydrogen gas are produced? A.0.5 mol B.1 mol C.2 mol D.4 mol
Option (D) is correct. By energy conservation, the sum of the cart's kinetic energy and potential energy is a constant (assuming negligible energy loss due to friction and air resistance). As the cart moves up the hill, its kinetic energy will decrease and its potential energy will increase. If the cart just reaches the top of the hill, then the cart will be at rest at the top of the hill and will have only potential energy at that point; that is, its initial kinetic energy at the base of the hill will have been converted entirely into potential energy at the top of the hill. Thus the minimum kinetic energy of the cart is equal to 10 kg × 10 m/s2 × 4.0 m = 400 joules10 kilograms times 10 meters per second squared, times 4 point zero meters, equals 400 Joules.
A 10 kg10 kilogram cart is rolling along the surface shown in the figure above. What is the minimum kinetic energy of the cart at the base of the hill if it is going to be able to roll to the top of the upper level? (Assume g = 10 m/s2 g equals, 10 meters per second squared.) A.4 joules B.10 joules C.40 joules D.400 joules
Option (B) is correct. Phagocytic cells engulf and digest large particulate materials (e.g., destruction of bacteria by macrophages or neutrophils). Lysosomes are organelles that contain hydrolytic enzymes and function in intracellular digestion.
A phagocytic white blood cell will most likely have more of which of the following organelles than a muscle cell will? A.Ribosomes B.Lysosomes C.Golgi apparatus D.Endoplasmic reticulum
Option (C) is correct. The neurons primarily responsible for regulating breathing are located in the medulla oblongata, near the base of the brain stem. Neural circuits in the respiratory control center detect stretching of the lungs and regulate the degree of lung expansion during inhalation. Neurons in the medulla also use the pH of the blood as an indicator of the necessary depth and rate of breathing. Increased metabolic activity causes an increase in blood CO2C O 2, which dissociates into HCO3- and H+H C O 3 negative one ion and H plus. This causes a decrease in the pHp H of the blood and of the cerebrospinal fluid that bathes the central nervous system.
A respiratory control center is located in which of the following structures? A.Heart B.Pulmonary artery C.Medulla oblongata D.Spinal cord
Option (B) is correct. If the half-life of the substance is 10 years, then every 10 years the amount of the isotope is decreased by half. Thus, it requires three half-lives, or 30 years, for the isotope to decay until approximately 1 gram remains in the sample.
A sample contains 8 g of a radioisotope that has a half-life of 10 years. How much time is required for the sample to decay until approximately 1 gone gram of the isotope remains in the sample? 10 years 30 years 80 years 800 years
Option (C) is correct. The volume of liquid water generally increases in very small increments with increasing temperatures. Since the water is in the liquid state and not in the gaseous state, the volume of the sample at 80°CC is most likely 1,027 mL, only slightly larger than the volume of the sample at 20°C
A sample of liquid water of a certain mass at 20°C and 1 atm20 degrees Celsius and one atmosphere has a volume of 1,000 mL. Which of the following is the most likely volume of a water sample with the same mass at 80°C and 1 atm80 degrees Celsius and one atmosphere? A. 970 mL B.1,000 mL C.1,027 mL D.4,000 mL
Option (C) is correct. In order to draw a valid conclusion about the effect of water on seed germination, the student should have included a control experiment, a second dish with a dry paper towel, in the investigation. The only experimental variable should be the presence or absence of water. The control variables, light and temperature, should be the same for both dishes.
A student placed 20 radish seeds on a damp paper towel in a petri dish and placed the dish under a fluorescent light. After 48 hours, all the seeds had germinated. In order for the student to draw a valid conclusion about the effect of water on seed germination, which of the following should also have been included in the investigation? a. A second dish should have been placed in the dark. b. A second dish should have been placed in a refrigerator. c. A second dish with a dry, rather than damp, paper towel should have been used. d. A second dish with a dry, rather than damp, paper towel should have been placed in direct sunlight on a windowsill.
Option (C) is correct. For any marked measuring device, one place beyond the numerical place of the marking is estimated, and this determines the correct number of significant figures. If the thermometer is marked to 0.1°Czero point one degrees Celsius, the hundredth place should be estimated and the temperature recorded as 22.44°C22 point four four degrees Celsius.
A thermometer inserted into a solution has a mercury level of just a bit less than halfway between the markings for 22.4ºC22 point 4 degrees Celsius and 22.5ºC22 point 5 degrees Celsius. To represent the correct number of significant figures, the temperature of the solution should be recorded as: a. 22 b. 22.4 c. 22.44 d. 22.5
Option (B) is correct. Newton's third law states that for every action, there is a reaction force that is equal in magnitude but opposite in direction to the action force. Thus the force that the wagon exerts on the tractor must be equal in magnitude to the force that the tractor exerts on the wagon.
A tractor is pulling a wagon full of hay. The mass of the wagon and hay is two times the mass of the tractor. When the tractor accelerates forward, the force that the wagon exerts on the tractor is a. two times greater in magnitude than the force that the tractor exerts on the wagon b. equal in magnitude to the force that the tractor exerts on the wagon c. one-half the magnitude of the force that the tractor exerts on the wagon d. zero, since the tractor is pulling the wagon forward
According to Coulomb's law, the electrostatic force F between two charges q1q one and q2q 2 is directly proportional to the product of the charges and inversely
According to Coulomb's law, t-------------
Option (C) is correct. An alkaline battery consists of two electrodes (the anode and the cathode) separated by an alkaline electrolyte, such as KOHK O H. Oxidation and reduction reactions occur at the anode and cathode, respectively, producing a current. Thus, chemical energy is converted into electrical energy.
An alkaline battery converts which of the following forms of energy into electrical energy? Heat Kinetic Chemical Mechanical
Option (B) is correct. The frequency heard by the stationary observer depends on whether the vehicle is approaching the observer or moving away from the observer, a phenomenon known as the Doppler effect. When the vehicle is approaching the observer, the frequency heard by the observer is higher than the frequency heard by the driver. When the vehicle is moving away from the observer, the frequency heard by the observer is lower than the frequency heard by the driver.
An emergency vehicle, blowing its siren, approaches a stationary observer and then passes and moves away. Which of the following is true of the frequency of the sound of the siren heard by the stationary observer as compared with that heard by the driver? Approachin/ Moving Awayequals A.Higher/The same B.Higher/Lower C.Lower/Higher D.The sameLower
Option (A) is correct. An interstellar cloud of dust, hydrogen, helium, and other ionized gases is called a nebula. The dust is primarily composed of silicon and carbon. Some nebulae are stellar nurseries, the birthplace of stars
An immense cloud of gas (mainly hydrogen) and dust that is found in interstellar space is called A.a nebula B.a black hole C.a comet D.the asteroid belt
Option (A) is correct. BaCl2B a C l 2 is most likely to exist based on periodic trends in chemical reactivity. Barium is in group 2 in the periodic table and loses its two valence electrons to form Ba2+B a 2 positive 2 ions. Chlorine is in group 17 in the periodic table and gains an electron to form Cl-C l negative one ions. BaCl2B a C l 2 is an ionic compound composed of Ba2+B a 2 positive 2 and Cl-C l negative one ions.
Based on positions of elements in the periodic table, which of the following compounds is most likely to exist? A.BaCl2 B.KCl2 C.AlCl2
Option (D) is correct. The daily change in the position of the bean plant's leaves dependent on the time of day but independent of light is an example of circadian rhythm. The plants undergo genetically programmed physiological changes that affect the position of the leaves in a cyclic fashion over an approximately 24-hour period.
Bean plants lower their leaves in the evening and raise them to a horizontal position in the morning. The movements will continue even if the plant is kept in constant light or darkness. Such movements are referred to as A.photoperiodism B.phototropism C.morphogenesis D.circadian rhythm
Option (B) is correct. A molecule of DNA is composed of two antiparallel strands of nucleotides; the strands are held together by hydrogen bonds between complementary base pairs on the two strands. During DNA replication, the two strands separate and a new strand complementary to each template strand is synthesized by DNA polymerases. Because nucleotides containing adenine (A) must pair with nucleotides containing thymine (T) and nucleotides containing cytosine (C) must pair with nucleotides containing guanine (G), only one possible nucleotide can be added opposite the nucleotide present on the template strand. Thus each template strand dictates the sequence of the new strand with which it will bind.
DNA synthesis occurs by semiconservative replication in which each strand serves as the template for synthesis of a new strand. Which of the following characteristics of DNA is most important to this mechanism? A.DNA is composed of four different nucleotides. B.The two strands of a DNA molecule exhibit complementary base pairing. C.DNA is a helical molecule with a constant distance between each turn of the helix. D.A strand of DNAis extended only by the addition of nucleotides to the 3′ -OH deoxyribose.
Option (B) is correct. The change in internal energy of the system is equal to the energy absorbed by the system minus the energy used by the system to do work on the surroundings, or (4.8 kJ - 1.2 kJ) = 3.6 kJ.
During a chemical process, a system absorbs 4.8 kJ4 point 8 kilojoules of heat while doing 1.2 kJone point 2 kilojoules of work on the surroundings. The change in internal energy of the system is A. +4.8 kJ positive 4 point 8 kilojoules B. +3.6 kJ positive 3 point 6 kilojoules C. -1.2 kJ negative one point 2 kilojoules D. -6.0 kJ
Option (B) is correct. The seasons result from Earth's axis being tilted relative to its orbital plane. The tilt angle of 23.5 degrees23 point 5 degrees allows, at any given time during summer or winter, one hemisphere of the planet to receive more focused and concentrated exposure to the rays of the Sun. This exposure alternates as Earth revolves in its orbit around the Sun. Thus, the northern and southern hemispheres experience opposite seasons. The effect of axial tilt also influences day length and positioning of the Sun above the horizon, both of which contribute to the amount of heating of Earth and the atmosphere during a given season.
Earth's seasons in the temperate regions are caused by A.the rotation of the Sun on its axis B.the tilt of Earth on its axis as it revolves around the Sun C.changes in the distance of Earth from the Sun D.the gravitational pull of the Sun on Earth
Option (B) is correct. Ernest Rutherford published results of his gold foil experiment in 1911. A beam of alpha particles was directed at a thin sheet of gold foil. Most of the particles passed through the foil, but some were reflected or deflected, providing experimental evidence that the atom has a relatively small nucleus that contains most of the mass of the atom.
Experimental evidence supports the fact that most of the mass of an atom is contained in which of the following? a. The electron cloud b. The nucleus c. The sublevels d. The valence level
Option (C) is correct. The Opportunity Rover landed in an area where layered rocks and marble-sized concretions of hematite were visible. On Earth, hematite is a mineral that forms in the presence of water. The Spirit Rover found evidence of water in the form of the mineral goethite, which also forms in the presence of water. Later analysis of data provided by the Rover shows sulfate-rich and carbonate-rich rocks, both frequently associated with regions covered by water.
Exploration of Mars's surface by the Mars Rovers in 2004 has led to the discovery of which of the following? A.Fossilized microbial organisms B.Living, single-celled organisms C.Evidence of liquid water in the past D.Pockets of ammonia ice, which may have been deposited by comets
Option (B) is correct. The only way the couple could have a child with blood type O is for each parent to have at least one ilowercase i allele; ilowercase i is recessive to I AI Auppercase I superscript A and I BI Buppercase I superscript B. The child must receive one i allele from each parent, as blood type O requires that the individual has genotype iilowercase i, lowercase i. The woman is blood type B, so her genotype must be I BiI Biuppercase I superscript B, lowercase i. The only way this couple could have a child with blood type ABA B is if the man has the genotype I AiI Aiuppercase I superscript A, lowercase i. The two children with blood type B must have the genotype I BiI Biuppercase I superscript B, lowercase i.
IA woman with blood type B (genotype I BI BI BI Bi) has four children with a man whose blood type is unknown. Two of the children have blood type B, one has blood type O, and one has blood type ABA B. What must the blood types of the parents be? A.Woman: I BiI Bi , man: I AI AI AI A B.Woman: I BiI Bi , man: I AiI Ai C.Woman: I BI BI BI B , man: I AI BI AI B D.Woman: I BI BI BI B , man: I Ai
Option (D) is correct. Since the water is boiling, the water is at the same temperature in both the beaker and the bathtub. The heat content of a sample of a substance depends on the amount of the substance in the sample and the temperature. Since the bathtub holds more water than the beaker holds and the temperature is the same in both, the sample of boiling water in the bathtub has greater heat content than the sample in the beaker has.
If a beaker and a bathtub are each filled with pure boiling water, which of the following indicates the relative temperatures and heat content of the water in each? Temperature& Heat Content A.Higher in bathtub-Greater in bathtub B.Higher in beaker-Greater in beaker C.Same in both-Same in both D.Same in bothGreater in bathtub
Option (B) is correct. For a plane mirror, the image distance is equal to the object distance. That is, the image formed by the mirror is located the same distance behind the mirror as the object is located in front of the mirror
If a flat object is placed 3 meters in front of a plane mirror, the image will be formed a. on the surface of the mirror b. 3 meters behind the surface of the mirror c. greater than 3 meters behind the surface of the mirror d. less than 3 meters behind the surface of the mirror
Option (B) is correct. Electric current is defined as the charge per unit time passing a given point. A current of 1 ampere is equal to 1 coulomb per second. Thus a steady current of 0.1 amperezero point one ampere in 20 seconds corresponds to a total charge of 2 coulombs.
If a wire carries a steady current of 0.1 ampzero point one ampere for 20 seconds, which of the following gives the total charge passing through the wire during this time interval? 0.005 coulomb 2 coulombs 20 coulombs 200 coulombs
Option (B) is correct. The period T of a simple pendulum of length L is given by the equation T=2πLg−−√T=2πLgT equals 2 pi times the square root of the fraction L over g, where g is the acceleration due to gravity. If the length of the pendulum is doubled, then the period of the pendulum will increase by a factor of 2√2the square root of 2.
If the length of a simple pendulum is doubled, the period of the pendulum will A.increase by a factor of 2 B.increase of a factor by √2 the square root of 2 C.remain the same D.decrease by a factor of 2
Option (A) is correct. The solution process of the compound is endothermic. The thermal energy required for the process is transferred from the water, so the temperature of the water decreases.
If when a certain compound is dissolved in water, the temperature of the water decreases, the process is called A.an endothermic process B.an exothermic process C.hydration D.condensation
Option (D) is correct. Adaptive radiation is the process by which a population from an ancestral species relocates to a new environment, occupying a variety of niches. Each niche has different selective pressures, leading to the emergence of new species.
In a chain of islands, closely related bird species occupy different islands. The species share a common ancestor that inhabits the mainland. Which of the following was the most likely mechanism of speciation? A.Coevolution B.Gene flow C.Spatial isolation D.Adaptive radiation
Option (A) is correct. Since cold air is more dense than warm air, convection currents will develop, with warmer air rising to the ceiling and cooler air dropping toward the floor. When the ceiling is high, there will be a greater temperature difference between ceiling and floor, thus making it more difficult to make people comfortable.
In cold weather, it is more difficult to make people comfortable in a room with a high ceiling than in a room with a low ceiling primarily because a. cold air is more dense than warm air b. humid air is more dense than dry air c. convection currents do not occur in rooms with a high ceiling d. evaporation occurs more rapidly in a room with a high ceiling than in a room with a low ceiling
Option (D) is correct. Active transport refers to moving a substance such as an ion against its gradient (often a concentration gradient), from lower to higher. This requires a source of energy. In eukaryotic cells, as ATPA T P is hydrolyzed to ADP + PiA D P plus P subscript i energy is released. Cells obtain the energy to initially synthesize ATPA T P through metabolism of foods such as sugar. ATPA T P is formed through the pathways of glycolysis and the Krebs cycle but especially as a consequence of energy transfers during redox reactions along electron transport chains in the mitochondria.
In eukaryotic cells, which of the following provides energy for the active transport of ions across the plasma membrane? A.Nuclei produce mRNAm R N A to provide energy for active transport. B.Vacuoles store fat to provide energy for active transport. C.Chloroplasts fix nitrogen to synthesize ATPA T P. D.Mitochondria use the energy in sugars to synthesize ATPA T P.
Option (A) is correct. Endothermic animals are those animals that are warmed by heat generated by their own metabolism. They can also lose heat by several mechanisms, one of which is the dilation of blood vessels of the skin. Dilation permits greater blood flow through the vessels and facilitates cooling of heated blood as heat is lost to the environment.
In order for endothermic animals to maintain homeostasis of body temperature, the body will prevent above-normal body temperatures by A.directing blood vessels of the skin to dilate B.directing blood vessels of the skin to constrict C.directing the erector pili muscles in the skin to contract and raise the hair D.sending nerve impulses to skeletal muscles to cause shivering
Option (D) is correct. Osmosis refers to the passive movement of water into a region of higher solute concentration from a region of lower solute concentration. The concentration of dissolved minerals inside the root hairs is much higher than the concentration outside the root hairs, in the soil, and similarly the concentration of water is higher in the soil than in the root hairs, so water enters the large surface area of the root hairs by osmosis.
In the root system of a vascular plant, the movement of water from the soil into the plant's root cells occurs by A.capillarity B.translocation C.turgor pressure D.osmosis
Option (B) is correct. Of the four types of electromagnetic radiation listed, the most energetic photons are found in gamma rays, the least energetic photons are found in infrared radiation, and ultraviolet photons are more energetic than visible light photons.
In which of the following are the types of electromagnetic radiation listed in order of increasing energy? a. Visible < infrared < gamma rays < ultraviolet b. Infrared < visible < ultraviolet < gamma rays c. Gamma rays < visible < infrared < ultraviolet d. Ultraviolet < visible < infrared < gamma rays
Option (C) is correct. In 1609, Johannes Kepler published what is now known as Kepler's first law of planetary motion. Kepler, a mathematician, asserted that observations of the movements of Mars were consistent with the planet having an elliptical orbit with the Sun as one of the focal points. Kepler's law refined the Copernican model of the solar system.
Johannes Kepler's greatest contribution to science was that he proposed the law of universal gravitation discovered the first radioactive element described the orbits of the planets as ellipses developed the microscope
Option (B) is correct. The source of almost all freshwater on Earth is precipitation from the atmosphere, which, in turn, was originally from ocean water that evaporated. When ocean water evaporates, the solids are left behind and only freshwater is transferred to the atmosphere. This allows land-based water, including streams, rivers, lakes, and ground water, to be considered fresh.
Most of the water on Earth is in the ocean, but freshwater occurs in rivers, lakes, glaciers, and groundwater. Which of the following best helps explain why freshwater exists on Earth? A.Salt water is purified as it flows through the ground. B.Water evaporation off the surface of the oceans removes water and leaves salts behind. C.Circulation of seawater through the midocean ridges produces freshwater. D.Salts dissolved in rivers and lakes settle to the bottom with time.
Option (D) is correct. Night vision devices based on thermal imaging, such as infrared cameras, detect thermal radiation that is in infrared range of the electromagnetic spectrum.
Night vision devices that are based on thermal imaging detect which of the following? A.Carbon dioxide B.Electrical conductivity C.Sound waves D.Infrared radiation
Option (A) is correct. It is estimated that at least 75 percent of all living species are insects. The number of insect species alive today is estimated to be at least two million and may be many times greater. More than 750,000 of the species have been described. Insects may be found in all environments, although very few are found in the oceans. Insects probably have the largest biomass of all terrestrial animals.
Of the following animal classes, which includes the greatest number of species? A.Insecta B.Amphibia C.Reptilia D.Mammalia
Option (B) is correct. Of the elements listed, only BiB i is a metal. Metallic character decreases across the rows (periods) and increases down the columns (groups) of the periodic table.
Of the following elements, which is the most metallic? A.P B.Bi C.S D.Si
Option (C) is correct. Oxygen, at 46.6 percent and silicon, at 27.7 percent, comprise nearly three-fourths of the composition of the rocks that make up Earth's crust. Given the abundance of these elements, it is not surprising that the most abundant minerals in Earth's crust are in the silicate family, which build upon the silicon tetrahedron (four oxygen atoms and one silicon atom bonded together). Although hydrogen is found in water, and is the most abundant element in the universe, it is not common in crustal rocks.
Of the following elements, which two are most abundant in Earth's crust? A.Silver and copper B.Hydrogen and iron C.Silicon and oxygen D.Oxygen and hydrogen
Option (D) is correct. Primary consumers eat producers, which are autotrophs such as plants, algae, and cyanobacteria. Hence, grasshoppers that eat plants are primary consumers.
Of the following organisms, which are primary consumers in an ecosystem? A.Algae B.Cyanobacteria C.Frogs D.Grasshoppers
Option (D) is correct. Ferromagnetic substances will be most strongly attracted to a magnet. Of the four elements listed, only iron is ferromagnetic.
Of the following substances, which is most strongly attracted to a magnet? A.Aluminum B.Magnesium C.Gold D.Iron
Option (A) is correct. Hydrogen is a nonpolar molecule. Because each hydrogen atom in the molecule has only one electron shell, it is less polarizable than other diatomic molecules. As a result, it has relatively weak London dispersion forces only and therefore a low boiling point.
Of the following, which has the lowest normal boiling point? A.H2 B.I2 C.H2O D.NH3
Option (C) is correct. Absolute age of a fossil is determined through radioactive dating. If there is an isotope inside a mineral in a rock that is radioactive, it will break down naturally into a lighter element called a decay, or daughter, product. This process occurs at a predictable rate, referred to as half-life, which is the time required for half an element's atoms (the parent) in a sample to change to the decay (daughter) product. Examining the decay-product (daughter-parent) ratio can be used to determine how old an object is.
Of the following, which is the best method to determine the exact age of a particular fossilized animal? A.Noting how closely the fossil's shape resembles that of its relatives living today B.Noting what rock type the fossil was found in C.Obtaining a radioactively determined date from rock stratigraphically near the fossil D.Applying the principle of faunal succession, which places fossils in order of age
Option (C) is correct. In both the Bohr and quantum mechanical models, electrons are only in certain allowed energy states.
One similarity between the Bohr and quantum mechanical models of the atom is that electrons a. are embedded in the nucleus b. revolve around the nucleus in circular orbits c. are only in certain allowed energy states d. behave as particles and not as waves
Option (C) is correct. Planets are bodies that orbit stars, however they do not give off their own light. Stars generate their own light and energy via a process known as nuclear fusion, when fast-moving hydrogen nuclei are smashed together to form helium. This fusion process produces enough energy for stars to shine. Planets are visible only because of the sunlight they reflect.
One way in which stars differ from planets is that stars A.can be seen during the night B.are located in galaxies C.produce their own light D.occupy fixed positions in the sky
Option (C) is correct. The term "angiosperm" refers to a plant that produces seeds within an enclosure (the fruit) and is commonly called a flowering plant. Conifers are a type of gymnosperm, a group that reproduces by making "naked" unenclosed seeds but does not flower. Bryophytes, a collective term for nonvascular plants, reproduce by producing spores. Similarly, ferns reproduce only through the production of spores.
Plants that reproduce by making flowers and seeds are classified as A.conifers B.bryophytes C.angiosperms D.ferns
Option (C) is correct. The skin of some amphibians is thin and membranous, which allows the free diffusion of the gases O2 and CO2 down the concentration gradients between the blood vessels under the skin and the surroundings. When completely submerged in water, all of the gas exchange of some amphibians occurs through the skin. When out of the water, mucus glands keep the skin moist, which facilitates gas exchange with the air.
Since the lungs in many adult amphibians are small or even absent, upon which of the following do they mainly depend for gas exchange? A.Alveoli B.Tracheae C.Skin D.Air bladders
ption (D) is correct. A transformer is a device which inductively couples two AC circuits and can be used to step up voltage or step down voltage.
The device shown above has an input voltage of 25.0 V25 point zero volts and an output voltage of 50.0 V50 point zero volts. The device is which of the following? Resistor Capacitor Battery Transformer
Option (C) is correct. A wavelength is the distance between wave crests for a traveling wave, or twice the distance between adjacent nodes for a standing wave. Thus the wavelength is 1.000 mone point zero zero zero meter. The speed of the wave is equal to the frequency times the wavelength: v=fλv=fλ = 100.0 Hz × 1.000 m = 100.0 m/sv equals f times lambda, equals 100 point zero Hertz, times one point zero zero zero meter, which is equal to 100 point zero meters per second.
The distance between the adjacent nodes of a one-dimensional standing wave is 0.500 mzero point five zero zero meter. If the frequency of the wave is 100.0 Hz100 point zero hertz, then the speed of the wave is 25.0 m/s (25 point zero meters per second) 50.0 m/s (50 point zero meters per second 100.0 m/s) 100 point zero meters per second 200.0 m/s
Option (D) is correct. The chemical properties of the elements in the first column are largely determined by their electron configurations. Elements in group 1 have one electron in their valence shell and have similar chemical properties.
The elements in the first column in the periodic table have similar chemical properties because they have A.similar densities B.the same atomic masses C.the same number of protons in their atoms D.the same number of outer electrons
The law of conservation of energy states that the total energy of an isolated system remains constant.
The law of conservation of energy states that ____________________________________________
Option (B) is correct. The troposphere is the lowest layer of Earth's atmosphere. It extends to an average altitude of approximately 17 km (11 mi). The troposphere is where most weather phenomena occur.
The lowest layer of the atmosphere is called the A.thermosphere B.troposphere C.mesosphere D.stratosphere
The net ionic reaction shows only the ions that react to form the precipitate AgClA g C l.
The net ionic reaction shows only the ions that react to form the precipitate___________________
Option (B) is correct. The molar mass of MgM g is 24.3 g/mol4 point 3 grams per mole; therefore, 48.6 g of Mg48 point six grams of M g contain 2 moles of MgM g atoms.
The number of moles of atoms in 48.6 g of Mg48 point six grams of M g is A. 0.5 B. 2 C. 6.02 × 1023 D.12.04 × 1023
Option (D) is correct.
The pHp H of a 0.001 M KOHzero point zero zero one molar K O H solution is approximately A.1 B.3 C.7 D.11
Option (A) is correct. The epicenter of an earthquake is the point on Earth's surface directly above the focus (or hypocenter), which is the point where rupture along a fault occurs.
The position on Earth's surface that lies directly above the point inside Earth where an earthquake originates is known as the A.epicenter B.focus C.fault D.plate
Option (B) is correct. The inner bark contains the phloem, which is living vascular tissue that carries sugar and other organic nutrients from the leaves to other parts of the plant, including the roots. Removing the bark will prevent the flow of sugar to the roots and eventually kill the tree.
The primary reason that stripping the outer and inner bark from the circumference of a tree will eventually kill the tree is that removal of the bark A.makes the tree susceptible to desiccation B.prevents the transport of sugar to the roots C.compromises the structural support of the tree D.prevents the transport of water from the roots
Option (A) is correct. Translation refers to the synthesis of proteins based on codons, or sequential ribonucleotide triplets, present in an mRNAm R N A. A ribosome binds to an initiation codon of an mRNAm R N A, and tRNAst R N As, carrying individual amino acids as dictated by the codon sequence, bind to sequential codons in the mRNAm R N A. The ribosome forms peptide bonds between the amino acids, and the amino acids are released from the tRNAst R N As, which then dissociate from the mRNAm R N A and the ribosome.
The process of translation uses the genetic code in messenger RNAR N A in the synthesis of which of the following? A.Proteins B.Lipids C.DNA D N A D.Carbohydrates
Option (C) is correct. At 40°C, 78 of KClK C l is dissolved in 200 g H 2 O to produce a saturated solution. The remaining 4 g4 grams of undissolved solid is in equilibrium with the saturated solution.
The solubility of KCl at 40°C is 39 g in 100 g of waterK C l at 40 degrees Celsius is 39 grams in 100 grams of water. If 82 g of KCl82 grams of K C l is added to 200 g200 grams of water at 40°C40 degrees Celsius, which of the following is true at equilibrium? A.All of the KClK C l is dissolved, and the solution is saturated. B.All of the KClK C l is dissolved, and the solution is unsaturated. C.Most, but not all, of the KClK C l is dissolved, and the solution is saturated. D.Most, but not all, of the KClK C l is dissolved, and the solution is unsaturated.
Option (C) is correct. Taxis is a response toward or away from a stimulus. The swimming of trout into a water current is referred to as positive rheotaxis. The behavior points the fish in the direction from which most food appears and keeps the fish from being swept away. The fish detect the current and respond to it through the lateral line system, a mechanosensory system distributed superficially on the skin surface and in fluid-filled canals just under the skin on the head and body of the fish.
Trout automatically swim or orient themselves in an upstream direction that keeps them from being swept away. This behavior is an example of A.migration B.kinesis C.taxis D.learning
Option (B) is correct. The two astronauts are initially at rest, which means that the initial total momentum of the two astronauts is equal to zero. In the absence of any net external forces, linear momentum is conserved. Thus the total momentum of the two astronauts after they push each other apart must be equal to zero. That means that the two astronauts will move apart in opposite directions and that the speed of the heavier astronaut can be found using the equation mheavyvheavy=mlightvlightmheavyvheavy=mlightvlightmass of heavy astronaut, times speed of heavy astronaut, equals mass of light astronaut, times speed of light astronaut, which gives = (60 kg × 12 m/s)/80 kg = 9 m/sspeed of heavy astronaut, equals 60 kilograms, times 12 meters per second, divided by 80 kilograms, which is equal to 9 meters per second.
Two astronauts, of masses 60 kg60 kilograms and 80 kg80 kilograms, are initially at rest in outer space. They push each other apart. If the speed of the lighter astronaut is 12 m/s12 meters per second, what is the speed of the heavier astronaut? a. 4 m/s ( 4 meters per second) b. 9 m/s ( 9 meters per second) c. 12 m/s ( 12 meters per second) d. 16 m/s
Option (D) is correct. Carrying capacity is defined as the maximum population size that a particular environment can support based on available resources, including food, shelter, and sites in which to nest or hide from predators. If the population is at one-half the carrying capacity of the habitat, the population will most likely continue to increase in size.
Under which of the following circumstances would a population of animal species be expected to increase at the greatest rate? A.New predators are introduced into its habitat. B.The habitat is experiencing a prolonged drought. C.The population has reached its carrying capacity. D.The population size equals one-half the carrying capacity of the habitat.
Option (A) is correct. Upwelling currents occur when winds blowing across the ocean surface push water away from an area. When this occurs, water rises from beneath the surface to replace the diverging surface water. Subsurface water that rises to the surface as a result of upwelling is typically colder, rich in nutrients, and biologically productive. Therefore, good fishing grounds are found where upwelling is common. The west coast of South America is one such area.
Upwelling currents along the west coast of South America are characterized by A.cold, nutrient-rich water B.warm, nutrient-rich water C.cold, nutrient-poor water D.warm, nutrient-poor water
Option (D) is correct. According to the law of conservation of matter, the total mass of the products is equal to the total mass of the reactants consumed in the reaction. The law of conservation of energy states that the total energy of an isolated system remains constant. During the burning of a log, some chemical energy is converted to thermal energy and light energy and the total energy of the system is constant.
When a log burns in a fireplace, producing ash and smoke, which of the following is true? A.Energy is created but matter is conserved. B.Energy is created and matter is destroyed. C.Energy is conserved but matter is destroyed. D.Energy and matter are both conserved.
Option (D) is correct. Entropy always decreases when a substance undergoes a phase change from a gas to a liquid. Mass and temperature are unchanged, and density generally increases, with a few exceptions.
When a substance undergoes a phase change from a gas to liquid at its boiling point, which of the following properties of the substance always decreases? Density Mass Temperature Entropy
Option (B) is correct. Homologous structures are structures of different species that have some similarity because they are derived from a common ancestor. A bat and a human share a common vertebrate ancestor.
When the bones of the human arm and the bones of a bat wing are compared, many similarities are observed. These similarities are examples of A.vestigial organs B.homologous structures C.embryonic similarity D.convergent evolution
Option (C) is correct. Mid-ocean ridges are features associated with divergent plate boundaries, where two plates are separating and moving away from each other. At these types of boundaries, magma from the asthenosphere rises up and forces the two plates apart. When the magma reaches the surface, whether on land or on the ocean floor, it cools and hardens to form new crustal rock. Older rocks would be found farther away from the mid-ocean ridge as the new magma rises and the two plates continue diverging.
Where in the ocean basins would the youngest rock of the ocean floor be found? A.Trenches found in the deep ocean B.Abyssal plains C.Mid-ocean ridges D.Continental shelves
Options (A), (C), and (D) are correct. The water table is the surface of groundwater. When significant amounts of water are removed from an aquifer, the water table is lowered. Removing water from pore spaces in the rock or sediment that make up the aquifer reduces the support given to the overlying material and can cause the ground to subside. In coastal areas, there is a wedge of denser salt water beneath the freshwater. When freshwater is withdrawn, the lower boundary of freshwater rises and salt water moves in to take its place. There is no reason for withdrawal of water from an aquifer to increase the recharge area.
Which THREE of the following are likely to result from excessive withdrawal of groundwater from an aquifer? A.The water table is lowered. B.The recharge area increases. C.There is saltwater intrusion of the aquifer if it is near the coast. D.The ground subsides.
Options (A) and (B) are correct. Insulin is a peptide hormone secreted by beta cells of the pancreas. It plays a role in regulating blood sugar levels and the rate of fat metabolism.
Which TWO of the following are true about insulin? A.It is secreted by cells of the pancreas. B.It plays a role in regulating blood sugar levels. C.It acts as an enzyme in the initial step of the digestion of fats. D.It is a steroid hormone.
Options (B) and (D) are correct. Chemical weathering occurs when water, gas, and acid interact with minerals in rocks, leading to various chemical reactions that change the rocks' composition. Dissolution occurs when atmospheric carbon dioxide dissolves in rainwater, producing a weak acid known as carbonic acid. Carbonic acid is effective at dissolving rocks, especially those containing calcite, such as limestone and marble. Oxidation occurs when atmospheric oxygen reacts with various metals in minerals to create a new oxide mineral. Rusting is the better-known term for this process.
Which TWO of the following are types of chemical weathering? A.Abrasion B.Dissolution C.Exfoliation D.Oxidation
Options (A) and (C) are correct. The solubility of a gas in a liquid is affected by the temperature of the liquid and the pressure of the gas above the liquid. Decreasing the temperature of the water and increasing the pressure of carbon dioxide above the water increases the solubility of the carbon dioxide in the water.
Which TWO of the following increase the solubility of carbon dioxide in water? A.Decreasing the temperature of the water B.Increasing the temperature of the water C.Increasing the pressure of carbon dioxide above the water D.Stirring the water while adding carbon dioxide
(C) is correct. Valence electrons of metals are delocalized and held loosely in a crystal lattice of positive ions. The mobility of the electrons accounts for the electrical conductivity of metals.
Which of the following best accounts for the fact that metals are good conductors of electricity? A.Valence electrons are transferred from one atom to another to form positive and negative ions. B.Valence electrons are shared between neighboring atoms only. C.Valence electrons are delocalized in a crystal lattice of positive ions. D.Polar covalent bonds form between the atoms.
ption (D) is correct. When the Sun, Earth, and Moon are in alignment (a condition known as syzygy), the tidal force due to the Sun is increased, which reinforces the tidal force produced by the Moon. The tide's range is then at its maximum range, called spring tide.
Which of the following best describes the effect on the tides when the Sun, Earth, and Moon are in alignment? A.There are no tides, because the gravitational forces due to the Sun and the Moon cancel each other out. B.The difference between high and low tides does not change over the 28-day lunar cycle. C.The difference between high and low tides is relatively small. D.The difference between high and low tides is relatively large
Option (D) is correct. In the hierarchy of organism classification, phyla (the plural of phylum) include classes, which include orders, which include families.
Which of the following categories used to classify biological organisms includes the other three categories? A.Class B.Order C.Family D.Phylum
Option (D) is correct. A hypothesis is a tentative explanation for a set of observations. Further experiments are conducted to test the validity of the hypothesis. If the hypothesis proves valid following many experimental tests over an extended period of time, it may be referred to as a theory
Which of the following characteristics is most important in demonstrating that a hypothesis should be called a theory? A.It interprets an observation. B.It states a conclusion supported by an experiment. C.It summarizes the most recent work of a scientist. D.It provides an explanation for the results of many experiments.
Option (A) is correct. In an experiment, only one factor at a time should be varied. This factor is called the manipulated or independent variable. The responding or dependent variable will be measured and recorded.
Which of the following guidelines should be used when collecting data during an experiment? A.Vary only one factor at a time when studying how a system responds. B.Take all measurements at the same time. C.Make sure that the measurements agree with the hypothesis that motivated the experiment. D.Make sure the measurements form a straight line when plotted on a graph.
Option (C) is correct. Lines on a weather map connecting points of equal air pressure are referred to as isobars. The word isobar means equal (iso-) weight (-bar). Distribution of isobars is closely related to wind magnitude and direction and can be used to predict future weather patterns.
Which of the following is a line on a weather map that connects points of equal pressure? A.Thermocline B.Isotherm C.Isobar D.Streamline
Option (D) is correct. The Calvin cycle fixes CO2C O 2 to organic molecules to synthesize the 3-carbon sugar glyceraldehyde 3-phosphate. The products of the light reactions, ATPA T P and NADPH N A D P H, are used during the Calvin cycle as a source of energy and electrons, respectively.
Which of the following is a product of the Calvin cycle of photosynthesis? A.Oxygen B.ATP C.NADPH D.Sugar
Option (A) is correct. Concentrated acid should be added to water. (B) is unsafe because alcohol is flammable, and (C) is a poor procedure because the volatile liquids will evaporate. (D) is not a safe practice, since many chemicals will contaminate waste water, no matter how much water is added, and because some chemicals that may become mixed can react with each other and produce harmful products, including gases that can disperse into the laboratory.
Which of the following is a safe laboratory procedure? A.Preparing a dilute acid solution by adding a small amount of concentrated acid to water in a flask B.Using a flame to heat an open beaker of alcohol C.Storing volatile liquids in containers with loose lids D.Flushing all waste chemicals down the laboratory sink with large amounts of water
Option (A) is correct. A parasitic relationship is one in which one organism benefits and the other is harmed. The ticks obtain nourishment from the blood they suck from the deer. The deer may be harmed if it loses too much blood, if too many ticks are attached, or if it contracts an infection from the ticks.
Which of the following is an example of a parasitic relationship? A.Ticks attached to a white-tailed deer B.Nitrogen-fixing bacteria living in nodules on the roots of a bean plant C.Protozoans living in the intestine of an adult termite D.Algae living in the cytoplasm of an amoeba
Option (C) is correct. One gram is equal to 1,000 milligrams, so 1 × 10-3 g × (1,000 mg/g) = 1 milligram (0.001 gram)one times 10 to the negative 3 grams, times 1,000 milligrams per gram, equals one milligram zero point zero zero one gram.
Which of the following is equivalent to 1 × 10-3 gone times 10 to the negative 3 grams? A.0.0001 B.1 kilogram C.1 milligram D.100 micrograms
Option (B) is correct. The polyatomic anion nitrate (NO3-)N O 3 negative one ion has a charge of -1negative one. Therefore, copper has a charge of +2positive 2, designated by the Roman numeral IIRoman numeral 2.
Which of the following is the correct name for Cu(NO3)2C u, open parenthesis N O 3 close parenthesis, 2 ? A. A: Copper dinitrate B. B: Copper(IIRoman numeral 2) nitrate C. C: Copper nitrogen trioxide D. D: Cuprous nitrogen trioxide
Option (D) is correct. The atomic number for TiT i, titanium, is 22; therefore a neutral atom of TiT i has 22 electrons and, using the Aufbau principle, the ground state electron configuration is 1s22s22p63s23p64s23d21 s
Which of the following is the ground state electron configuration for TiT i? A.1s22s22p23s23p64s21s22s22p23s23p64s2 1 s 2, 2 s 2, 2 p 2, 3 s 2, 3 p 6, 4 s 2 B.1s22s22p63s23p64s24p21s22s22p63s23p64s24p2 1 s 2, 2 s 2, 2 p 6, 3 s 2, 3 p 6, 4 s 2, 4 p 2 C. 1s22s22p63s23p63d41s22s22p63s23p63d4 1 s 2, 2 s 2, 2 p 6, 3 s 2, 3 p 6, 3 d 4 D.1s22s22p63s23p64s23d2
Option (C) is correct. The most common cause of Down syndrome is trisomy 21, or three copies of chromosome 21 in every cell. A gamete should contain only one copy of every chromosome, so that a zygote contains two copies of every chromosome. If the homologous pairs of chromosome 21 do not separate during meiosis I or if the chromosome 21 chromatids do not separate during meiosis II, gametes will form with two copies of chromosome 21. When such a gamete fuses with a gamete containing the normal one copy of chromosome 21, the zygote will contain three copies of the chromosome. The consequent overproduction of chromosome 21-encoded proteins causes Down syndrome.
Which of the following is the most likely cause of Down syndrome? A.The inability of cells to produce functional mRNAm R N A molecules B.The inheritance of a dominant allele for the syndrome from one of the parents C.The nondisjunction of chromosome 21 during meiosis D.The failure of chromosome 21 to replicate before the start of meiosis
Option (D) is correct. The term "continental shelf" generally means the part of the continental margin that is between the shoreline and the shelf break, or where there is very little to no noticeable slope. The continental shelf can be virtually absent or it can extend hundreds of miles. Typical water depths along the continental shelf are between 100 and 200 meters. The continental shelf often contains the highest amount of benthic life (animals and plants that live on the ocean floor).
Which of the following is true of a continental shelf? A.It usually extends a mile or less from the shore. B.It supports little biodiversity. C.The water above it is typically more than 10 km10 kilometers deep. D.It is the undersea extension of a continent.
Option (B) is correct. One of the properties that distinguishes the mineral calcite from other minerals is its reactivity with acid. When a drop of dilute hydrochloric acid is placed on calcite, the mineral will fizz, or effervesce, indicating carbon dioxide is released during the chemical reaction. Quartz, feldspar, and magnetite do not react in the presence of acid.
Which of the following minerals effervesces (to give off bubbles of gas, as fermenting liquors) when placed in an acid solution? A.Quartz B.Calcite C.Feldspar D.Magnetite
Option (A) is correct. The diaphragm is a rotating disk under the stage that is used to control the intensity and size of the cone of light directed upward to the slide.
Which of the following parts of a compound microscope would be used to regulate the amount of light transmitted through the specimen on a slide? Diaphragm Nosepiece Fine adjustment knob Coarse adjustment knob
Option (A) is correct. A planet's revolution is the amount of time it takes to orbit the Sun. Kepler's third law of planetary motion states that planets closer to the Sun experience shorter orbital periods. The closest planet to the Sun is Mercury, which has an orbital period of approximately 88 Earth days, the shortest of all planets in the solar system.
Which of the following planets has the shortest period of revolution around the Sun? A.Mercury B.Earth C.Jupiter D.Neptune
Option (C) is correct. Malleability is the ability of a substance to be hammered into thin sheets and is a physical property that characterizes metals.
Which of the following properties of matter refers to the ability to be hammered into thin sheets? Density Tensile strength Malleability Ductility
Option (D) is correct. The region of Earth receiving the Sun's most focused and concentrated rays is the equator, where air is heated and rises, leaving behind areas of low pressure. Surface trade winds from the tropics also converge near the equator, and as they are heated, the air rises. This means there are no steady surface winds at the equator, a region sometimes called the doldrums.
Which of the following statements best describes the global wind pattern at the equator? A.Strong, steady winds moving toward the North Pole B.Strong, steady winds moving toward the South Pole C.Strong, steady winds moving from east to west D.Calm surface winds
Option (C) is correct. The new moon phase occurs when Earth, the Moon, and the Sun are approximately aligned, with the Moon passing between Earth and the Sun. Because of this arrangement, observers on Earth cannot see the lit portion of the Moon, which is facing away from Earth, in the direction of the Sun. The new moon lasts for approximately two days during the lunar cycle of phases.
Which of the following statements best describes the view of the Moon as seen from Earth during the new moon phase? A.The right half of the Moon appears lit, with the lit part growing larger on successive days. B.The left half of the Moon appears lit, with the lit part growing smaller on successive days. C.The lit side of the Moon faces away from Earth, causing the Moon to appear totally dark. D.The light reflecting off Earth's surface illuminates the entire surface of the Moon.
ption (B) is correct. James Hutton's concept of uniformitarianism states that all natural processes that affect the Earth's crust, such as erosion, deposition, volcanic eruptions, faulting, and glaciation, operate with the same intensity and under the same set of constraints now as in the geologic past. Hutton's concept is often rephrased as "The present is the key to the past."
Which of the following statements best summarizes Hutton's geological principle of uniformitarianism? A.The rate of deposition of sediment is nearly the same around the world. B.Present physical laws are the key to the past. C.The composition of Earth's surface is nearly the same everywhere. D.Magnetic materials are distributed nearly uniformly over Earth.
Option (A) is correct. Nicolaus Steno, a Danish geologist, observed changes in a sequence of rock layers that became known as the law (or principle) of superposition. The law states that in a sequence of sedimentary rock layers, each layer of rock is older than the layer above it and younger than the layer below it. Superposition also can be applied to geologic events on Earth's surface, such as lava flows and ash layers from volcanic eruptions.
Which of the following states the law of superposition? A.In an undisturbed section of strata, older rocks are found in lower positions. B.In an undisturbed section of strata, younger rocks are found in lower positions. C.Each section of strata must be compared to the other sections to establish relative age. D.The position of each strata cannot indicate relative age.
Option (A) is correct. Propanol can form hydrogen bonds with water, and therefore is completely miscible (soluble in all proportions) with water.
Which of the following substances is highly soluble in water? A.Propanol, CH3CH2CH2OH B.Benzene, C6H6 C.Chloroform, CHCl3 D.Hexane, C6H14
ption (B) is correct. Lipids have more energy content per gram than nucleic acids, carbohydrates, and proteins have. As lipids are metabolized, they undergo exothermic chemical reactions in which energy is required to break bonds in the lipids, but a larger amount of energy is released as new bonds are formed in the products.
Which of the following types of biological molecules contain the most energy per gram? A.Nucleic acids B.Lipids C.Carbohydrates D.Proteins
Option (B) is correct. The addition of water from rainfall adds weight to a slope and reduces friction, making the slope more susceptible to failure. Building houses at the top of a slope can add weight to slope materials, which leads to a greater driving force. Steeper slopes also have more potential for slope failure. Planting vegetation helps to stabilize slopes because roots hold soil and loose rock together. Also, plants reduce ground moisture by absorbing water from the soil.
Which of the following will decrease the likelihood of mass wasting occurring on a hillside? A.Experiencing frequent, heavy rainstorms B.Planting vegetation on the hillside C.Increasing the slope of the hillside D.Building houses near the top of the hillside
Option (A) is correct. The concentration of the solution that results from adding 250 mL of 2.0 M HCl250 milliliters of 2 point zero molar H C l to 750 mL750 milliliters of water is 0.50 Mzero point five zero molar. In 250 mL of 2.0 M HCl250 milliliters
Which of the following will result in a solution of 0.50 M HClzero point five zero molar H C l ? 250 mL250 milliliters of 2.0 M HCl2 point zero molar H C l added to 750 mL H2OA: 750 milliliters H 2 O 500 mL500 milliliters of 1.0 M HClone point zero molar H C l added to 1,000 mL H2OB: 1,000 milliliters H 2 O 100 mL of 0.50 M HCl100 milliliters of zero point five zero molar H C l added to 900 mL H2OC: 900 milliliters H 2 O 200 mL of 0.10 M HCl200 milliliters of zero point one zero molar H C l added to 1,000 mL H2OD: 1,000 milliliters H 2 O
Option (D) is correct. A common characteristic of tumor cells is that they divide more rapidly than normal cells. This is because a DNAD N A mutation shortens the length of time the cells spend in interphase, and particularly in the G1G one phase of interphase. In normal cells, the p53p 53 gene is activated when a DNAD N A mutation is detected, which is why the gene is referred to as a tumor-suppressor gene. The protein encoded by the p53p 53 gene causes production of another protein that blocks the interaction of S cyclins with cyclin-dependent kinases, an interaction that is required for DNAD N A replication and ultimately cell division. If the p53p 53 gene is mutated, the interaction of S cyclins with cyclin-dependent kinases cannot be blocked and the abnormal cells will continue to replicate their mutated DNAD N A and to divide.
p53p 53 is a tumor-suppressor gene that helps to control cell division and is often mutated in certain skin cancers. Which of the following is most likely true of skin cells with a p53p 53 mutation? A.The cells divide by meiosis instead of mitosis. B.The cells skip all stages of interphase and go from one division to the next. C.The number of chromosomes in each new generation is twice that of the previous generation. D.The cell cycle is shorter in length than in normal skin cells.
Options (A), (C), and (D) are correct. A simple machine does make work easier (e.g., by reducing the force that has to be exerted to perform a task), and a simple machine can change the magnitude or direction of a force. The mechanical advantage of a simple machine is defined as the amount by which the machine multiplies the input force and is essentially a measure of how much effort is saved by using the machine. A simple machine never changes the total amount of work required to perform a task; the total work done is the same.
rue statements about simple machines include which THREE of the following? A.A simple machine makes the work required to perform a task easier. B.A simple machine reduces the total amount of work required to perform a task. C.A simple machine can change the magnitude or direction of a force. D.The mechanical advantage of a simple machine is the amount by which the machine multiplies the input force.
Option (B) is correct. Volcanic tephra is solid material that is ejected from a volcano during an eruption. Volcanic ash is the smallest of the tephra, and consists of fine (less than 2 mm2 millimeters across) pieces of volcanic rock and glass. Ash can be ejected at enormous vertical and lateral distances from a volcano during an eruption, and can sometimes remain in the atmosphere for several years. The explosivity of an eruption often depends on the temperature and the amount of water vapor present in the exploding magma.
volcanic ash ejected from an erupting volcano is composed mostly of which of the following? A.Burned trees and other fragments of plant material destroyed by the eruption B.Very small fragments of rocks, minerals, and volcanic glass C.Water vapor and liquid water D.Pure carbon
(C) is correct. At temperatures greater than 200 K200 kelvins (T > 200 KT is greater than 200 kelvins), TΔS > 20,000 JTemperature times change in entropy is greater than 20,000 joules and ΔG < 0.change in Gibbs energy is less than zero If ΔG < 0change in Gibbs energy is less than zero, a reaction is spontaneous.
ΔG = ΔH − TΔS Change in Gibbs energy equals change in enthalpy minus temperature times change in entropy The change in Gibbs energy for a reaction at constant temperature is given by the equation above. For an endothermic reaction with ΔH = +20,000 Jchange in enthalpy equals positive 20,000 joules and ΔS = +100 J/Kchange in entropy equals positive 100 joules per kelvin, which of the following is true about the reaction? a. It is never spontaneous. b. It is always spontaneous at any temperature. c. It is spontaneous at temperatures above 200 K200 kelvins only. d. It is spontaneous at temperatures below 200 K200 kelvins only.
