questions stringlengths 37 1.22k | reasoning stringlengths 0 3.56k ⌀ | answers stringlengths 4 138 |
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How many valence electrons does helium have?
Here are the choices:
A. two
B. six
C. Five
D. three | Helium may seem to be an exception, since it has only two valence electrons. This has to do with the fact that the n = 1 energy level has one s orbital and no p orbitals. As a result, the first energy level can be completely filled by just two electrons. It is the presence of a filled valence shell that gives noble gases their unusual stability, not anything intrinsic about the number 8. In addition to helium, the first few elements such as lithium, beryllium, and boron, have a particularly stable configuration with a pair of valence electrons rather that an octet. | A: two. |
What is continuously changing within a circuit in an analog signal?
Here are the choices:
A. voltage
B. frequency
C. energy
D. amplitude | An analog signal consists of continuously changing voltage in a circuit. For example, microphones encode sounds as analog signals. | A: voltage. |
What is made and stored primarily in the cells of the liver and muscles?
Here are the choices:
A. oxygen
B. glycogen
C. carbon dioxide
D. glucose | Glycogen is an even more highly branched polysaccharide of glucose monomers that serves a function of energy storage in animals. Glycogen is made and stored primarily in the cells of the liver and muscles. | B: glycogen. |
Electromagnetic waves vary in wavelength and in what property, which is lower in waves of longer wavelengths?
Here are the choices:
A. frequency
B. resonance
C. size
D. density | Electromagnetic waves vary in wavelength and frequency. Longer wavelength electromagnetic waves have lower frequencies, and shorter wavelength waves have higher frequencies. Higher frequency waves have more energy. | A: frequency. |
In the case of transverse waves, the movement of the medium is perpendicular to the direction of the what?
Here are the choices:
A. energy movement
B. friction movement
C. pressure movement
D. fuel movement | In all types of mechanical waves, energy moves from one place to another while the media carrying the wave only vibrates back and forth in position. One type of mechanical wave is the transverse wave . In the case of transverse waves, the movement of the medium is perpendicular to the direction of the energy movement. | A: energy movement. |
Inserting an extra plane of atoms into a crystal lattice produces what?
Here are the choices:
A. spot location
B. spot dislocation
C. edge location
D. edge dislocation | Dislocations, Deformations, and Work Hardening Inserting an extra plane of atoms into a crystal lattice produces an edge dislocation. A familiar example of an edge dislocation occurs when an ear of corn contains an extra row of kernels between the other rows (). An edge dislocation in a crystal causes the planes of atoms in the lattice to deform where the extra plane of atoms begins (). The edge dislocation frequently determines whether the entire solid will deform and fail under stress. Deformation occurs when a dislocation moves through a crystal. To illustrate the process, suppose you have a heavy rug that is lying a few inches off-center on a nonskid pad. To move the rug to its proper place, you could pick up one end and pull it. Because of the large area of contact between the rug and the pad, however, they will probably move as a unit. Alternatively, you could pick up the rug and try to set it back down exactly where you want it, but that requires a great deal of effort (and probably at least one extra person). An easier solution is to create a small wrinkle at one end of the rug (an edge dislocation) and gradually push the wrinkle across, resulting in a net movement of the rug as a whole (part (a) in ). Moving the wrinkle requires only a small amount of energy because only a small part of the rug is actually moving at any one time. Similarly, in a solid, the contacts between layers are broken in only one place at a time, which facilitates the deformation process. Saylor URL: http://www. saylor. org/books. | D: edge dislocation. |
The core of a nuclear reactor generates a large amount of what type of energy from the decay of fission products, even when the power-producing fission chain reaction is turned off?
Here are the choices:
A. thermal
B. erosion
C. elastic
D. evaporation | Explain why the fission of heavy nuclei releases energy. Similarly, why is it that energy input is required to fission light nuclei? 19. Explain, in terms of conservation of momentum and energy, why collisions of neutrons with protons will thermalize neutrons better than collisions with oxygen. The ruins of the Chernobyl reactor are enclosed in a huge concrete structure built around it after the accident. Some rain penetrates the building in winter, and radioactivity from the building increases. What does this imply is happening inside? 21. Since the uranium or plutonium nucleus fissions into several fission fragments whose mass distribution covers a wide range of pieces, would you expect more residual radioactivity from fission than fusion? Explain. The core of a nuclear reactor generates a large amount of thermal energy from the decay of fission products, even when the power-producing fission chain reaction is turned off. Would this residual heat be greatest after the reactor has run for a long time or short time? What if the reactor has been shut down for months? 23. How can a nuclear reactor contain many critical masses and not go supercritical? What methods are used to control the fission in the reactor? 24. Why can heavy nuclei with odd numbers of neutrons be induced to fission with thermal neutrons, whereas those with even numbers of neutrons require more energy input to induce fission? 25. Why is a conventional fission nuclear reactor not able to explode as a bomb?. | A: thermal. |
Electric current is measured in coulombs per second, also called what?
Here are the choices:
A. joules
B. amperes
C. voltages
D. watts | Electric current is measured in coulombs per second, or amperes. | B: amperes. |
What is the name of the "point" that refers to the temperature at which water vapor condenses?
Here are the choices:
A. water point
B. melting point
C. dew point
D. brine point | You’ve probably noticed dew on the grass on a summer morning. Why does dew form? Remember that the land heats up and cools down fairly readily. So when night comes, the land cools. Air that was warm and humid in the daytime also cools over night. As the air cools, it can hold less water vapor. Some of the water vapor condenses on the cool surfaces, such as blades of grass. The temperature at which water vapor condenses is called the dew point . If this temperature is below freezing, ice crystals of frost form instead of dew ( Figure below ). The dew point occurs at 100 percent relative humidity. Can you explain why?. | C: dew point. |
Body plans do provide a succinct way to compare and contrast what?
Here are the choices:
A. missing animal features
B. key animal features
C. distinctive animal features
D. degenerative animal features | B: key animal features. | |
Once classified as plants, fungi have chitin rather than cellulose in what cell structures?
Here are the choices:
A. platelets
B. cell walls
C. mitochondria
D. cell ridges | Fungi used to be classified as plants. Now, they are known to have unique traits that set them apart from plants. For example, their cell walls contain chitin, not cellulose, and fungi absorb food rather than make their own. Below the level of the kingdom, fungi classification is controversial. | B: cell walls. |
What type of oceans are hostile to algae and cytoplankton?
Here are the choices:
A. warmer
B. shallower
C. colder
D. deeper | Warmer oceans are hostile to algae and cytoplankton , which are the most important absorbers of carbon dioxide. The loss of these two photosynthesizers would remove the most important natural sink. | A: warmer. |
Organelles whose membranes are specialized for aerobic respiration are called what?
Here are the choices:
A. chloroplasts
B. mitosis
C. vacuoles
D. mitochondria | Mitochondria are organelles whose membranes are specialized for aerobic respiration. | D: mitochondria. |
The regions of a material where the north and south poles of atoms are aligned are called what?
Here are the choices:
A. magnetic rays
B. cores
C. observed domains
D. magnetic domains | In other materials, there are regions where the north and south poles of atoms are all lined up in the same direction. These regions are called magnetic domains . Generally, the magnetic domains point in different directions, so the material is still not magnetic. However, the material can be magnetized (made into a magnet) by placing it in a magnetic field. When this happens, all the magnetic domains line up, and the material becomes a magnet. You can see this in the Figure below . Materials that can be magnitized are called ferromagnetic materials . They include iron, cobalt, and nickel. | D: magnetic domains. |
What is another term for body chromosomes?
Here are the choices:
A. quasars
B. subsets
C. Chromosomes
D. autosomes | In a given species, chromosomes can be identified by their number, size, centromere position, and banding pattern. In a human karyotype, autosomes or “body chromosomes” (all of the non–sex chromosomes) are generally organized in approximate order of size from largest (chromosome 1) to smallest (chromosome 22). The X and Y chromosomes are not autosomes. However, chromosome 21 is actually shorter than chromosome 22. This was discovered after the naming of Down syndrome as trisomy 21, reflecting how this disease results from possessing one extra chromosome 21 (three total). Not wanting to change the name of this important disease, chromosome 21 retained its numbering, despite describing the shortest set of chromosomes. The chromosome “arms” projecting from either end of the centromere may be designated as short or long, depending on their relative lengths. The short arm is abbreviated p (for “petite”), whereas the long arm is abbreviated q (because it follows “p” alphabetically). Each arm is further subdivided and denoted by a number. Using this naming system, locations on chromosomes can be described consistently in the scientific literature. | D: autosomes. |
Unlike amphibians, reptiles do not have what stage?
Here are the choices:
A. larval
B. reproductive
C. adult
D. egg | Unlike amphibians, reptiles do not have a larval stage. Instead, newly hatched reptiles look like smaller versions of the adults. They are able to move about on their own, but they are vulnerable to predators. Even so, most reptile parents provide no care to their hatchlings. In fact, most reptiles don’t even take care of their eggs. For example, female sea turtles lay their eggs on a sandy beach and then return to the ocean. The only exceptions are female crocodiles and alligators. They may defend their nest from predators and help the hatchlings reach the water. If the young remain in the area, the mother may continue to protect them for up to a year. | A: larval. |
What basic plant structure can add support and anchorage?
Here are the choices:
A. stems
B. roots
C. lower leaves
D. soils | B: roots. | |
Locus refers to the position of what on a chromosome, which controls the characteristics of an organism?
Here are the choices:
A. genome
B. gamete
C. rna
D. gene | Today, we known that characteristics of organisms are controlled by genes on chromosomes (see Figure below ). The position of a gene on a chromosome is called its locus . In sexually reproducing organisms, each individual has two copies of the same gene, as there are two versions of the same chromosome ( homologous chromosomes ). One copy comes from each parent. The gene for a characteristic may have different versions, but the different versions are always at the same locus. The different versions are called alleles . For example, in pea plants, there is a purple-flower allele ( B ) and a white-flower allele ( b ). Different alleles account for much of the variation in the characteristics of organisms. | D: gene. |
Fish hatch into larvae that are different from the adult form of?
Here are the choices:
A. color
B. parasites
C. sex
D. species | Fish hatch into larvae that are different from the adult form of the species. | D: species. |
What kind of islands provide natural protection to shorelines?
Here are the choices:
A. patch islands
B. locational islands
C. edge islands
D. barrier islands | Barrier islands provide natural protection to shorelines. Storm waves strike the barrier island before they reach the shore. People also build artificial barriers, called breakwaters . Breakwaters also protect the shoreline from incoming waves. You can see an example of a breakwater in Figure below . It runs parallel to the coast like a barrier island. | D: barrier islands. |
Fruit-eating bats receive food from plants and, in return, help these plants by doing what?
Here are the choices:
A. protecting them
B. pollinating seeds
C. fertilizing them
D. spreading seeds | Fruit-eating bats ( Figure below ) also receive food from plants. In return, they help these plants spread their seeds. When bats consume fruit, they also consume the seeds within the fruit. Then they carry the seeds in their guts to far-away locations. | D: spreading seeds. |
What is determined by the amount of energy in molecules?
Here are the choices:
A. momentum
B. state of matter
C. radioactivity
D. kingdom | The amount of energy in molecules of matter determines the state of matter . Matter can exist in one of several different states, including a gas, liquid, or solid state. These different states of matter have different properties, which are illustrated in Figure below . Gasses have the most energy, and solids have the least energy. | B: state of matter. |
Biomass is the mass of biological what?
Here are the choices:
A. lipids
B. proteins
C. organisms
D. tissues | Biomass is the mass of biological organisms. It is usually used to describe the amount of organic matter in a trophic level of an ecosystem. Biomass production involves using organic matter ("biomass") from plants to create electricity. Using corn to make ethanol fuel is an example of biomass generated energy. Biomass is generally renewable. | C: organisms. |
The primary nitrogenous waste material secreted by ureotelic animals is what substance?
Here are the choices:
A. urea
B. nitrate
C. carbon
D. ammonia | invertebrates produce uric acid. Animals that secrete urea as the primary nitrogenous waste material are called ureotelic animals. | A: urea. |
What system makes sure leaked blood returns back to the bloodstream?
Here are the choices:
A. somatic
B. cerebral
C. symptomatic
D. lymphatic | You may think that your blood vessels have thick walls without any leaks, but that's not true. Blood vessels can leak just like any other pipe. The lymphatic system makes sure leaked blood returns back to the bloodstream. | D: lymphatic. |
Enthalpy changes are measured by using what?
Here are the choices:
A. fluorescence
B. calorimetry
C. inversion
D. infraction | Enthalpy changes are measured by using calorimetry. | B: calorimetry. |
The cell walls of fungi are made of what?
Here are the choices:
A. cartilage
B. chitin
C. mucous
D. lectin | Today, fungi are no longer classified as plants. We now know that they have unique physical, chemical, and genetic traits that set them apart from plants (and other eukaryotes). For example, the cell walls of fungi are made of chitin, not cellulose. Also, fungi absorb nutrients from other organisms, whereas plants make their own food. These are just a few of the reasons fungi are now placed in their own kingdom. | B: chitin. |
When blood engorged capillaries leak fluid into neighboring tissues, what occurs?
Here are the choices:
A. infection
B. swelling
C. bleeding
D. seeping | B: swelling. | |
Will contour lines ever cross?
Here are the choices:
A. yes
B. in rare cases
C. no
D. always | In some soils, the organic portion is entirely missing. This is true of desert sand. At the other extreme, a soil may be completely organic. Peat, found in a bog or swamp, is totally organic soil. Organic materials are necessary for a soil to be fertile. The organic portion provides the nutrients needed for strong plant growth. | C: no. |
Species of organisms that have permanently died out can also be called what?
Here are the choices:
A. inherited
B. occuring
C. succinct
D. extinct | Most of the organisms that once lived on Earth are now extinct. Earth’s environment has changed many times. Many organisms could not adapt to the changes. They died out. The organisms that did survive passed traits on to their offspring. The changes added up, eventually producing the species we see today. | D: extinct. |
Are the majority of archaea chemotrophs or photosynthetic?
Here are the choices:
A. neither
B. chemotrophs
C. photosynthetics
D. autotrophs | Most archaea are chemotrophs and derive their energy and nutrients from breaking down molecules in their environment. A few species of archaea are photosynthetic and capture the energy of sunlight. Unlike bacteria, which can be parasites and are known to cause a variety of diseases, there are no known archaea that act as parasites. Some archaea do live within other organisms. But these archea form mutualistic relationships with their host, where both the archaea and the host benefit. In other words, they assist the host in some way, for example by helping to digest food. | B: chemotrophs. |
Oxygen is essentially just a waste product of the light reactions of what?
Here are the choices:
A. photosynthesis
B. Fibrinolysis
C. electrolysis
D. glycolysis | You could argue that oxygen is one of the most important, if not THE most important molecule necessary for life. However, oxygen is essentially just a waste product of the light reactions of photosynthesis. It is a "leftover" from a necessary part of the process. All the oxygen that is necessary to maintain most forms of life just happens to be released from the plant during this process. | A: photosynthesis. |
What is the process by which almost all plants make food?
Here are the choices:
A. reactions
B. melting
C. photosynthesis
D. digestion | Almost all plants make food by photosynthesis. Only about 1 percent of the estimated 300,000 species of plants have lost the ability to photosynthesize. These other species are consumers, many of them predators. How do plants prey on other organisms? The Venus fly trap in Figure below shows one way this occurs. | C: photosynthesis. |
Some enzymes require the presence of a non-protein molecule to function properly. what is that molecule called?
Here are the choices:
A. cofactor
B. coenzymes
C. substrate
D. prothetic | Some enzymes require the presence of a non-protein molecule called a cofactor in order to function properly. Cofactors can be inorganic metal ions or small organic molecules. Many vitamins, such as B vitamins, act as cofactors. Some metal ions which function as cofactors for various enzymes include zinc, magnesium, potassium, and iron. | A: cofactor. |
What stimulates the changes of pubery?
Here are the choices:
A. sex hormones
B. sex education
C. parenting
D. mutation | The gonads are glands that secrete sex hormones. Male gonads are called testes. They secrete the male sex hormone testosterone. The female gonads are called ovaries. They secrete the female sex hormone estrogen. Sex hormones stimulate the changes of puberty. They also control the production of sperm or eggs by the gonads. | A: sex hormones. |
What are the male reproductive cells called?
Here are the choices:
A. sperm
B. ova
C. mucus
D. plasma | Sperm ( Figure below ), the male reproductive cells, are tiny. In fact, they are the smallest cells in the human body. What do you think a sperm cell looks like? Some people think that it looks like a tadpole. Do you agree?. | A: sperm. |
What is one function of the nervous system in humans?
Here are the choices:
A. controlling muscles
B. producing hormones
C. controlling emotion
D. controlling thought | Controlling muscles and maintaining balance are just two of the functions of the human nervous system. What else does the nervous system do?. | A: controlling muscles. |
What is the diversity of living things called?
Here are the choices:
A. degradation
B. ecosystem
C. life cycle
D. biodiversity | Life on Earth is very diverse. The diversity of living things is called biodiversity . A measure of Earth’s biodiversity is the number of different species of organisms that live on Earth. At least 10 million different species live on Earth today. They are commonly grouped into six different kingdoms. Examples of organisms within each kingdom are shown in Figure below . | D: biodiversity. |
What kind of mammalian reproduction is risky for the offspring but not the mother?
Here are the choices:
A. monotreme
B. cactaceae
C. sexual
D. asexual | Monotreme reproduction is the least risky for the mother. However, eggs are harder to protect than is an embryo or a fetus in a pouch or uterus. Therefore, monotreme offspring may have a lower chance of surviving than the offspring of therian mammals. | A: monotreme. |
What do we call the force of attraction or repulsion between electrically charged particles?
Here are the choices:
A. chemical force
B. mechanical force
C. gravitational pull
D. electromagnetic force | Electromagnetic force is a force of attraction or repulsion between all electrically charged particles. This force is transferred between charged particles of matter by fundamental force-carrying particles called photons. Because of electromagnetic force, particles with opposite charges attract each other and particles with the same charge repel each other. | D: electromagnetic force. |
Mendeleev organized what basic units into rows and columns?
Here are the choices:
A. animals
B. elements
C. compounds
D. solutions | You can see how Mendeleev organized the elements in the Figure below . From left to right across each row, elements are arranged by increasing atomic mass. Mendeleev discovered that if he placed eight elements in each row and then continued on to the next row, the columns of the table would contain elements with similar properties. He called the columns groups . They are sometimes called families, because elements within a group are similar but not identical to one another, like people in a family. | B: elements. |
What do you call compounds that have covalent bonds?
Here are the choices:
A. valence compound
B. covalent compounds
C. ions
D. reflectivity compounds | Covalent bonds are bonds in which atoms share rather than transfer electrons. Compounds with covalent bonds are called covalent compounds. | B: covalent compounds. |
What is the term for magma that erupts onto earth's surface?
Here are the choices:
A. obsidian
B. steam
C. debris
D. lava | Some places inside Earth are so hot that rock melts. Melted rock inside the Earth is called magma. Magma can be hotter than 1,000 o C. When magma erupts onto Earth’s surface, it is known as lava ( Figure below ). Minerals form when magma and lava cool. Some minerals crystallize at hotter temperatures. These minerals form first. Other minerals form at cooler temperatures. These minerals form later. | D: lava. |
What changes nitrogen gas from the atmosphere to nitrogen compounds that plants can absorb?
Here are the choices:
A. pathogens
B. viruses
C. bacteria
D. tumors | Bacteria change nitrogen gas from the atmosphere to nitrogen compounds that plants can absorb. | C: bacteria. |
In vertebrates, ovipary, ovovivipary, and vivipary are different strategies for what vital process?
Here are the choices:
A. circulation
B. respiration
C. absorption
D. reproduction | Vertebrates have one of three reproductive strategies, known as ovipary, ovovivipary, or vivipary. | D: reproduction. |
What waves do radio and television use?
Here are the choices:
A. light waves
B. radio waves
C. gamma waves
D. sound waves | Radio waves are electromagnetic waves with the longest wavelengths, lowest frequencies, and least amount of energy. They are used for radio and television broadcasts and many other purposes. | B: radio waves. |
Which factor causes a cannon ball to move horizontally and then fall on the ground?
Here are the choices:
A. downward motion
B. fluid motion
C. cone motion
D. projectile motion | Earth’s gravity also affects the acceleration of objects that start out moving horizontally, or parallel to the ground. Look at Figure below . A cannon shoots a cannon ball straight ahead, giving the ball horizontal motion. At the same time, gravity pulls the ball down toward the ground. Both forces acting together cause the ball to move in a curved path. This is called projectile motion . | D: projectile motion. |
What do electrons lose during their transfer from organic compounds to oxygen?
Here are the choices:
A. mechanical energy
B. actual energy
C. thermal energy
D. potential energy | D: potential energy. | |
What are plastids that contain other pigments?
Here are the choices:
A. chromoplasts
B. cytoplasm
C. chloroplasts
D. lucoplasts | Chromoplasts are plastids that contain other pigments. These other pigments give flowers and fruits their colors. | A: chromoplasts. |
Each species of legume is associated with a strain of __________
Here are the choices:
A. rhizobium
B. fungi
C. heliotropium
D. agrobacterium | A: rhizobium. | |
Algae convert energy from the sun into food by means of what process?
Here are the choices:
A. luminosynthesis
B. compression
C. glycolysis
D. photosynthesis | Algae is sometimes mocked as a source of fuel. But algae are a potentially wonderful source of power. They convert energy from the Sun into food by photosynthesis. Algae can be grown in desert areas where other crops cannot grow. Nutrients for algae may be wastes from other processes. Algae can be processed to be made into a liquid. There is a lot of research going on to harness algae for biofuels. | D: photosynthesis. |
Which process helps provide cleaner water for agriculture?
Here are the choices:
A. sterilization
B. osmosis
C. process of desalinization
D. purification | Fresh water is essential for good crops. In some areas of the world, there is enough rain to accomplish this task. In other locales, water must be provided so the crops will grow. Worldwide, irrigation covers about 18% of farm land and produces some 40% of crops. A major source of cleaner water in many parts of the world is provided by the process of desalinization . | C: process of desalinization. |
What element is an essential part of many molecules needed by living organisms?
Here are the choices:
A. helium
B. nitrogen
C. silicon
D. hydrogen | Nitrogen is an essential part of many molecules needed by living organisms. | B: nitrogen. |
An atom is the smallest unit of what that maintains the identity of the latter?
Here are the choices:
A. element
B. cell
C. organism
D. mixture | The smallest piece of an element that maintains the identity of that element is called an atom. Individual atoms are extremely small. It would take about fifty million atoms in a row to make a line that is 1 cm long. The period at the end of a printed sentence has several million atoms in it. Atoms are so small that it is difficult to believe that all matter is made from atoms—but it is. The concept that atoms play a fundamental role in chemistry is formalized by the modern atomic theory, first stated by John Dalton, an English scientist, in 1808. It consists of three parts: 1. | A: element. |
When a solution freezes, only what particles come together to form a solid phase, while the presence of solute particles interferes with that process?
Here are the choices:
A. diluent
B. hydrogen
C. pigment
D. solvent | The presence of solute particles has the opposite effect on the freezing point of a solution. When a solution freezes, only the solvent particles come together to form a solid phase, and the presence of solute particles interferes with that process. Therefore, for the liquid solvent to freeze, more energy must be removed from the solution, which lowers the temperature. Thus, solutions have lower freezing points than pure solvents do. This phenomenon is called freezing point depression. For every mole of particles in a liter of water, the freezing point decreases by about 1.9°C. Both boiling point elevation and freezing point depression have practical uses. For example, solutions of water and ethylene glycol (C2H6O2) are used as coolants in automobile engines because the boiling point of such a solution is greater than 100°C, the normal boiling point of water. In winter, salts like NaCl and CaCl2 are sprinkled on the ground to melt ice or keep ice from forming on roads and sidewalks. This is because the solution made by dissolving sodium chloride or calcium chloride in water has a lower freezing point than pure water, so the formation of ice is inhibited. | D: solvent. |
Liquefaction ccurs when the molecules of a gas are cooled to the point where they no longer possess sufficient kinetic energy to overcome what?
Here are the choices:
A. bonding attractive forces
B. gravitational attractive forces
C. intermolecular attractive forces
D. intermolecular gravitational forces | Liquefaction of Gases Liquefaction of gases is the condensation of gases into a liquid form, which is neither anticipated nor explained by the kinetic molecular theory of gases. Both the theory and the ideal gas law predict that gases compressed to very high pressures and cooled to very low temperatures should still behave like gases, albeit cold, dense ones. As gases are compressed and cooled, however, they invariably condense to form liquids, although very low temperatures are needed to liquefy light elements such as helium (for He, 4.2 K at 1 atm pressure). Liquefaction can be viewed as an extreme deviation from ideal gas behavior. It occurs when the molecules of a gas are cooled to the point where they no longer possess sufficient kinetic energy to overcome intermolecular attractive forces. The precise combination of temperature and pressure needed to liquefy a gas depends strongly on its molar mass and structure, with heavier and more complex molecules usually liquefying at higher temperatures. In general, substances with large van der Waals acoefficients are relatively easy to liquefy because large a coefficients indicate relatively strong intermolecular attractive interactions. Conversely, small molecules with only light elements have small a coefficients, indicating weak intermolecular interactions, and they are relatively difficult to liquefy. Gas liquefaction is used on a massive scale to separate O2, N2, Ar, Ne, Kr, and Xe. After a sample of air is liquefied, the mixture is. | C: intermolecular attractive forces. |
What is the term for the series of life stages and events that a sexually reproducing organism goes through?
Here are the choices:
A. existence
B. age
C. society cycle
D. life cycle | Sexual reproduction occurs in a cycle. Diploid parents produce haploid gametes that unite and develop into diploid adults, which repeat the cycle. This series of life stages and events that a sexually reproducing organism goes through is called its life cycle . Sexually reproducing organisms can have different types of life cycles. Three are represented in Figure below and described following sections. | D: life cycle. |
What is absorbed from food waste in the large intestine before it passes out of the body as feces?
Here are the choices:
A. inactive water
B. distilled water
C. dependent water
D. excess water | Excess water is absorbed from food waste in the large intestine before it passes out of the body through the anus as feces. Trillions of helpful bacteria also live in the large intestine. They carry out important roles, such as making vitamins. | D: excess water. |
What do hydrocarbons consist of?
Here are the choices:
A. carbon and oxygen
B. carbon and helium
C. carbon and water
D. carbon and hydrogen | D: carbon and hydrogen. | |
A major diversification of what animal group occurred about 50 million years ago, possibly spurred by worldwide climate change?
Here are the choices:
A. mammals
B. reptiles
C. amphibians
D. insects | The supertree also shows that another major diversification of mammals occurred about 50 million years ago. Again, worldwide climate change may have been one reason. This time Earth’s temperature rose. The warmer temperature led to a greater diversity of plants. This would have meant more food for mammals or their prey. | A: mammals. |
Like a house, your body has what kind of mechanism that responds to changes in temperature?
Here are the choices:
A. internal thermostat
B. mechanical thermostat
C. external thermostat
D. sensitive thermostat | For example, your body has an internal thermostat. During a winter day, in your house a thermostat senses the temperature in a room and responds by turning on or off the heater. Your body acts in much the same way. When body temperature rises, receptors in the skin and the brain sense the temperature change. The temperature change triggers a command from the brain. This command can cause several responses. If you are too hot, the skin makes sweat and blood vessels near the skin surface dilate. This response helps decrease body temperature. | A: internal thermostat. |
An isometric type of what occurs as the muscle produces tension without changing the angle of a skeletal joint?
Here are the choices:
A. compression
B. acceleration
C. contraction
D. extension | 10.4 | Nervous System Control of Muscle Tension By the end of this section, you will be able to: • Explain concentric, isotonic, and eccentric contractions • Describe the length-tension relationship • Describe the three phases of a muscle twitch • Define wave summation, tetanus, and treppe To move an object, referred to as load, the sarcomeres in the muscle fibers of the skeletal muscle must shorten. The force generated by the contraction of the muscle (or shortening of the sarcomeres) is called muscle tension. However, muscle tension also is generated when the muscle is contracting against a load that does not move, resulting in two main types of skeletal muscle contractions: isotonic contractions and isometric contractions. In isotonic contractions, where the tension in the muscle stays constant, a load is moved as the length of the muscle changes (shortens). There are two types of isotonic contractions: concentric and eccentric. A concentric contraction involves the muscle shortening to move a load. An example of this is the biceps brachii muscle contracting when a hand weight is brought upward with increasing muscle tension. As the biceps brachii contract, the angle of the elbow joint decreases as the forearm is brought toward the body. Here, the biceps brachii contracts as sarcomeres in its muscle fibers are shortening and cross-bridges form; the myosin heads pull the actin. An eccentric contraction occurs as the muscle tension diminishes and the muscle lengthens. In this case, the hand weight is lowered in a slow and controlled manner as the amount of crossbridges being activated by nervous system stimulation decreases. In this case, as tension is released from the biceps brachii, the angle of the elbow joint increases. Eccentric contractions are also used for movement and balance of the body. An isometric contraction occurs as the muscle produces tension without changing the angle of a skeletal joint. Isometric contractions involve sarcomere shortening and increasing muscle tension, but do not move a load, as the force produced cannot overcome the resistance provided by the load. For example, if one attempts to lift a hand weight that is too heavy, there will be sarcomere activation and shortening to a point, and ever-increasing muscle tension, but no change in the angle of the elbow joint. In everyday living, isometric contractions are active in maintaining posture and maintaining bone and joint stability. However, holding your head in an upright position occurs not because the muscles cannot move the head, but. | C: contraction. |
What are important coenzymes or precursors of coenzymes, and are required for enzymes to function properly?
Here are the choices:
A. Drugs
B. carbohydrates
C. vitamins
D. supplements | Figure 6.20 Vitamins are important coenzymes or precursors of coenzymes, and are required for enzymes to function properly. Multivitamin capsules usually contain mixtures of all the vitamins at different percentages. | C: vitamins. |
What have cell-surface antigen receptors for foreign molecules?
Here are the choices:
A. dendrites
B. lymphocytes
C. capillaries
D. erythrocytes | B: lymphocytes. | |
In birds, modified front legs are actually what?
Here are the choices:
A. wings
B. tails
C. arms
D. claws | Wings are an obvious adaptation for flight. They are actually modified front legs. Birds move their wings using muscles in the chest. These muscles are quite large, making up as much as 35 percent of a bird’s body weight. | A: wings. |
The number of waves that pass a fixed point in a given amount of time is called what?
Here are the choices:
A. frequency of a wave
B. spread of a wave
C. wavelength of a wave
D. spectroscopy of a wave | A photon isn’t a fixed amount of energy. Instead, the amount of energy in a photon depends on the frequency of the electromagnetic wave. The frequency of a wave is the number of waves that pass a fixed point in a given amount of time, such as the number of waves per second. In waves with higher frequencies, photons have more energy. | A: frequency of a wave. |
How does litmus paper indicate the ph value of a solution?
Here are the choices:
A. by texture
B. by shape
C. by color
D. by smell | There are two common ways to measure pH. When only an approximate pH value is needed, an inexpensive test involves the use of acid-base indicators , which change color based on the relative acidity of the solution. One type of common indicator is litmus paper. For example, if a piece of litmus paper is dipped into an acidic solution (pH below ~4.5), it will turn red, and dipping it into a basic solution (pH above ~8.5) will turn it blue. Solutions of intermediate pH will result in various shades of purple. Because different indicators change color at different pH values, the use of multiple indicators can generally narrow down the possible pH of a solution to a range of about 0.5-1 pH units. Figure below shows the colors exhibited by various indicators at different pH values. | C: by color. |
What is another term for movable joints?
Here are the choices:
A. synovial
B. sesamoidal
C. fibrous
D. interstitial | Movable joints are also known as synovial joints . This is because the space between the bones is filled with a thick fluid, called synovial fluid , that cushions the joint (see Figure below ). | A: synovial. |
What device is a magnetic disc that provides long-term storage for programs and data?
Here are the choices:
A. software
B. hard drive
C. cassette
D. floppy drive | The hard drive is a magnetic disc that provides long-term storage for programs and data. | B: hard drive. |
Debroglie proposed in 1924 that any object exhibits a wavelength that is inversely proportional to its?
Here are the choices:
A. inertia
B. momentum
C. frequency
D. velocity | DeBroglie proposed in 1924 that any object exhibits a wavelength that is inversely proportional to its momentum. Because of this relationship, only very tiny particles will exhibit measurable wavelengths. | B: momentum. |
What travels at the interface between the sea surface and the atmosphere?
Here are the choices:
A. ocean tides
B. ocean breeze
C. ocean waves
D. ocean currents | Yes, in some ways. Ocean waves travel at the interface between the sea surface and the atmosphere. They have all the features that all waves have. Some seismic waves also travel at an interface. Which ones?. | C: ocean waves. |
What is the only light that humans can see?
Here are the choices:
A. bright light
B. dark light
C. visible light
D. distinct light | Visible light is the only light that humans can see. Different wavelengths of visible light appear as different colors. Radio waves have the longest wavelengths. They also have the least amount of energy. Infrared light has wavelengths too long for humans to see, but we can feel them as heat. The atmosphere absorbs the infrared light. Ultraviolet (UV) light is in wavelengths too short for humans to see. The most energetic UV light is harmful to life. The atmosphere absorbs most of this UV light from the Sun. Gamma rays have the highest energy and they are the most damaging rays. Fortunately, gamma rays don’t penetrate Earth’s atmosphere. | C: visible light. |
What directs the amino acids to be introduced into the growing protein chain in the proper sequence?
Here are the choices:
A. gene template
B. organism template
C. organelle template
D. rna template | The process of protein synthesis is summarized in the Figure below . DNA produces an RNA template that directs the amino acids to be introduced into the growing protein chain in the proper sequence. A specific transfer RNA attaches to each amino acid and brings it to the RNA for incorporation. | D: rna template. |
Cellular respiration in humans involves the combustion of what simple sugar?
Here are the choices:
A. glutamate
B. insulin
C. glucose
D. starch | Your own body cells burn fuel in combustion reactions. The fuel is glucose (C 6 H 12 O 6 ), a simple sugar. The process in which combustion of glucose occurs in body cells is called cellular respiration. This combustion reaction provides energy for life processes. Cellular respiration can be summed up by the equation:. | C: glucose. |
What still causes fatal lung disease in nonsmokers?
Here are the choices:
A. tobacco smoke
B. nicotine
C. chewing tobacco
D. alcohol | tobacco smoke causes fatal lung disease in nonsmokers. | A: tobacco smoke. |
Like ants and termites, they grow fungi inside the bark of trees and use it to help do what?
Here are the choices:
A. weaken enemies
B. clean the nest
C. kill prey
D. digest food | Ambrosia beetles live in the bark of trees. Like ants and termites, they grow fungi inside the bark of trees and use it to help digest their food. | D: digest food. |
For fertilization to occur in angiosperms, pollen has to be transferred to the stigma of what?
Here are the choices:
A. root
B. stem
C. flower
D. leaf | 32.2 Pollination and Fertilization For fertilization to occur in angiosperms, pollen has to be transferred to the stigma of a flower: a process known as pollination. Gymnosperm pollination involves the transfer of pollen from a male cone to a female cone. When the pollen of the flower is transferred to the stigma of the same flower, it is called self-pollination. Cross-pollination occurs when pollen is transferred from one flower to another flower on the same plant, or another plant. Cross-pollination requires pollinating agents such as water, wind, or animals, and increases genetic diversity. After the pollen lands on the stigma, the tube cell gives rise to the pollen tube, through which the generative nucleus migrates. The pollen tube gains entry through the micropyle on the ovule sac. The generative cell divides to form two sperm cells: one fuses with the egg to form the diploid zygote, and the other fuses with the polar nuclei to form the endosperm, which is triploid in nature. This is known as double fertilization. After fertilization, the zygote divides to form the embryo and the fertilized ovule forms the seed. The walls of the ovary form the fruit in which the seeds develop. The seed, when mature, will germinate under favorable conditions and give rise to the diploid sporophyte. | C: flower. |
Exothermic reactions in organisms are called what?
Here are the choices:
A. biogenic reactions
B. catabolic reactions
C. nebular reactions
D. nuclear reactions | Exothermic reactions in organisms are called catabolic reactions . These reactions break down molecules into smaller units and release energy. An example of a catabolic reaction is the breakdown of glucose, which releases energy that cells need to carry out life processes. Endothermic reactions in organisms are called anabolic reactions . These reactions build up bigger molecules from smaller ones. An example of an anabolic reaction is the joining of amino acids to form a protein. Which type of reactions—catabolic or anabolic—do you think occur when your body digests food?. | B: catabolic reactions. |
Prior to birth, the lungs are filled with amniotic fluid, mucus, and what else?
Here are the choices:
A. surfactant
B. air
C. plasma
D. blood | Birth Prior to birth, the lungs are filled with amniotic fluid, mucus, and surfactant. As the fetus is squeezed through the birth canal, the fetal thoracic cavity is compressed, expelling much of this fluid. Some fluid remains, however, but is rapidly absorbed by the body shortly after birth. The first inhalation occurs within 10 seconds after birth and not only serves as the first inspiration, but also acts to inflate the lungs. Pulmonary surfactant is critical for inflation to occur, as it reduces the surface tension of the alveoli. Preterm birth around 26 weeks frequently results in severe respiratory distress, although with current medical advancements, some babies may survive. Prior to 26 weeks, sufficient pulmonary surfactant is not produced, and the surfaces for gas exchange have not formed adequately; therefore, survival is low. | A: surfactant. |
At what point during a chemical reaction is there no net change?
Here are the choices:
A. ionization
B. equilibrium
C. bonding
D. formation | Most chemical reactions reach equilibrium at which point there is no net change. | B: equilibrium. |
The solution with the higher solute concentration is called what?
Here are the choices:
A. hypotonic
B. hypertonic
C. unsaturated
D. acetic | In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is hypertonic, and the solution with the lower concentration is hypotonic. Solutions of equal solute concentration are isotonic. | B: hypertonic. |
The three stages of transcription are initiation, elongation, and what?
Here are the choices:
A. prolongation
B. degradation
C. separation
D. termination | D: termination. | |
A rounded hollow carved in the side of a mountain by a glacier is known as?
Here are the choices:
A. a cavern
B. a crater
C. a crest
D. a cirque | A cirque is a rounded hollow carved in the side of a mountain by a glacier. The highest cliff of a cirque is called the headwall. | D: a cirque. |
Where do most cnidarians live?
Here are the choices:
A. grass
B. rocks
C. ocean
D. hills | Cnidarians are invertebrates such as jellyfish and corals. They belong to the phylum Cnidaria. All cnidarians are aquatic. Most of them live in the ocean. Cnidarians are a little more complex than sponges. They have radial symmetry and tissues. There are more than 10,000 cnidarian species. They are very diverse, as shown in Figure below . | C: ocean. |
What do a group of cells that work together form?
Here are the choices:
A. tissue
B. organ
C. organelle
D. molecule | Cells are grouped together to carry out specific functions. A group of cells that work together form a tissue . Your body has four main types of tissues, as do the bodies of other animals. These tissues make up all structures and contents of your body. An example of each tissue type is pictured in the Figure below . | A: tissue. |
Plants alternate between haploid and what?
Here are the choices:
A. diploid
B. monoplooid
C. monoxoid
D. triploid | Plants alternate between haploid and diploid generations. Haploid cells have one of each pair of chromosomes. Diploid cells have two of each pair. | A: diploid. |
Temperature is a measure of the motion (kinetic energy) of what?
Here are the choices:
A. molecules
B. particles
C. electrons
D. nucleus | Water Stabilizes Temperature The hydrogen bonds in water allow it to absorb and release heat energy more slowly than many other substances. Temperature is a measure of the motion (kinetic energy) of molecules. As the motion increases, energy is higher and thus temperature is higher. Water absorbs a great deal of energy before its temperature rises. Increased energy disrupts the hydrogen bonds between water molecules. Because these bonds can be created and disrupted rapidly, water absorbs an increase in energy and temperature changes only minimally. This means that water moderates temperature changes within organisms and in their environments. As energy input continues, the balance between hydrogen-bond formation and destruction swings toward the destruction side. More bonds are broken than are formed. This process results in the release of individual water molecules at the surface of the liquid (such as a body of water, the leaves of a plant, or the skin of an organism) in a process called evaporation. Evaporation of sweat, which is 90 percent water, allows for cooling of an organism, because breaking hydrogen bonds requires an input of energy and takes heat away from the body. Conversely, as molecular motion decreases and temperatures drop, less energy is present to break the hydrogen bonds between water molecules. These bonds remain intact and begin to form a rigid, lattice-like structure (e. , ice) (Figure 2.9a). When frozen, ice is less dense than liquid water (the molecules are farther apart). This means that ice floats on the surface of a body of water (Figure 2.9b). In lakes, ponds, and oceans, ice will form on the surface of the water, creating an insulating barrier to protect the animal and plant life beneath from freezing in the water. If this did not happen, plants and animals living in water would freeze in a block of ice and could not move freely, making life in cold temperatures difficult or impossible. | A: molecules. |
What method do scientists use to answer questions?
Here are the choices:
A. scientific method
B. regulatory method
C. solutive method
D. inquisitive method | Scientists use the scientific method to answer questions. The scientific method is a series of steps. These steps help scientists (or even just people!) investigate a question. | A: scientific method. |
What is the natural selection that favors altruistic behavior by enhancing reproductive success of relatives known as?
Here are the choices:
A. directional selection
B. stabilizing selection
C. diversifying selection
D. kin selection | D: kin selection. | |
When a male directly deposits sperm in a female during mating, this is considered what type of fertilization?
Here are the choices:
A. internal
B. mechanical
C. external
D. dual | Internal Fertilization Internal fertilization occurs most often in terrestrial animals, although some aquatic animals also use this method. Internal fertilization may occur by the male directly depositing sperm in the female during mating. It may also occur by the male depositing sperm in the environment, usually in a protective structure, which a female picks up to deposit the sperm in her reproductive tract. There are three ways that offspring are produced following internal fertilization. In oviparity, fertilized eggs are laid outside the female’s body and develop there, receiving nourishment from the yolk that is a part of the egg (Figure 18.7a). This occurs in some bony fish, some reptiles, a few cartilaginous fish, some amphibians, a few mammals, and all birds. Most non-avian reptiles and insects produce leathery eggs, while birds and some turtles produce eggs with high concentrations of calcium carbonate in the shell, making them hard. Chicken eggs are an example of a hard shell. The eggs of the egg-laying mammals such as the platypus and echidna are leathery. In ovoviparity, fertilized eggs are retained in the female, and the embryo obtains its nourishment from the egg’s yolk. The eggs are retained in the female’s body until they hatch inside of her, or she lays the eggs right before they hatch. This process helps protect the eggs until hatching. This occurs in some bony fish (like the platyfish Xiphophorus maculatus, Figure 18.7b), some sharks, lizards, some snakes (garter snake Thamnophis sirtalis), some vipers, and some invertebrate animals (Madagascar hissing cockroach Gromphadorhina portentosa). In viviparity the young are born alive. They obtain their nourishment from the female and are born in varying states of maturity. This occurs in most mammals (Figure 18.7c), some cartilaginous fish, and a few reptiles. | A: internal. |
What part of the body does the mycobacterium tuberculosis bacterium usually attack?
Here are the choices:
A. muscles
B. lungs
C. heart
D. Pancreas | This bacterium, called Mycobacterium tuberculosis , causes the disease Tuberculosis (TB). These bacteria usually attack the lungs. If left untreated, the infection can be fatal. Many other illnesses, mild and severe, are also caused by certain types of bacteria. | B: lungs. |
Conversely, very large forces are created by liquids and solids when they try to expand but are constrained from doing so—which is equivalent to compressing them to less than their normal volume. this often occurs when a contained material warms up, since most materials expand when they do this?
Here are the choices:
A. increase temperature
B. increase density
C. increase mass
D. decrease temperature | Conversely, very large forces are created by liquids and solids when they try to expand but are constrained from doing so—which is equivalent to compressing them to less than their normal volume. This often occurs when a contained material warms up, since most materials expand when their temperature increases. If the materials are tightly constrained, they deform or break their container. Another very common example occurs when water freezes. Water, unlike most materials, expands when it freezes, and it can easily fracture a boulder, rupture a biological cell, or crack an engine block that gets in its way. Other types of deformations, such as torsion or twisting, behave analogously to the tension, shear, and bulk deformations considered here. | A: increase temperature. |
What helps regulate the production of urine?
Here are the choices:
A. the pituitary gland
B. the discrete gland
C. the temporal gland
D. the fetal gland | Patrick J. Lynch, modified by CK-12 Foundation. The pituitary gland helps regulate the production of urine . CC BY 2.0. | A: the pituitary gland. |
In celsius, what is the temperature at which water freezes?
Here are the choices:
A. 100 degrees
B. absolute zero
C. zero degrees
D. 32 degrees | A: If calcium chloride dissolves in water, it breaks down into its ions (Ca 2+ and Cl - ). When water has ions dissolved in it, it has a lower freezing point. Pure water freezes at 0°C. With calcium and chloride ions dissolved in it, it won’t freeze unless the temperature reaches -29°C or lower. | C: zero degrees. |
Which theory explains how materials can collide and become new materials?
Here are the choices:
A. collision theory
B. pileup theory
C. rupture theory
D. disturbance theory | Collision theory explains how materials can collide and become new materials. | A: collision theory. |
What 3 types of friction occur between solid surfaces?
Here are the choices:
A. static, sliding, rolling
B. static,desending,sliding
C. static , ascending , rolling
D. static , arching , rolling | Friction is the force that opposes motion between any surfaces that are in contact. There are four types of friction: static, sliding, rolling, and fluid friction. Static, sliding, and rolling friction occur between solid surfaces. Fluid friction occurs in liquids and gases. All four types of friction are described below. You can see a video demonstration of the different types at this URL:. | A: static, sliding, rolling. |
Name the 3 ocean zones.
Here are the choices:
A. intertidal, pelagic, benthic
B. amphidromic, cotidal, benthic
C. coral, intertidal, apogean
D. cotidal, intertidal, exotidal | Zones in the oceans include the intertidal, pelagic, and benthic zones. The types of organisms found in these ocean zones are also determined by such factors as depth of water and distance from shore, among other factors. | A: intertidal, pelagic, benthic. |
Secondary consumers are usually carnivores that eat what?
Here are the choices:
A. dead material
B. primary consumers
C. soil
D. plants | Food Chains and Food Webs The term “food chain” is sometimes used metaphorically to describe human social situations. In this sense, food chains are thought of as a competition for survival, such as “who eats whom?” Someone eats and someone is eaten. Therefore, it is not surprising that in our competitive “dog-eat-dog” society, individuals who are considered successful are seen as being at the top of the food chain, consuming all others for their benefit, whereas the less successful are seen as being at the bottom. The scientific understanding of a food chain is more precise than in its everyday usage. In ecology, a food chain is a linear sequence of organisms through which nutrients and energy pass: primary producers, primary consumers, and higher-level consumers are used to describe ecosystem structure and dynamics. There is a single path through the chain. Each organism in a food chain occupies what is called a trophic level. Depending on their role as producers or consumers, species or groups of species can be assigned to various trophic levels. In many ecosystems, the bottom of the food chain consists of photosynthetic organisms (plants and/or phytoplankton), which are called primary producers. The organisms that consume the primary producers are herbivores: the primary consumers. Secondary consumers are usually carnivores that eat the primary consumers. Tertiary consumers are carnivores that eat other carnivores. Higher-level consumers feed on the next lower tropic levels, and so on, up to the organisms at the top of the food chain: the apex consumers. In the Lake Ontario food chain shown in Figure 46.4, the Chinook salmon is the apex consumer at the top of this food chain. | B: primary consumers. |
What is the term for a period when temperatures are cooler than normal causing glaciers to spread to lower latitudes?
Here are the choices:
A. cooling era
B. ice age
C. cold age
D. freezing point | But ice ages also occurred many times in the past. An ice age is a period when temperatures are cooler than normal. This causes glaciers to spread to lower latitudes. Scientists think that ice ages occurred at least six times over the last billion years alone. How do scientists learn about Earth’s past climates?. | B: ice age. |
Cody's velocity is zero so therefore he doesn't have what?
Here are the choices:
A. momentum
B. weight
C. mass
D. temperature | A : Cody has no momentum as he stands there because he isn’t moving. In other words, his velocity is zero. However, Cody will gain momentum as he starts moving down the ramp and picks up speed. | A: momentum. |
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