Tüm alıştırma soruları

Two scientists discuss the behavior of a newly discovered gas at high pressures.

Scientist 1
At high pressures, the gas molecules attract each other, causing the measured volume to be smaller than the volume predicted by the ideal gas law. These attractive forces only become significant at pressures above $10\text{ atm}$.

Scientist 2
At high pressures, the gas molecules repel each other, causing the measured volume to be larger than the volume predicted by the ideal gas law. These repulsive forces only become significant at pressures above $10\text{ atm}$.

Based on the descriptions, both Scientist 1 and Scientist 2 agree with which of the following statements regarding the gas?

Heat Source of Enceladus

Saturn's moon Enceladus has a liquid water ocean beneath its icy outer crust. Because Enceladus is far from the Sun, it receives very little solar energy. Two scientists discuss the primary source of the thermal energy that keeps this subsurface ocean liquid.

Scientist 1
The subsurface ocean is kept warm primarily by tidal heating. As Enceladus orbits Saturn in an elliptical path, the gravitational pull of Saturn and the neighboring moon Dione varies, causing Enceladus to repeatedly stretch and compress. This continuous deformation generates friction within the moon's interior, converting orbital energy into heat. This tidal heating is sufficient to prevent the ocean from freezing.

Scientist 2
The subsurface ocean is kept warm primarily by radiogenic heating (decay of radioactive elements). Enceladus's rocky core contains radioactive isotopes such as uranium, thorium, and potassium. The decay of these isotopes releases a steady supply of heat that warms the core and the ocean above it. Tidal forces are far too weak to generate the amount of heat required to maintain a liquid ocean over billions of years.

Both Scientist 1 and Scientist 2 share which of the following underlying assumptions?

A student investigates how the temperature of carbonic acid ($H_2CO_3$) affects the chemical weathering of basalt. The student hypothesizes that as the temperature of the acid solution increases, the rate of chemical weathering (measured as the mass of basalt dissolved over a 24-hour period) will increase. The student performs four trials, starting with a $50.0\text{ g}$ sample of basalt in each trial, while keeping the acid volume and concentration constant. The results are shown in the table below:

Based on the student's hypothesis, if a fifth trial were conducted at $55^\circ\text{C}$ under the same conditions, what would be the predicted final mass of the basalt sample?

Two models are proposed to explain the heat source maintaining the liquid water ocean beneath the icy crust of Saturn's moon, Enceladus.

Tidal Heating Model
Orbital resonance with other moons causes gravitational tidal flexing of Enceladus's rocky core. This flexing generates significant frictional heat concentrated in the core, maintaining core temperatures above $1000^\circ\text{C}$ and driving high-temperature hydrothermal activity at the core-ocean boundary.

Radioactive Decay Model
The primary heat source is the decay of radioactive isotopes within the core. This decay produces a low-intensity, uniform heat flux. Because radioactive isotopes have decayed over billions of years, current core temperatures are predicted to be low, not exceeding $200^\circ\text{C}$.

Spacecraft measurements detect silica ($SiO_2$) nanoparticles in the plumes erupting from Enceladus's south polar fractures. Laboratory experiments demonstrate that these nanoparticles can only form when liquid water interacts with rock at temperatures of at least $800^\circ\text{C}$.

Which of the following statements best describes how this finding relates to the two models?

A student hypothesized that as the concentration of salt ($\text{NaCl}$) dissolved in water increases, the boiling point of the water decreases. To test this, the student added different masses of $\text{NaCl}$ to $100\text{ mL}$ of pure water and recorded the boiling point of each solution. The results are shown in the table below:

Based on these results, how should the student modify their hypothesis?

To investigate the factors affecting the rate of a chemical reaction, researchers conducted two experiments measuring the rate of decomposition of nitrogen dioxide ($NO_2$) into nitrogen monoxide ($NO$) and oxygen ($O_2$):

Experiment 1
Researchers introduced $1.0\text{ mol}$ of $NO_2$ gas into four separate rigid 10-liter containers at different temperatures. No other gases were initially present. The reaction rate was measured at the start of the reaction (initial rate). The results are shown in Table 1.

Experiment 2
Using Container 1 ($25^\circ\text{C}$), researchers repeated the reaction but added different amounts of helium ($He$), an inert gas that does not participate in the reaction, to test whether the total pressure of the container affects the reaction rate. The initial concentration of $NO_2$ was kept at $0.10\text{ mol/L}$ ($1.0\text{ mol}$ in the 10-liter container) in all trials. The results are shown in Table 2.

Based on the results of Experiments 1 and 2, which of the following setups serves as the control group to determine the effect of adding helium gas on the initial reaction rate in Experiment 2?

### Deep-Focus Earthquakes

Deep-focus earthquakes occur at depths between $300\text{ km}$ and $700\text{ km}$ below Earth's surface. At these depths, high pressures and temperatures should theoretically cause mantle rocks to deform ductilely (flowing like a highly viscous liquid) rather than fracturing brittlely. Three geophysicists propose different mechanisms to explain how deep-focus earthquakes can occur.

Geophysicist 1
Deep-focus earthquakes are triggered by *dehydration embrittlement*. Subducting tectonic slabs carry hydrous minerals, such as serpentine, deep into the mantle. Past a depth of $300\text{ km}$, the increasing temperature and pressure cause these minerals to destabilize and dehydrate, releasing high-pressure water. This fluid pressure offsets the confining pressure of the mantle, reducing the friction along faults and allowing sudden brittle failure. For this process to occur, hydrous minerals must survive to these depths, which requires the slab core to remain relatively cool, below $600^\circ\text{C}$. If the slab core temperature exceeds $600^\circ\text{C}$, dehydration occurs prematurely at shallower depths, and deep-focus earthquakes will not occur.

Geophysicist 2
Deep-focus earthquakes are caused by *transformational faulting* (anticrack shear) of metastable olivine. As a cold slab subducts rapidly, the olivine in its core remains metastable past its normal stability depth. At depths of $350\text{ km}$ to $700\text{ km}$, this metastable olivine undergoes a rapid phase transition to the high-pressure polymorphs wadsleyite or ringwoodite. Under shear stress, this transition initiates along thin, localized bands. The volume decrease associated with the phase change causes structural collapse and localized shear heating, leading to a runaway slip event. This mechanism requires the presence of metastable olivine, which can only survive in subducting slab cores that remain below $700^\circ\text{C}$. At temperatures of $700^\circ\text{C}$ or higher, olivine transforms to its high-pressure phases under equilibrium conditions without generating sudden shear instability.

Geophysicist 3
Deep-focus earthquakes are caused by a *thermal runaway* instability. When subducting slabs deform under high shear stress, the mechanical energy is converted into heat. Because silicate rocks are poor conductors of heat, this thermal energy cannot dissipate quickly, raising the local temperature of the shear zone. Since rock viscosity decreases exponentially with temperature, this heating softens the rock, localizing the deformation further and generating even more heat. This positive feedback loop leads to thermal runaway and sudden shear slip. This mechanism can only initiate if the slab's core is cold enough (below $800^\circ\text{C}$) to support the high initial shear stresses necessary to trigger thermal runaway. In slabs with core temperatures at or above $800^\circ\text{C}$, the rock is too ductile to support high shear stresses, preventing the initiation of thermal runaway.

Based on the descriptions provided, all three geophysicists would agree that deep-focus earthquakes are unlikely to occur within a subducting slab if the slab's core temperature is:

A biochemist investigated the catalytic activity of amylase extracted from *Geobacillus stearothermophilus* at $70^\circ\text{C}$ in the presence of various divalent metal ions ($\text{Mg}^{2+}$, $\text{Ca}^{2+}$, $\text{Zn}^{2+}$, and $\text{Cu}^{2+}$). Five test tubes were prepared as shown in the table below. Each tube contained $1.0\text{ mL}$ of a $1\%$ starch solution, $1.0\text{ mL}$ of buffer solution ($\text{pH } 7.0$), and $0.1\text{ mL}$ of purified amylase enzyme.

All five tubes were incubated at $70^\circ\text{C}$ for 15 minutes, after which the rate of starch hydrolysis was determined for each tube.

Which of the following test tubes served as the control group to establish the baseline rate of starch hydrolysis in the absence of added metal ions?

### Ultra-Low Velocity Zones (ULVZs)

Ultra-Low Velocity Zones (ULVZs) are thin patches of rock at the Earth's core-mantle boundary (CMB), approximately $2,900\text{ km}$ below the surface, where seismic wave velocities drop by up to $30\%$. Three geophysicists present competing hypotheses regarding the composition and physical state of ULVZs.

Geophysicist 1
ULVZs are regions of partial melting of the lower mantle silicate rock. As hot, iron-rich mantle plumes rise from the CMB, localized temperatures exceed the solidus (melting temperature) of the silicate mineral post-perovskite. Silicate melt is denser than solid mantle minerals at CMB pressures, causing the melt to drain downward and accumulate at the CMB. This liquid phase significantly reduces the velocity of both compressional ($P$-waves) and shear ($S$-waves) seismic waves.

Geophysicist 2
ULVZs are solid, iron-enriched zones formed by chemical reactions between the liquid iron outer core and the solid silicate mantle. Liquid iron from the outer core leaks upward into the lower mantle through capillary action, reacting with silicate minerals to form iron-rich post-perovskite and iron oxides. Because iron has a high atomic mass, this enrichment increases the density of these zones relative to the surrounding mantle, causing a drastic reduction in seismic wave velocities without requiring any melting.

Geophysicist 3
ULVZs represent remnants of Earth's early magma ocean. During Earth's differentiation, heavy elements and iron-rich mineral phases sunk to the bottom of the magma ocean. As the mantle crystallized from the bottom up, a dense, iron-rich silicate slurry remained trapped at the CMB. These ancient, solid, chemically distinct reservoirs have remained stable at the CMB for billions of years due to their high density relative to the rest of the mantle.

Based on the passage, all three geophysicists would agree with which of the following statements regarding ULVZs?

### Passage

Coral Bleaching Mechanisms

Coral bleaching occurs when coral polyps expel the symbiotic algae (*Symbiodinium*) living in their tissues, turning the coral completely white. Three scientists discuss the primary driver of this phenomenon.

Scientist 1
Coral bleaching is primarily triggered by elevated sea surface temperatures (SST). When SST exceeds the local summer maximum by $1^\circ\text{C}$ or more, thermal stress disrupts the photosynthetic pathways of the algae, producing toxic reactive oxygen species. To survive, the coral host must expel the algae. While increased solar radiation (UV exposure) can exacerbate bleaching, elevated temperature is the essential and direct cause of the algal expulsion.

Scientist 2
The primary driver of coral bleaching is ocean acidification, not thermal stress. As atmospheric $\text{CO}_2$ dissolves in oceans, seawater pH declines. The reduced availability of carbonate ions stresses the coral’s calcification process, destabilizing the cellular connection between the host and the algae. Elevated sea surface temperature is not the direct trigger; rather, warmer water increases the metabolic rate of the coral, which accelerates the bleaching process only after acidification has already weakened the coral host (when pH falls below $7.9$).

Scientist 3
Coral bleaching is an infectious disease process caused by opportunistic bacterial pathogens, such as *Vibrio coralliilyticus*. These bacteria are abundant in marine environments but only become virulent at higher temperatures. Under normal conditions, the coral's immune system prevents infection. However, elevated sea surface temperatures suppress the coral’s immune response and increase bacterial toxin production, leading to infection and subsequent algal expulsion. Thus, elevated temperature is a necessary environmental catalyst, but bacterial infection is the direct cause of bleaching.

Question

Based on the passage, all three scientists would agree with which of the following statements regarding the role of elevated sea surface temperatures in coral bleaching?

Three models are proposed to explain the formation of hematite ($\text{Fe}_2\text{O}_3$) spherules, commonly called "blueberries," discovered in the Meridiani Planum region of Mars.

*Model 1*
Spherules formed in situ within porous basaltic volcanic rock. Upwelling volcanic fluids heated to temperatures between $150^\circ\text{C}$ and $250^\circ\text{C}$ circulated through underground aquifers. These fluids, neutral in pH and rich in dissolved iron, encountered sudden pressure drops, causing hematite to precipitate symmetrically in all directions within spherical pore spaces (vesicles). Because the vesicles were free of mineral grains, the resulting spherules consist of pure, crystalline hematite with no internal sedimentary inclusions.

*Model 2*
Spherules formed as chemical concretions in a shallow, highly acidic ($pH < 3.0$), hypersaline surface lake. Liquid water containing dissolved $\text{Fe}^{3+}$ ions seeped downward through porous quartz sandstone. The acidic water reacted with localized, alkaline carbonate minerals within the sandstone, raising the pH and causing hematite to precipitate outward from nucleation centers. Consequently, these spherules grew around and enveloped surrounding quartz sand grains, resulting in a concentric internal structure containing micro-grains of quartz.

*Model 3*
Spherules are impact spherules created during a hypervelocity meteorite impact on the Martian surface. The impact vaporized iron-rich basaltic target rocks and the iron-nickel meteorite itself, ejecting a plume of vapor and molten droplets into the upper atmosphere. As the droplets fell back toward the surface, they cooled and solidified into spherical shapes. The spherules accumulated as a distinct, widespread air-fall layer on top of preexisting rock units, rather than growing within them.

Match each description of a spherule's formation mechanism or physical constraint to the specific model that proposes it.

### Passage
An agricultural biologist investigated the physiological stress responses of the green alga *Chlorella vulgaris* exposed to common components of agricultural runoff. The study focused on four environmental variables: nitrate ($NO_3^-$) enrichment, phosphate ($PO_4^{3-}$) enrichment, atrazine (a widely used herbicide) exposure, and elevated temperature.

The biologist set up 5 culture flasks with identical initial densities of *C. vulgaris*. Each flask was subjected to a specific combination of nutrient concentrations, atrazine concentration, and temperature for 7 days. The experimental conditions for each flask are detailed in Table 1.

To evaluate the specific, independent contribution of each variable or combination of variables to algal stress, the biologist must compare the growth rates of algae in the experimental flasks against their appropriate control groups or baseline conditions.

### Matching Task
Match each of the following experimental objectives with the specific Flask that serves as its primary control group or baseline condition.

A research team investigated the photoelectrochemical (PEC) water-splitting efficiency of a bismuth vanadate ($BiVO_4$) photoanode. The experimental apparatus consisted of a three-electrode PEC cell connected to a potentiostat. The working electrode (photoanode) was illuminated by a simulated solar light source equipped with an Air Mass (AM) 1.5G filter and a water-filled optical filter. The electrochemical cell contained a $0.5\text{ M } Na_2SO_4$ aqueous electrolyte. A platinum ($Pt$) wire counter electrode was used to complete the circuit, and a silver/silver chloride ($Ag/AgCl$) electrode served as the reference. The gaseous products evolved at the electrodes were swept by an inert carrier gas into a gas chromatograph for quantification.

Match each component of the experimental apparatus to its primary function in this experimental setup.

### Passage I

Researchers investigated the regulation of the electron transport chain (ETC) in isolated mammalian mitochondria by measuring the rate of oxygen ($O_2$) consumption (in $\text{nmol } O_2/\text{min}/\text{mg protein}$) under different biochemical conditions.

In all trials, a fixed concentration of isolated mitochondria was suspended in a reaction chamber containing a physiological buffer solution at $37^\circ\text{C}$. The baseline concentration of dissolved $O_2$ in the buffer was monitored. Respiration substrates, adenylates, and metabolic inhibitors were added sequentially or in combination to study their effects on the rate of mitochondrial $O_2$ consumption. The components added to each trial are shown in Table 1.

### Table 1

An investigator wants to establish a baseline condition to prove that the decrease in dissolved $O_2$ in Trials 1–5 is due to the biological activity of the electron transport chain in the mitochondria, rather than abiotic chemical reactions or gas leakage from the reaction chamber. Which of the trials listed in Table 1 serves as the most appropriate control group for this purpose?

A student proposed the following hypothesis:
*Hypothesis*: As the temperature of water increases from $0^\circ\text{C}$ to $10^\circ\text{C}$, the density of the water will decrease continuously, and this density decrease will be more pronounced in water with higher salinity.

To test this hypothesis, the student measured the density of freshwater ($0\text{ ppt}$ salinity) and saline water ($10\text{ ppt}$ salinity) at different temperatures. The results are shown in the table below.

Based on these results, how should the student modify the hypothesis regarding the relationship between temperature, salinity, and density?

Two scientists discuss the conditions necessary for the rusting of iron ($Fe$).

Scientist 1
Rusting is a chemical reaction that requires only iron and oxygen ($O_2$) gas. When iron is exposed to $O_2$, it reacts to form iron oxide (rust). Water ($H_2O$) is not necessary for this reaction to occur.

Scientist 2
Rusting is a chemical reaction that requires only iron and liquid water ($H_2O$). When iron is exposed to $H_2O$, it reacts to form rust. Oxygen ($O_2$) gas is not necessary for this reaction to occur.

Which of the following experiments would best determine which scientist's viewpoint is correct?

### Solar Coronal Heating

The temperature of the solar corona (the Sun's outer atmosphere) is millions of kelvins ($\text{K}$), which is significantly hotter than the photosphere (the solar surface), which is only about $5,800\text{ K}$. Three hypotheses are proposed to explain how energy is transported from the photosphere and dissipated in the corona.

Wave Heating Hypothesis
Coronal heating is caused by magnetohydrodynamic (MHD) waves, specifically Alfvén waves. Convective motions of plasma in the photosphere continuously perturb magnetic field lines. This perturbation generates Alfvén waves that propagate upward along the magnetic field lines into the corona. The magnetic field acts as a waveguide, transporting this wave energy. Once in the corona, these waves undergo reflection and dissipation due to the low density of the coronal plasma, transferring their energy to the corona as thermal energy.

Nanoflare Hypothesis
Coronal heating is caused by magnetic reconnection. The convective motions of plasma in the photosphere twist and braid coronal magnetic field lines. This slowly stores magnetic energy in the coronal magnetic field. When the magnetic stress reaches a threshold, the magnetic field lines abruptly reconnect, releasing this stored magnetic energy in millions of localized, miniature explosions called "nanoflares." These nanoflares convert magnetic energy directly into thermal energy, heating the coronal plasma.

Turbulent Dissipation Hypothesis
Convective motions of plasma in the photosphere launch low-frequency magnetic waves. As these waves travel along the magnetic field lines into the corona, they interact with waves reflected from the boundaries of the corona. This interaction generates magnetohydrodynamic (MHD) turbulence. The turbulence cascades the energy to progressively smaller spatial scales. At very small scales, kinetic effects dissipate the turbulent energy, heating the corona.

Based on the three hypotheses, match each scientific statement about coronal heating to the specific category of agreement or uniqueness that describes it.

Passage

Two biologists present competing hypotheses regarding the evolutionary origin of hydrogenosomes, double-membraned organelles found in certain anaerobic eukaryotes that produce molecular hydrogen ($H_2$).

Biologist 1
Hydrogenosomes evolved directly from an ancestral anaerobic endosymbiotic bacterium that was distinct from the aerobic $\alpha$-proteobacterium that gave rise to mitochondria. This ancestral endosymbiont belonged to an anaerobic lineage of bacteria that possessed hydrogenase enzymes. Over evolutionary time, this bacterium transferred most of its genome to the host nucleus, leaving an organelle specialized for anaerobic ATP production. Consequently, hydrogenosomes and mitochondria represent completely independent endosymbiotic events.

Biologist 2
Hydrogenosomes and mitochondria share a common endosymbiotic ancestor: a facultatively anaerobic $\alpha$-proteobacterium. Depending on the environmental pressures faced by the host eukaryotic lineage, this single ancestral organelle diverged. In aerobic environments, it evolved into mitochondria, retaining the electron transport chain. In strictly anaerobic environments, it lost the electron transport chain and evolved into hydrogenosomes. Thus, hydrogenosomes are highly modified mitochondria rather than the product of a separate endosymbiotic event.

Based on Biologist 1's hypothesis, if a newly discovered anaerobic eukaryote is found to contain hydrogenosomes that still retain a small genome, the genes in this organellar genome would be expected to share the greatest sequence similarity with the genes of which of the following groups?

### Passage
Heating of the Solar Corona

The solar corona—the outermost layer of the Sun’s atmosphere—is hot, with temperatures exceeding $1,000,000\text{ K}$, while the underlying photosphere is only about $5,800\text{ K}$. Two astrophysicists discuss competing models for how energy is transported and dissipated to heat the corona.

Astrophysicist 1
The corona is heated primarily by magnetohydrodynamic (MHD) waves, specifically Alfvén waves. These waves are generated by the mechanical motion of plasma in the convective zone and travel upward along magnetic field lines into the corona. Because the corona has an extremely low density, these waves become non-linear and dissipate, transferring kinetic energy directly to the coronal particles as heat. This wave propagation and dissipation process occurs continuously across the entire solar surface.

Astrophysicist 2
The corona is heated by thousands of small, discrete magnetic reconnection events called nanoflares. The turbulent motion of the photosphere twists and braids the magnetic field lines that extend into the corona. When the tension in these braided lines becomes too high, the magnetic fields rapidly snap and reconnect, releasing stored magnetic energy. This energy is converted into thermal energy, heating the local plasma. These reconnection events are localized and intermittent, but their high frequency across all magnetic loops accounts for the high coronal temperature.

Question
In order for Astrophysicist 1’s model of coronal heating to be valid, which of the following implicit assumptions must be true regarding the solar atmosphere between the convective zone and the corona?

### Ocean Acidification and Oysters

Two students discuss the effects of rising atmospheric carbon dioxide ($CO_2$) on marine organisms that build calcium carbonate ($CaCO_3$) shells.

Student 1
Rising atmospheric $CO_2$ dissolves in ocean water, lowering its pH and making it more acidic. This acidic water directly dissolves the existing $CaCO_3$ shells of living adult oysters, killing them. Therefore, the decline in oyster populations is driven by the chemical dissolution of their shells.

Student 2
Rising atmospheric $CO_2$ does lower ocean pH, but this does not dissolve existing shells. Instead, the lower pH reduces the concentration of carbonate ions ($CO_3^{2-}$) in the water. Larval oysters require these ions to construct their shells. Without sufficient carbonate ions, larval oysters cannot build shells and die before reaching adulthood. Thus, the population decline is driven by the inability of young oysters to build new shells.

Based on the passage, both Student 1 and Student 2 assume which of the following?