RISE Science — Grade 8

A student pours 50 mL of vinegar into a flask and adds 10 g of baking soda. She immediately seals the flask with a tight rubber stopper. A gas forms and inflates a balloon attached to the flask. When she measures the total mass of the sealed apparatus before and after the reaction, the mass remains exactly 160 grams. Which principle does this phenomenon demonstrate?

• AGas molecules have no mass when produced in a reaction.
• BTotal mass is conserved in a closed system during a chemical reaction.
• CChemical reactions create new matter that replaces the original reactants.
• DEnergy is converted into mass when bubbles are generated.

An iron nail with a mass of 5.0 grams is left in a humid environment for several weeks. When re-weighed, the rusty nail has a mass of 5.7 grams. Why did the mass of the solid nail increase?

• AIron atoms multiplied inside the nail due to exposure to water.
• BOxygen gas from the surrounding air chemically bonded with iron atoms to form rust.
• CThe nail absorbed heat energy which added extra mass to the solid metal.
• DRust is denser than pure iron, so the nail gained weight without adding atoms.

A block of solid dry ice (carbon dioxide) is placed on a table at room temperature. White foggy gas immediately begins billowing off the block, and after one hour no solid remains. Which statement correctly describes this event?

• AIt is a chemical reaction because a new gas substance with different properties was creat…
• BIt is a physical change (sublimation) because the carbon dioxide molecules changed state…
• CIt is a chemical change because carbon dioxide atoms disappeared permanently.
• DIt is a physical change because the total mass of the room decreased.

A hiker activates an instant hand warmer pouch by squeezing it to mix iron powder, water, and salt. Within minutes, the pouch feels warm to the touch. What type of reaction is occurring inside the pouch?

• AAn endothermic chemical reaction that absorbs thermal energy from the hiker's hands.
• BAn exothermic chemical reaction that releases stored chemical energy as thermal energy.
• CA physical phase change where liquid water freezes into solid ice.
• DA nuclear reaction that converts iron atoms into helium gas.

An athletic trainer snaps an instant cold pack to mix water and solid ammonium nitrate. The cold pack quickly drops in temperature from 22°C to 4°C. How should this phenomenon be classified?

• AAn exothermic reaction because thermal energy is destroyed.
• BAn endothermic process because thermal energy is absorbed from the surroundings.
• CA physical change because no energy transfer took place.
• DAn exothermic reaction because cold energy is released into the skin.

When methane gas (CH4) reacts with oxygen gas (2O2), it forms carbon dioxide (CO2) and water vapor (2H2O). Which statement about the atoms in this reaction is correct?

• AThe total number of hydrogen atoms increases from 4 to 8 during combustion.
• BCarbon atoms are converted into oxygen atoms to release heat.
• CThe exact same number of carbon, hydrogen, and oxygen atoms exist before and after the re…
• DOxygen atoms disappear completely to create new water molecules.

Plastic water bottles are made from polyethylene, a synthetic polymer synthesized from natural petroleum oil. Which statement best explains how synthetic materials differ from the natural resources used to make them?

• ASynthetic materials contain atoms that do not exist in nature.
• BSynthetic materials are created through human chemical processing that rearranges natural…
• CNatural resources cannot undergo chemical reactions unless synthetic chemicals are added.
• DSynthetic materials return to their natural oil state instantly when exposed to sunlight.

During summer at Utah's Great Salt Lake, shallow water evaporates under intense sunlight, leaving thick white crusts of solid salt along the shoreline. What process is occurring to form the salt crust?

• AA chemical reaction that synthesizes salt out of hydrogen and oxygen gas.
• BA physical separation where liquid water changes to gas, leaving dissolved mineral ions b…
• CAn endothermic chemical reaction that turns water molecules into sodium chloride.
• DA chemical change where sunlight breaks salt bonds into water vapor.

A shiny copper statue exposed to outdoor air over decades slowly turns bright green. Scientists test the green coating and find it is copper carbonate. What evidence confirms a chemical reaction occurred?

• AThe copper metal dissolved into a transparent liquid state.
• BA new substance with a different color and chemical composition was formed from copper, o…
• CThe mass of the statue decreased to zero as copper atoms transformed into energy.
• DThe statue absorbed light waves and reflected green light without any atomic changes.

A campfire burns a 10 kg wooden log inside an open fire pit. Afterwards, the remaining pile of ash weighs only 0.5 kg. Does this observation violate the Law of Conservation of Mass?

• AYes, because 9.5 kg of wood mass was destroyed by high heat.
• BNo, because the remaining 9.5 kg escaped into the air as carbon dioxide, water vapor, and…
• CYes, because chemical reactions in open fires do not follow mass conservation rules.
• DNo, because ash particles are 20 times denser than original wood atoms.

A student combines two clear liquid solutions in a beaker. Immediately, the liquid turns milky white and solid particles sink to the bottom. What key indicator shows that a chemical reaction took place?

• AThe liquid expanded to fill the entire classroom.
• BA insoluble solid precipitate formed from the reaction of dissolved ions.
• CThe total number of atoms in the beaker doubled upon mixing.
• DOne of the liquids boiled away into a vacuum.

When a light stick (glow stick) is bent, an inner glass capsule breaks, allowing two liquids to mix. The stick begins to glow brightly, but its temperature does not change. What is occurring inside the stick?

• AA physical change where liquid molecules release stored friction heat.
• BA chemical reaction (chemiluminescence) that releases energy in the form of light.
• CA nuclear decay reaction where hydrogen turns into glow particles.
• DAn endothermic reaction that absorbs light from the room to look bright.

A beaker of liquid water at 20°C is placed on a hot plate. As thermal energy is added, the water temperature increases to 100°C and starts boiling. How does this energy transfer affect the water particles?

• AThe particles slow down and pack more tightly together.
• BThe particles gain kinetic energy, move faster, and break attractive forces to become ste…
• CThe water molecules split into separate hydrogen and oxygen gas atoms.
• DThe mass of each individual water particle decreases by half.

Engineers developed synthetic Kevlar fabric for body armor by reacting petroleum-derived chemicals to form long repeating chains of molecules. Why does Kevlar have properties distinct from natural petroleum?

• APetroleum contains non-existent elements that activate during manufacturing.
• BChemical reactions linked small monomer molecules into strong repeating polymer structure…
• CKevlar is a physical mixture of liquid oil and ground-up steel fibers.
• DSynthetic processes remove all chemical bonds so the material cannot burn.

A hydrogen fuel cell vehicle combines hydrogen gas (H2) and oxygen gas (O2) to generate electricity, producing pure water (H2O) as the only exhaust. Which statement best models this reaction?

• AHydrogen atoms are destroyed to generate clean water.
• BReactant gas molecules break apart and their atoms rearrange to form water molecules.
• COxygen gas condenses into a liquid without undergoing any chemical bonding.
• DElectricity converts water into hydrogen and oxygen reactants inside the exhaust pipe.

A student places an antacid tablet and a small beaker of water inside a sealable plastic ziplock bag. The initial mass of the entire system on a digital scale is 124.5 grams. The student drops the tablet into the water and quickly zips the bag closed. Bubbles fizz rapidly and the bag inflates. What will the digital scale read after the fizzing stops?

• ALess than 124.5 grams because gas has no mass.
• BExactly 124.5 grams because the system remained closed and matter was conserved.
• CMore than 124.5 grams because the inflated bag occupies more volume.
• D0.0 grams because chemical energy replaced all the mass.

Plant leaves absorb sunlight, water (H2O), and carbon dioxide (CO2) to produce glucose sugar (C6H12O6) and oxygen gas (O2). How is energy involved in this process?

• AIt is an endothermic process where solar energy is absorbed and stored as chemical energy…
• BIt is an exothermic process where plants release heat to warm the surrounding atmosphere.
• CEnergy is converted into carbon atoms to construct new leaf tissue.
• DNo energy change occurs because plants are non-living structures.

Water (H2O) exists as discrete molecules containing two hydrogen atoms bonded to one oxygen atom. In contrast, quartz mineral (SiO2) forms an extended 3D crystal lattice. How do these two molecular structures compare?

• AWater molecules form continuous unbroken solid grids at room temperature, while quartz is…
• BWater consists of individual independent molecular units, while quartz consists of an int…
• CQuartz contains no chemical bonds, whereas water is held together entirely by gravity.
• DBoth water and quartz have identical physical hardness and melting points.

A solid brass sphere barely fits through a metal ring at room temperature. After heating the sphere over a burner for 2 minutes, it no longer fits through the ring. What happened at the particle level?

• AThe copper and zinc atoms in brass expanded in mass.
• BThermal energy increased particle vibration, pushing adjacent atoms slightly farther apar…
• CA chemical reaction added new carbon atoms into the brass structure.
• DThe heat caused the metal ring to shrink around the cold sphere.

A baker mixes yeast, warm water, and sugar into bread dough. After sitting in a warm bowl for an hour, the dough doubles in size and exhibits small air pockets throughout. What evidence shows a chemical reaction occurred?

• ASugar melted into liquid water without any chemical change.
• BYeast cells consumed sugar and chemically produced carbon dioxide gas bubbles that expand…
• CThe water molecules transformed into solid flour particles.
• DThe total weight of the bread dough tripled automatically.

Scientists engineered a bio-based synthetic plastic derived from cornstarch that decomposes in soil within 90 days, compared to conventional petroleum plastic which persists for centuries. What structural feature allows bio-plastic to decompose faster?

• ABio-plastic contains no chemical bonds between its atoms.
• BSoil microbes possess enzymes capable of breaking the specific chemical ester bonds in bi…
• CBio-plastic turns into pure energy when exposed to dirt.
• DPetroleum plastics are held together by nuclear forces that cannot be broken.

In a closed laboratory chamber, 32 grams of solid sulfur reacts completely with 32 grams of oxygen gas to form sulfur dioxide gas (SO2). Based on the Law of Conservation of Mass, what is the exact mass of sulfur dioxide produced?

• A16 grams
• B32 grams
• C64 grams
• D128 grams

A student monitors two different chemical reactions in insulated thermoses: - Reaction A: Initial temp = 22°C, Final temp = 14°C - Reaction B: Initial temp = 22°C, Final temp = 38°C Which conclusion correctly compares the energy changes in Reaction A and Reaction B?

• ABoth reactions are exothermic because temperature changed in both thermoses.
• BReaction A is endothermic (absorbed thermal energy) and Reaction B is exothermic (release…
• CReaction A is exothermic and Reaction B is endothermic.
• DReaction A destroyed energy while Reaction B created energy.

Sodium chloride (NaCl) solid has a melting point of 801°C, whereas methane gas (CH4) has a melting point of -182°C. How do their underlying chemical structures account for this vast difference in physical properties?

• ANaCl forms a 3D ionic lattice with strong continuous electrostatic bonds, while CH4 consi…
• BCH4 forms an extended metallic crystal lattice, while NaCl is a single diatomic gas molec…
• CNaCl molecules contain no chemical bonds, allowing them to freeze instantly.
• DCH4 contains heavier atoms that cause it to evaporate at extremely cold temperatures.

An engineering team is designing a reusable hand warmer pouch containing supersaturated sodium acetate solution. Flexing a metal disk inside triggers rapid crystallization of the liquid into solid crystals, raising the pouch temperature to 54°C. How can the pouch be reset to its liquid state for reuse?

• ACool the solid pouch in a freezer to absorb cold energy.
• BBoil the pouch in hot water to input thermal energy, breaking crystal lattice bonds and r…
• CExpose the pouch to pure nitrogen gas to destroy the sodium atoms.
• DShake the pouch vigorously to create nuclear friction.

A geranium plant sits on a sunny windowsill. Over several weeks it grows noticeably larger and heavier, yet the mass of soil in its pot barely changes. Where does the great majority of the plant's added mass come from?

• AMinerals drawn up out of the potting soil
• BCarbon dioxide taken in from the air, combined with water
• CSunlight, which is converted directly into solid plant tissue
• DOxygen absorbed through the roots during the night

Which statement correctly identifies the reactants and products of photosynthesis?

• ACarbon dioxide and water are reactants; glucose and oxygen are products
• BGlucose and oxygen are reactants; carbon dioxide and water are products
• COxygen and water are reactants; carbon dioxide and glucose are products
• DCarbon dioxide and glucose are reactants; water and oxygen are products

A student runs a mile and breathes hard afterward, exhaling carbon dioxide and water vapor. Which process inside the student's cells produced those exhaled substances?

• APhotosynthesis, which stores energy in sugar molecules
• BCellular respiration, which breaks down glucose to release stored energy
• CEvaporation of water from the surface of the lungs
• DDigestion, which physically grinds food into smaller pieces

In a Utah rangeland food web, energy moves from cheatgrass to grasshoppers to sage thrashers to kestrels. What is the original source of the energy moving through this whole food web?

• ASunlight captured by the cheatgrass
• BMinerals in the desert soil
• CHeat released by the grasshoppers
• DWater stored in the plants' tissues

Fungi and bacteria break down a fallen cottonwood log on the forest floor over many years. What is their most important role in the cycling of matter in this ecosystem?

• AThey convert sunlight into chemical energy for other organisms
• BThey return carbon and nutrients from dead tissue to the soil and air for reuse
• CThey permanently remove carbon atoms from the ecosystem
• DThey create brand-new atoms that replace the ones lost from the log

Which cell structure is the site where light energy is captured and used to build sugar molecules?

• AMitochondrion
• BChloroplast
• CCell membrane
• DNucleus

A sealed terrarium holds a small plant, moist soil, and air, and receives daily sunlight for six months. The total mass of the sealed terrarium is measured at the start and again at the end. What should the measurements show, and why?

• AThe mass increases, because the plant creates new matter as it grows
• BThe mass decreases, because the plant consumes carbon dioxide
• CThe mass stays the same, because atoms are only rearranged among the plant, air, soil, an…
• DThe mass stays the same, because no chemical reactions occur inside a sealed container

A student eats a slice of bread. Which statement best describes what happens to the atoms in the starch molecules of that bread?

• AThey are destroyed to release the energy stored in the food
• BThey are broken apart and rearranged into new molecules that build tissue or are released…
• CThey pass through the body unchanged and are excreted
• DThey are converted directly into pure energy with no matter remaining

Which sequence correctly traces a single carbon atom through the carbon cycle?

• ACarbon dioxide in air → sugar in a plant → tissue in a deer → carbon dioxide released by…
• BSugar in a plant → sunlight → carbon dioxide in air → mineral in soil
• CCarbon dioxide in air → oxygen gas → water in a lake → sugar in a plant
• DTissue in a deer → sunlight → sugar in a plant → carbon dioxide in air

A wetland food chain near the Great Salt Lake runs from algae to brine shrimp to eared grebes. Why can the wetland support far fewer grebes than brine shrimp?

• AGrebes need less food than brine shrimp do
• BMost of the energy at each level is used for life processes or lost as heat, so less is a…
• CMatter is destroyed each time one organism eats another
• DBrine shrimp reproduce more slowly than grebes do

Wolves were removed from a mountain valley. Elk numbers then rose sharply, and young aspen and willow shoots along the streams were eaten faster than they could regrow. Which statement best explains the effect on the ecosystem?

• ARemoving one species has no measurable effect on how matter and energy move through an ec…
• BLosing a predator changed the flow of energy and the cycling of matter well beyond the el…
• CThe valley now cycles matter faster because there are more elk
• DEnergy stopped flowing through the valley once the wolves were gone

How are photosynthesis and cellular respiration related to each other?

• ABoth processes store energy in glucose molecules
• BThe products of one process are the reactants of the other
• CBoth processes release oxygen into the atmosphere
• DOnly plants carry out photosynthesis and only animals carry out cellular respiration

A farmer plows crop residue back into a field each autumn instead of burning it. How does this practice affect the cycling of matter in the field?

• AIt removes carbon and nutrients from the field permanently
• BIt allows decomposers to return carbon and nutrients to the soil, where plants can use th…
• CIt prevents any chemical reactions from occurring in the soil
• DIt creates new nutrient atoms that were not present before

A student wants to test whether light intensity affects the rate of photosynthesis in an aquatic plant. She plans to count the oxygen bubbles released per minute at different distances from a lamp. Which variable must she hold constant for the results to be valid?

• AThe distance between the lamp and the plant
• BThe number of bubbles counted each minute
• CThe water temperature in the container
• DThe intensity of the light reaching the plant

A calf drinks milk and gains 40 kilograms over several months. Which statement best explains where that added body mass came from?

• AThe energy in the milk was converted into solid body mass
• BAtoms from the milk molecules were rearranged and built into new muscle, bone, and other…
• CThe calf produced new atoms as it matured
• DThe added mass came entirely from the water the calf drank

A large section of forest is cleared and paved. Which effect on the local carbon cycle is most direct?

• ALess carbon dioxide is removed from the air because fewer producers remain to photosynthe…
• BCarbon atoms in the area are permanently destroyed
• CDecomposers immediately stop functioning throughout the region
• DThe total number of carbon atoms on Earth decreases

The overall equation for photosynthesis is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. A plant incorporates 264 grams of carbon dioxide and 108 grams of water into this reaction. Assuming the reaction goes to completion, what is the combined mass of the glucose and oxygen produced?

• A156 grams
• B264 grams
• C372 grams
• DIt cannot be determined without knowing the light intensity

Producers in a meadow store 20,000 kilocalories of energy. If roughly 10 percent of the energy at each level is stored as new tissue at the next, about how much energy is available to store in the tissue of secondary consumers?

• A2,000 kilocalories
• B200 kilocalories
• C20 kilocalories
• D18,000 kilocalories

Fertilizer runoff enters a reservoir, algae grow explosively, and when the algae die, decomposer bacteria multiply rapidly. Fish are later found dead. Which explanation best connects these observations?

• AThe algae released a toxin that poisoned the fish directly
• BDecomposers consumed large amounts of dissolved oxygen as they broke down the dead algae,…
• CThe fertilizer atoms were destroyed, removing nutrients the fish needed
• DThe extra algae blocked the fish from reaching the surface to breathe air

A sealed, transparent chamber holds a healthy plant and a small cricket. The chamber is kept in continuous darkness for two days. What is the most likely outcome, and why?

• ABoth organisms thrive, because the plant supplies oxygen continuously
• BOxygen levels fall and carbon dioxide rises, because in darkness both organisms respire b…
• COxygen levels rise, because plants release the most oxygen at night
• DThe total mass inside the chamber decreases as oxygen is used up

Utah has large copper deposits near Bingham Canyon but almost none in other parts of the state. What best explains why mineral resources are spread unevenly across Earth?

• AMinerals form wherever people choose to dig for them
• BSpecific geologic processes, such as magma activity and hydrothermal fluids, concentrate…
• CMinerals are distributed evenly but are easier to see in mountains
• DMineral deposits move slowly across Earth's surface over time

Which of the following is classified as a nonrenewable resource?

• AWind used to turn turbines
• BSunlight collected by solar panels
• CNatural gas extracted from underground rock
• DTimber grown on a replanted tree farm