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VALID Science 8 practice questions

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Question 1Science

Which statement best describes what a scientific hypothesis must be?

  1. A personal opinion held by a scientist
  2. A description of an unexplained mystery
  3. A testable prediction based on observation Correct answer.
  4. A final conclusion that cannot be changed

Explanation

A hypothesis is a proposed explanation or prediction that can be tested through observation or experiment. Because it is testable, evidence can support or reject it, and scientists may revise it as new data appear. A hypothesis is therefore a starting tool for investigation rather than a fixed conclusion.

Question 2Science

A student measures the length of a leaf as 12.4 cm, 12.5 cm, and 12.4 cm. Which statement about these measurements is accurate?

  1. They are neither precise nor accurate
  2. They are accurate but not precise
  3. They are both accurate and imprecise
  4. They are precise but may not be accurate Correct answer.

Explanation

Precision refers to how close repeated measurements are to one another, while accuracy refers to how close they are to the true value. The three readings cluster tightly together, so they are precise. Without knowing the true length of the leaf, we cannot confirm their accuracy.

Question 3Science

Which change in state involves a substance gaining thermal energy?

  1. Deposition of vapor into frost
  2. Melting of ice into water Correct answer.
  3. Freezing of water into ice
  4. Condensation of steam into water

Explanation

When a solid melts, its particles gain energy and move more freely, so the substance absorbs thermal energy from its surroundings. Freezing, condensation, and deposition all release energy as particles become more ordered. Melting is therefore the process in which energy is gained.

Question 4Science

A pure element is best defined as a substance made of which of the following?

  1. Any material found in nature
  2. Two or more atoms chemically bonded
  3. Only one kind of atom Correct answer.
  4. A mixture of different molecules

Explanation

An element consists of only one type of atom, which cannot be broken down into simpler substances by chemical means. Compounds contain two or more elements chemically combined. Mixtures contain different substances that are not chemically bonded.

Question 5Science

In a chemical reaction, a sealed container holds reactants that combine to form a new product. What happens to the total mass inside the container?

  1. It decreases because a new product forms
  2. It increases because energy is released
  3. It changes unpredictably
  4. It stays the same Correct answer.

Explanation

The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction. Atoms are simply rearranged into new combinations, so the total mass of the closed system remains constant. In a sealed container nothing can enter or leave, so the mass does not change.

Question 6Science

Which process allows plants to convert light energy into chemical energy stored in glucose?

  1. Cellular respiration
  2. Transpiration
  3. Photosynthesis Correct answer.
  4. Digestion

Explanation

Photosynthesis uses light energy, carbon dioxide, and water to produce glucose and oxygen inside chloroplasts. The glucose stores chemical energy that organisms can later use. Cellular respiration does the reverse by releasing energy from glucose.

Question 7Science

A food chain begins with grass, then grasshoppers, then frogs, then snakes. Which organism is the primary consumer?

  1. Grasshopper Correct answer.
  2. Snake
  3. Grass
  4. Frog

Explanation

Primary consumers are organisms that eat producers directly. Grass is the producer, so the grasshopper that eats it is the primary consumer. Frogs and snakes occupy higher trophic levels as secondary or tertiary consumers.

Question 8Science

Which human body system is mainly responsible for transporting oxygen and nutrients to cells?

  1. Respiratory system
  2. Circulatory system Correct answer.
  3. Digestive system
  4. Skeletal system

Explanation

The circulatory system, including the heart, blood, and blood vessels, moves oxygen and nutrients throughout the body. The respiratory system brings oxygen into the body, but the circulatory system distributes it. The digestive system breaks down food, and the skeletal system provides support.

Question 9Science

A cell is placed in a container of pure water. Water moves into the cell, causing it to swell. Which statement explains this observation?

  1. The cell contains no dissolved substances
  2. The cell has a higher solute concentration than pure water Correct answer.
  3. The cell has a lower solute concentration than pure water
  4. The cell membrane blocks all water movement

Explanation

Osmosis is the movement of water across a membrane from an area of lower solute concentration to an area of higher solute concentration. Pure water has the lowest possible solute concentration, so water enters the cell if the cell's interior is more concentrated. This inflow causes the cell to swell.

Question 10Science

Which structure controls the activities of a eukaryotic cell and contains most of its genetic material?

  1. Nucleus Correct answer.
  2. Mitochondrion
  3. Cell membrane
  4. Vacuole

Explanation

The nucleus houses the cell's DNA and directs many cellular activities by regulating gene expression. The cell membrane controls what enters and leaves, mitochondria release energy, and vacuoles store materials. Only the nucleus contains the main genetic material in eukaryotic cells.

Question 11Science

A mutation occurs in a gene that codes for a protein. Which outcome is most likely if the mutation changes one DNA base?

  1. All other genes will stop working
  2. The organism will always die immediately
  3. The cell will lose all of its DNA
  4. The protein produced may have a different amino acid sequence Correct answer.

Explanation

A gene's base sequence determines the order of amino acids in a protein. Changing a single base can alter a codon, which may change one amino acid and affect how the protein folds or functions. Such mutations do not necessarily kill the organism or affect unrelated genes.

Question 12Science

Two parents with brown eyes have a child with blue eyes. Which explanation best fits this observation?

  1. The child inherited a dominant blue-eye allele from each parent
  2. Only one parent contributed genetic material
  3. Both parents carry a recessive allele for blue eyes Correct answer.
  4. Eye color is not inherited at all

Explanation

If brown eye color is dominant and blue is recessive, a blue-eyed child must inherit a recessive allele from each parent. That means both brown-eyed parents carry one hidden recessive allele and are heterozygous. The child then receives two recessive alleles and shows the blue trait.

Question 13Science

Which force acts on a book resting on a table to balance the pull of gravity?

  1. Magnetic force from Earth
  2. Friction from the air
  3. Normal force from the table Correct answer.
  4. Tension from a string

Explanation

The table pushes upward on the book with a normal force that balances the downward pull of gravity. Because these forces are equal and opposite, the book remains at rest. Air friction and magnetism are not the primary forces holding the book up.

Question 14Science

A car travels 150 meters in 10 seconds. What is its average speed?

  1. 150 m/s
  2. 1.5 m/s
  3. 15 m/s Correct answer.
  4. 1500 m/s

Explanation

Average speed equals total distance divided by total time. Dividing 150 meters by 10 seconds gives 15 meters per second. This value describes the average rate of motion over the whole trip.

Question 15Science

A ball is dropped from a height and falls freely. Which statement describes its motion, ignoring air resistance?

  1. It accelerates downward at a constant rate Correct answer.
  2. It slows down as it falls
  3. It moves upward first, then downward
  4. It moves at a constant speed

Explanation

Gravity exerts a constant downward force on a falling object near Earth's surface, producing a constant downward acceleration of about 9.8 m/s². Because speed increases steadily, the ball does not move at constant speed. Air resistance is ignored, so the acceleration stays constant.

Question 16Science

Which form of energy is stored in a stretched rubber band?

  1. Thermal energy
  2. Elastic potential energy Correct answer.
  3. Sound energy
  4. Nuclear energy

Explanation

When a rubber band is stretched, work is done to change its shape, and that energy is stored as elastic potential energy. Releasing the band converts this stored energy into kinetic energy. Thermal, sound, and nuclear energy describe other, unrelated forms.

Question 17Science

A student builds a series circuit with two identical bulbs and one battery. If one bulb is removed, what happens?

  1. The battery stops providing voltage
  2. The other bulb stays equally bright
  3. The other bulb becomes brighter
  4. Both bulbs go out because the circuit is broken Correct answer.

Explanation

In a series circuit, there is only one path for current. Removing one bulb breaks that path, so current cannot flow and both bulbs go dark. The battery still provides voltage, but no complete circuit exists.

Question 18Science

Which property of a material makes it a good electrical conductor?

  1. It blocks magnetic fields
  2. It has very high resistance
  3. Electrons can move freely through it Correct answer.
  4. It contains no charged particles

Explanation

Conductors such as copper have loosely bound electrons that can move easily when a voltage is applied. This free movement of charge carries current through the material. High resistance and lack of charged particles would instead oppose current.

Question 19Science

Light travels from air into water. What happens to its speed and direction?

  1. It stops completely at the surface
  2. It speeds up and bends away from the normal
  3. It slows down and bends toward the normal Correct answer.
  4. It keeps the same speed and direction

Explanation

Light travels more slowly in water than in air because water is optically denser. When it enters at an angle, the change in speed causes refraction, bending the ray toward the normal. This bending explains why objects look shifted underwater.

Question 20Science

Which statement about sound waves is correct?

  1. They are transverse waves in air
  2. They require a medium to travel through Correct answer.
  3. They travel faster than light in air
  4. They can travel through a vacuum

Explanation

Sound is a mechanical wave produced by vibrating particles, so it needs a medium such as air, water, or a solid to travel. In a vacuum there are no particles to carry the vibrations. In air, sound travels as a longitudinal wave and much slower than light.

Question 21Science

Earth experiences seasons mainly because of which factor?

  1. The rotation of Earth on its axis each day
  2. The tilt of Earth's axis as it orbits the Sun Correct answer.
  3. Changes in the distance between Earth and the Sun
  4. Variations in the Sun's energy output

Explanation

Earth's axis is tilted about 23.5 degrees, so different hemispheres receive more direct sunlight at different points in the orbit. This tilt, not distance from the Sun, causes the seasons. Daily rotation causes day and night rather than seasons.

Question 22Science

Which layer of Earth is mostly liquid and responsible for generating the magnetic field through its motion?

  1. Mantle
  2. Crust
  3. Inner core
  4. Outer core Correct answer.

Explanation

The outer core is a layer of liquid metal, mainly iron and nickel, that circulates and generates Earth's magnetic field. The inner core is solid, the crust is rocky and thin, and the mantle is mostly solid rock that flows very slowly. Only the outer core is liquid metal in motion.

Question 23Science

A rock layer contains fossils of a marine shellfish high on a mountain. Which conclusion is best supported?

  1. The shellfish could fly
  2. The fossils were blown there by wind
  3. The mountain formed from volcanic ash only
  4. The area was once covered by water Correct answer.

Explanation

Marine fossils in rock indicate that the rock formed in a watery environment where those organisms lived. Later geological processes uplifted the rock to form the mountain. This evidence supports the idea that the area was once underwater.

Question 24Science

A population of insects develops resistance to a pesticide over many generations. Which mechanism best explains this?

  1. Random chance alone, with no inheritance
  2. Individual insects choosing to become resistant
  3. The pesticide teaching insects how to survive
  4. Natural selection acting on inherited variation Correct answer.

Explanation

Some insects carry inherited traits that make them less affected by the pesticide. These individuals survive and reproduce, passing the favorable traits to offspring, so resistance becomes more common over generations. This is natural selection acting on existing variation.

Question 25Science

In a controlled experiment testing how fertilizer affects plant growth, which is the independent variable?

  1. The amount of water given
  2. The amount of fertilizer given Correct answer.
  3. The height of the plants
  4. The type of soil used

Explanation

The independent variable is the factor the experimenter deliberately changes, which here is the amount of fertilizer. Plant height is the dependent variable measured as the outcome. Soil type and water amount should be kept constant as controlled variables.

Question 26Science

Which organelle is the main site of aerobic respiration and ATP production in a eukaryotic cell?

  1. Mitochondrion Correct answer.
  2. Ribosome
  3. Lysosome
  4. Golgi apparatus

Explanation

Aerobic respiration releases energy from glucose, and most of the ATP produced in eukaryotic cells is made inside the mitochondrion. Ribosomes build proteins, the Golgi packages them, and lysosomes digest materials, so none of those carry out the main energy-releasing reactions.

Question 27Science

A plant cell is placed in a strong salt solution. Which change is most likely to occur?

  1. The cell becomes flaccid as water leaves it Correct answer.
  2. The cell bursts as water enters it
  3. The cell produces more chlorophyll to adapt
  4. The cell wall dissolves in the salt solution

Explanation

The salt solution has a lower water concentration than the cell contents, so water moves out of the cell by osmosis. As the vacuole loses water the cell loses turgor pressure and becomes flaccid, and the rigid wall prevents it from collapsing completely.

Question 28Science

Which process produces genetically varied offspring from two parents?

  1. Binary fission
  2. Sexual reproduction Correct answer.
  3. Vegetative propagation
  4. Cloning by cuttings

Explanation

Sexual reproduction combines gametes from two parents, and the random mixing of alleles during meiosis and fertilisation creates new gene combinations. The other processes listed produce offspring that are genetically identical or nearly identical to a single parent.

Question 29Science

A pure-breeding tall pea plant is crossed with a pure-breeding short pea plant and all the offspring are tall. Which conclusion is best supported?

  1. The tall allele is dominant over the short allele Correct answer.
  2. Height in peas is controlled only by the environment
  3. The short allele is dominant over the tall allele
  4. The offspring have mutated to become tall

Explanation

When two pure-breeding parents give offspring that all show one trait, the allele for that trait must be dominant and mask the recessive allele. The short allele is still present in the offspring but is not expressed in their appearance.

Question 30Science

Which statement correctly describes the role of DNA in protein synthesis?

  1. DNA directly joins amino acids together into a protein chain
  2. DNA is the enzyme that copies itself into protein molecules
  3. DNA is the molecule that carries amino acids to the ribosome
  4. DNA provides the base sequence that is transcribed into messenger RNA Correct answer.

Explanation

The base sequence of a gene is copied into messenger RNA during transcription, and the ribosome then reads that sequence to assemble amino acids in the correct order. DNA itself does not leave the nucleus or carry amino acids.

Question 31Science

A student pushes a box with a force of 30 N to the right while friction acts on it with 10 N to the left. What is the net force on the box?

  1. 30 N to the right
  2. 40 N to the right
  3. 10 N to the right
  4. 20 N to the right Correct answer.

Explanation

Forces acting in opposite directions are subtracted, so the net force is 30 N minus 10 N, which equals 20 N. The net force points in the direction of the larger force, which is to the right.

Question 32Science

A cyclist accelerates uniformly from rest to 12 m/s in 6 seconds. What is the acceleration?

  1. 72 m/s²
  2. 0.5 m/s²
  3. 2 m/s² Correct answer.
  4. 18 m/s²

Explanation

Acceleration equals the change in velocity divided by the time taken, so 12 m/s divided by 6 s gives 2 m/s². Starting from rest means the change in velocity is simply the final velocity of 12 m/s.

Question 33Science

A student pulls a 10 kg box across a floor using a horizontal force of 50 N while friction is 20 N. What is the acceleration of the box?

  1. 7 m/s²
  2. 5 m/s²
  3. 3 m/s² Correct answer.
  4. 2 m/s²

Explanation

The net force is 50 N minus 20 N, which equals 30 N. Using Newton's second law, a = F/m = 30 N / 10 kg = 3 m/s².

Question 34Science

Which change would increase the kinetic energy of a moving object the most?

  1. Halving its speed
  2. Doubling its mass
  3. Doubling its speed Correct answer.
  4. Halving its mass

Explanation

Kinetic energy depends on the square of speed, so doubling speed multiplies the energy by four. Doubling mass only doubles the energy, and halving either quantity reduces it.

Question 35Science

A 60 W lamp is switched on for 5 minutes. How much energy does it transfer?

  1. 3 600 J
  2. 300 J
  3. 12 J
  4. 18 000 J Correct answer.

Explanation

Energy equals power multiplied by time, and 5 minutes is 300 seconds. Multiplying 60 W by 300 s gives 18 000 J.

Question 36Science

Why is a metal spoon in a hot drink soon hot to touch at the handle?

  1. Metals trap hot air inside their structure
  2. Hot water flows up the spoon by convection
  3. Metals conduct heat well through free electrons Correct answer.
  4. Metals are good insulators that hold heat

Explanation

Heat travels through a solid metal by conduction, and metals are efficient conductors because free electrons transfer energy quickly between particles. The handle warms because energy moves along the metal from the hot end.

Question 37Science

A ray of light strikes a plane mirror at an angle of 30° to the mirror surface. What is the angle of reflection, measured from the normal?

  1. 60° Correct answer.
  2. 120°
  3. 30°
  4. 90°

Explanation

The angle of incidence is measured from the normal, which is 90° minus 30°, giving 60°. The law of reflection states that the angle of reflection equals the angle of incidence.

Question 38Science

Which statement about the pitch of a sound is correct?

  1. Higher pitch corresponds to a longer wavelength
  2. Higher pitch corresponds to a higher frequency Correct answer.
  3. Higher pitch corresponds to a larger amplitude
  4. Higher pitch corresponds to a slower wave speed in air

Explanation

Pitch is how high or low a sound seems, and it is determined by frequency: more vibrations per second give a higher pitch. Amplitude controls loudness instead, and wavelength is inversely related to frequency.

Question 39Science

A spring is compressed and then released. Which energy transfer occurs as it pushes a block?

  1. Kinetic energy to thermal energy only
  2. Elastic potential energy to kinetic energy Correct answer.
  3. Gravitational potential energy to sound energy
  4. Chemical energy to electrical energy

Explanation

A compressed spring stores elastic potential energy, and as it returns to shape this is transferred to the block as kinetic energy. Some energy may also become sound and heat, but the main useful transfer is to motion.

Question 40Science

Why does the Moon show phases when viewed from Earth?

  1. The changing angle between the Sun, Moon and Earth shows different lit portions Correct answer.
  2. Earth's shadow falls on the Moon every night
  3. The Moon produces its own light that dims and brightens
  4. The Moon spins so fast that its lit side changes hourly

Explanation

Half of the Moon is always lit by the Sun, but as the Moon orbits Earth we see that lit half from different angles, producing the phases. Earth's shadow causes eclipses only occasionally, not the regular cycle of phases.

Question 41Science

Which evidence best supports the theory that Earth's tectonic plates move?

  1. Seasonal changes in day length
  2. The presence of craters on the Moon
  3. The daily rising and setting of the Sun
  4. Matching rock types and fossils on continents now far apart Correct answer.

Explanation

Similar rocks and fossils found on continents separated by oceans suggest those landmasses were once joined and have since drifted apart. This is one of the key lines of evidence for plate movement.

Question 42Science

Which type of rock forms when molten material cools and solidifies?

  1. Sedimentary rock
  2. Fossiliferous limestone
  3. Igneous rock Correct answer.
  4. Metamorphic rock

Explanation

Igneous rocks crystallise from magma or lava as it cools. Sedimentary rocks form from compacted deposits, and metamorphic rocks form when existing rocks are changed by heat and pressure.

Question 43Science

Two populations of the same bird species live on opposite sides of a wide river and cannot interbreed. Over a long time, what is most likely to happen?

  1. They will merge back into one breeding population
  2. They will stop responding to natural selection
  3. They will become genetically identical
  4. They may evolve into separate species Correct answer.

Explanation

When populations are separated and cannot exchange genes, mutations and selection act independently in each group. Over many generations these differences can become so great that the populations can no longer interbreed, forming separate species.

Question 44Science

In a garden, aphids feed on rose plants and ladybirds eat the aphids. Which term describes the ladybirds?

  1. Decomposers
  2. Primary consumers
  3. Producers
  4. Secondary consumers Correct answer.

Explanation

Aphids eat the rose plants and are therefore primary consumers. Ladybirds eat the aphids, so they occupy the next level of the food chain and are secondary consumers.

Question 45Science

A population of rabbits increases rapidly in a meadow with limited food. What is most likely to happen next?

  1. The population will keep growing at the same rate indefinitely
  2. The population will fall as competition for food increases Correct answer.
  3. The rabbits will switch to making their own food
  4. The meadow will produce unlimited extra grass

Explanation

Food supply is a limiting factor, so as the population grows competition for resources intensifies. Death rates rise and birth rates fall until the population levels off or drops.

Question 46Science

Which human activity contributes most directly to the greenhouse effect by adding carbon dioxide to the atmosphere?

  1. Building dams for hydropower
  2. Planting trees in a forest
  3. Burning fossil fuels for electricity Correct answer.
  4. Recycling aluminium cans

Explanation

Burning coal, oil and gas releases carbon dioxide that was stored underground, increasing the concentration of greenhouse gases. This traps more heat in the atmosphere and strengthens the greenhouse effect.

Question 47Science

A substance has a fixed volume but takes the shape of its container. In which state of matter is it?

  1. Gas
  2. Plasma
  3. Solid
  4. Liquid Correct answer.

Explanation

Particles in a liquid are close together, giving a fixed volume, but they can slide past one another, so the liquid flows to fit its container. Solids keep their own shape, and gases spread to fill any space.

Question 48Science

A student dissolves 20 g of salt in 80 g of water. What is the mass of the resulting solution?

  1. 80 g
  2. 100 g Correct answer.
  3. 60 g
  4. 20 g

Explanation

Mass is conserved when a solute dissolves, so the total mass is the mass of the salt plus the mass of the water. Adding 20 g and 80 g gives 100 g.

Question 49Science

Which observation shows that a chemical change has taken place?

  1. Ice melts into liquid water
  2. Sugar dissolves in warm water
  3. A metal wire is bent into a loop
  4. A new gas is produced with a different smell Correct answer.

Explanation

A chemical change produces new substances with different properties, such as a new gas, a colour change or a precipitate. Melting, dissolving and bending change only the form or arrangement of the same substance.

Question 50Science

A student wants to test whether the amount of light affects how fast pondweed produces bubbles. Which variable should be changed between trials?

  1. The distance of the lamp from the pondweed Correct answer.
  2. The mass of pondweed used
  3. The temperature of the water
  4. The volume of water in the beaker

Explanation

The independent variable is the factor deliberately changed, which here is the light intensity set by the lamp distance. All other conditions must be kept constant so that any change in bubble rate can be attributed to light.