Free Scientific Reasoning MCQs with Answers
334 Scientific Reasoning MCQs from Analytical and Logical Reasoning, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Scientific reasoning evaluates hypotheses through observations, variables, controls, measurements and experimental results. Questions involve identifying independent and dependent variables, recognising a fair test, interpreting tables or graphs, distinguishing evidence from opinion, and deciding whether data supports, rejects or leaves a hypothesis unresolved.
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Read the Scientific Reasoning notesFree MDCAT chapter notes with key terms334 questions · page 15 of 17
281. Why does the burning of a tire yield black smoke while burning stoves in homes rarely produce smoke?
- A. Burning tires cause parts of the tires to break off and fly off in the air, causing the appearance of black smoke
- B. Combustion of heavy fuels such as tires causes incomplete combustion which yields elemental carbon which is black
- C. The heat of the fire causes tires to melt and eventually evaporate, as a result, the vapors in the smoke appear black
- D. None of the above options are correct
Explanation: Thick, black smoke indicates heavy fuels that are not being fully consumed.
Correct answer: Combustion of heavy fuels such as tires causes incomplete combustion which yields elemental carbon which is black- A. The rapid pulling of the table cloth causes the plates and cloth to be charged. The repulsion of like charges then causes a levitation force to lift up the cutlery subtly
- B. The cloth is slippery and offers no friction hence can be slipped out
- C. The instant nature of the movement coupled with the inertia of the cutlery prevents any movement of the cutlery
- D. The cutlery is held permanently in the same position by gravitational force
Explanation: If the tablecloth is pulled slowly, friction (rubbing) between the cutlery and the tablecloth will cause the tablecloth to pull the…
Correct answer: The instant nature of the movement coupled with the inertia of the cutlery prevents any movement of the cutlery- A. None of these.
- B. The beating movement charges the carpet by friction and repels the dust off of it
- C. The beating causes a reaction force by the carpet which also applies to the dust particles, causing their expulsion
- D. The beating loosens the fibers of the carpet causing the dust trapped in them to come loose
Explanation: The inertia of the dust particles residing on the carpet resists the change in the carpet's motion.
Correct answer: The beating loosens the fibers of the carpet causing the dust trapped in them to come loose- A. They are actually falling due to gravity but their horizontal velocity is so large that they end up orbiting instead of hitting the surface
- B. The reaction force to gravity keeps them in a balanced state and prevents them from falling
- C. The gravitational force due to the Moon prevents this
- D. They have thrusters to prevent them from falling down
Explanation: In actuality, satellites are indeed "falling" due to gravity. However, their horizontal velocity is so high that they keep "falling"…
Correct answer: They are actually falling due to gravity but their horizontal velocity is so large that they end up orbiting instead of hitting the surface- A. Men do not take care of their eyes well enough
- B. Men spend more time in front of digital screens than women
- C. Color blindness is a sex-linked genetic disease
- D. Men usually aren't able to distinguish between colors due to some circuitry in their right hemisphere of the brain
Explanation: Since it's passed down on the X chromosome, red-green color blindness is more common in men.
Correct answer: Color blindness is a sex-linked genetic disease- A. Lactic acid bacteria
- B. Bacillus radicicola
- C. Lactobacillus aureus
- D. Lactobacillus Acidophillus
Explanation: Curd may contain a wide variety of bacteria like Lactobacillus acidophilus, Lactococcus lactis, Lactococcus lactis cremoris, etc.
Correct answer: Lactobacillus Acidophillus- A. The sun's rays have to pass through a larger distance in the atmosphere. Most of the blue and other shorter wavelengths are removed by scattering and red light enters our eye
- B. The Sun has sides of different colors similar to the Moon's dark and bright side. Hence, at sunset, we are facing the red side of the Sun
- C. At the time of sunset, fusion reactions of the Sun are so intense that the color of the Sun's flame changes from yellow to red
- D. Plants release red chemicals at the time of sunset which diffuses into the sky and fluoresces, giving the sky a red color
Explanation: When the Sun is setting, the light that reaches you has had to go through lots more atmosphere than when the sun is overhead, hence the…
Correct answer: The sun's rays have to pass through a larger distance in the atmosphere. Most of the blue and other shorter wavelengths are removed by scattering and red light enters our eye- A. 320 billion kg
- B. 7 billion kg
- C. 320 million kg
- D. 2 billion kg
Explanation: There are approximately 8 billion people on Earth. If we approximate the average weight to be 40 kg, we come to the approximate value of…
Correct answer: 320 billion kg- A. Meat from mountainous animals is stronger than animals on the ground level
- B. The boiling point of water is lower at higher altitudes.
- C. Pathogens and pollutants in urban cities located on ground levels make already cause the meat to rot a bit before we begin to cook it
- D. None of the above
Explanation: Because water boils at a lower temperature at higher elevations, foods that are prepared by boiling or simmering will cook at a lower…
Correct answer: The boiling point of water is lower at higher altitudes.- A. To prevent someone from bumping into them and hurting themselves
- B. So that the cool wind directly hits the person's face, causing them instant relief
- C. It's just a standard, you can place the units anywhere you like
- D. To set up convection currents to cool the room since the cool air is denser and settles down
Explanation: Warmer air at the bottom is displaced and due to it being less dense, it rises.
Correct answer: To set up convection currents to cool the room since the cool air is denser and settles down- A. In water bodies, only the top layer freezes in winters, allowing aquatic life to survive
- B. They have cold-shock proteins which allow them to survive via hibernating while they are frozen
- C. The aquatic life migrates out before the water bodies freeze
- D. They do not survive but they lay their eggs before winter starts. The off-spring then recreate the population from scratch
Explanation: Only the top layer of a lake or river freezes, underneath the frozen upper layer the water remains in its liquid form and does not freeze.
Correct answer: In water bodies, only the top layer freezes in winters, allowing aquatic life to survive- A. The greenhouse effect leads to global warming and the solution to global warming is to go green i.e. to plant more trees. Hence it is called the greenhouse effect
- B. The heating effect caused by greenhouse gases is similar to that caused by the glass in a greenhouse
- C. The scientist who invented the term loved the color green
- D. None of the above options are correct
Explanation: The process is called the greenhouse effect because the exchange of incoming and outgoing radiation that warms the planet works in a…
Correct answer: The heating effect caused by greenhouse gases is similar to that caused by the glass in a greenhouse- A. The impact from any object falling out of the train can be extremely injurious due to the velocity of the train
- B. The fast movement in front of your eyes will make you feel dizzy and cause you to faint
- C. The fast-moving train creates a strong air pressure which can cause you to fall and hurt yourself
- D. It's just a disciplinary measure, there is no harm in standing close to a fast-moving train
Explanation: When a fast-moving train passes on a rail, the velocity of the air stream in between the rail and the by-stander standing near the rail is…
Correct answer: The fast-moving train creates a strong air pressure which can cause you to fall and hurt yourself- A. The slippery nature of the soap causes the germs to slip off
- B. The soap traps germs and dirt and is washed off with them
- C. The soap produces free radicles which destroy the germs on our hands
- D. The soap disintegrates grease on the skin due to its non-polar tail
Explanation: The following picture shows the explanation to this question:
Correct answer: The soap disintegrates grease on the skin due to its non-polar tail- A. III>I>IV>II
- B. II>III>IV>I
- C. I>III>IV>II
- D. I>II>III>IV
Explanation: To obtain dry iron, we first hold a magnet above the mixture. We then mix the remaining salt and sand into water.
Correct answer: III>I>IV>II- A. There is a microphone attached near to the strings and a speaker connected to it amplifies the volume
- B. Resonance in the soundhole allows for amplification of the voice
- C. Special kinds of strings are used which enable a louder sound to be produced
- D. The tension in the strings is especially higher so it produces a louder sound
Explanation: Sound-hole, a hollow chamber, is an essential component of stringed musical instruments, and enhances the sound radiation in the lower…
Correct answer: Resonance in the soundhole allows for amplification of the voice- A. Red blood cells
- B. Ciliated cells of the trachea
- C. E.coli from the stomach
- D. Fungi mycellium
Explanation: E.coli being a prokaryote lacks nucleus, has a cell wall and may have a flagella
Correct answer: E.coli from the stomach- A. All of the above
- B. Brain death/damage from low oxygen supply
- C. Malnutrition
- D. Lower birth weight
Explanation: The umbilical cord provides oxygen and nutrients to the fetus. A lack of its functionality would lead to all of the above mentioned symptoms
Correct answer: All of the above- A. appears not to be a link
- B. appears to be a link
- C. cannot make a reasonable guess
- D. The size causes the tail color to change
Explanation: With very few exceptions, fat mice usually have black tails and small mice had white tails.
Correct answer: appears to be a link- A. It provides air resistance to objects entering Earth, hence burning and destroying meteors before they can land on the surface
- B. Ozone disintegrates into oxygen which is needed for cellular respiration
- C. The ozone layer absorbs harmful radiation which may cause skin cancer if exposed to
- D. Ozone captures free radicals such as chlorine which may damage human tissues if inhaled
Explanation: The stratospheric ozone layer is Earth's "sunscreen" - protecting living things from too much ultraviolet radiation from the sun, and…
Correct answer: The ozone layer absorbs harmful radiation which may cause skin cancer if exposed to