Cause and Effect Reasoning MCQs for MDCAT Practice

Science Reasoning section, Cause and Effect Reasoning chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

1. Question 1
   If magnesium burns in air, forming a white ash, what does this indicate?
   • APhysical change
   • BLoss of mass
   • CChemical reaction with oxygen (correct answer)
   • DFreezing point of magnesium
   Correct answer: C

   Burning magnesium in air forms a white ash, indicating a chemical reaction with oxygen, not just a physical change, mass loss, or freezing point.
2. Question 2
   A person inhales carbon monoxide. What makes it dangerous?
   • AIt causes immediate suffocation
   • BIt binds to hemoglobin more strongly than oxygen (correct answer)
   • CIt burns the lungs
   • DIt forms water in the blood
   Correct answer: B

   Carbon monoxide is dangerous because it hijacks oxygen's transport system by binding irreversibly to hemoglobin.
3. Question 3
   If 10 clothes are dried up together in 1 hour, in how many hours can 20 clothes be dried up together?
   • A1 hour (correct answer)
   • B2 hours
   • C3 hours
   • D4 hours
   Correct answer: A

   The drying time of clothes is determined by environmental factors, not the number of clothes dried simultaneously, as long as conditions remain constant.
4. Question 4
   A battery is connected to a resistor. What happens when resistance increases?
   • ACurrent increases
   • BVoltage decreases
   • CCurrent decreases (correct answer)
   • DBattery explodes
   Correct answer: C

   Increasing resistance in a simple circuit with a fixed voltage source leads to a decrease in current, as dictated by Ohm's Law.
5. Question 5
   The radius of the second orbit in hydrogen atom is
   • AGreater than the first orbit (correct answer)
   • BEqual to the first orbit
   • CLess than the first orbit
   • DNone of these
   Correct answer: A

   In Bohr's model of the hydrogen atom, the radius of electron orbits increases with the principal quantum number (n), meaning the second orbit is larger than the first.
6. Question 6
   The compounds BrCl and BrI melt at –66°C and 42°C, respectively.What is the best explanation for this difference in melting points?
   • AThe Br-I covalent bond is stronger than the Br−Cl covalent bond
   • BChlorine is more reactive than iodine so chlorine breaks away from bromine more readily than iodine
   • CThe forces between BrI molecules are stronger than the forces between BrCl molecules (correct answer)
   • DIodide ions are larger than chloride ions so bromide ions form stronger ionic bonds with iodide ions than with chloride ions
   Correct answer: C

   Higher melting point for BrI vs BrCl is due to stronger intermolecular forces, not bond strength or ionic character.
7. Question 7
   A pendulum clock runs slow in summer. Why?
   • AExpansion increases its length (correct answer)
   • BHeat speeds up motion
   • CWeight changes
   • DAir resistance is more
   Correct answer: A

   A pendulum clock runs slow in summer due to thermal expansion of its length, increasing the period of oscillation.
8. Question 8
   Why are safety goggles used in labs?
   • AThey correct vision
   • BThey are fashionable
   • CThey protect from splashes and fumes (correct answer)
   • DThey detect color change
   Correct answer: C

   Safety goggles are essential lab attire, acting as a physical barrier to protect eyes from hazardous chemicals and physical projectiles.

Read the full Cause and Effect Reasoning chapter notes: Cause and Effect Reasoning notes. Or browse every chapter.