MDCAT Chemistry chapter 4: Chemistry · Liquids MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
45 exam-style questions on Chemistry · Liquids, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Water is boiling steadily in an open pan at 1 atm. If the flame is turned up, the temperature of the boiling water
A
rises steadily
B
stays at 100 °C
C
falls slightly
D
rises to a new fixed value above 100 °C
Show answer
Answer: B. Water boils when its vapour pressure equals the external pressure, 760 torr at 100 °C. Extra heat only supplies the heat of vaporisation faster, so the water boils away faster while its temperature stays at 100 °C.
2. Glycerol, C3H5(OH)3, is far more viscous than ethanol, C2H5OH. The main reason is that
A
it has no polar bonds, so only London forces act
B
its molecules are held by ionic bonds
C
it has a lower molar mass than ethanol
D
its three OH groups form more hydrogen bonds
Show answer
Answer: D. Each glycerol molecule has three O–H groups, so it forms an extensive network of hydrogen bonds that resists flow. Ethanol has only one O–H group per molecule.
3. Which order of hydrogen-bond strength is correct?
A
N–H···N > O–H···O > F–H···F
B
O–H···O > F–H···F > N–H···N
C
F–H···F > O–H···O > N–H···N
D
O–H···O > N–H···N > F–H···F
Show answer
Answer: C. A hydrogen bond is stronger when the atom bonded to hydrogen is more electronegative, because the H atom then carries a larger δ+ charge. Electronegativity falls in the order F (4.0) > O (3.5) > N (3.0), so F–H···F bonds are the strongest and N–H···N the weakest.
4. At 1 atm, four liquids boil at these temperatures: diethyl ether 35 °C, ethanol 78 °C, water 100 °C and ethanoic acid 118 °C. Which has the highest vapour pressure at 25 °C?
A
diethyl ether
B
ethanol
C
water
D
ethanoic acid
Show answer
Answer: A. The lowest boiling point means the weakest intermolecular forces, so most molecules escape at a given temperature. Diethyl ether's vapour pressure reaches 760 torr at only 35 °C, so it is the highest of the four at 25 °C.
5. The boiling points of methanoic, ethanoic and propanoic acids are 101 °C, 118 °C and 141 °C. The steady rise along the series is due mainly to
A
stronger London forces as the carbon chain grows
B
more hydrogen bonds per molecule as the chain grows
C
greater acid strength as the carbon chain grows
D
more complete ionisation as the chain grows
Show answer
Answer: A. Each acid has one –COOH group, so its hydrogen bonding is about the same; each extra CH2 adds electrons and surface area, increasing the London dispersion forces. Acid strength actually falls slightly from methanoic to propanoic acid.
6. Which property do liquids share with gases but not with solids?
A
they flow and have no fixed shape
B
they have a fixed volume
C
they are easily compressed
D
their particles vibrate about fixed positions
Show answer
Answer: A. In liquids and gases the particles can slide past one another, so both flow and take the shape of their container. A liquid has a fixed volume and is hardly compressible, unlike a gas, and vibration about fixed positions describes a solid.
7. The only intermolecular forces present between molecules of liquid bromine, Br2, are
A
dipole–dipole forces
B
hydrogen bonds
C
London dispersion forces
D
dipole–induced dipole forces
Show answer
Answer: C. Br2 is a non-polar molecule (two identical atoms), so it has no permanent dipole. Only London forces, from temporary dipoles in its large electron cloud, hold the liquid together.
8. Two pieces of ice pressed firmly together join into a single piece. Which attractions hold the two pieces together at the join?
A
covalent bonds between oxygen atoms of the two surfaces
B
ionic bonds between H+ and OH− ions
C
hydrogen bonds between the water molecules at the join
D
London forces only, since water molecules are non-polar
Show answer
Answer: C. Where the surfaces meet, water molecules from the two pieces come close enough to form new O–H···O hydrogen bonds, the same attractions that hold the ice crystal together, so the pieces fuse. Water is polar, and no covalent or ionic bonds are made.
9. Between the molecules of which liquid are there dipole–dipole forces but no hydrogen bonds?
A
acetone, CH3COCH3
B
carbon tetrachloride, CCl4
C
methanol, CH3OH
D
benzene, C6H6
Show answer
Answer: A. Acetone has a polar C=O bond, so its molecules have permanent dipoles, but no H atom is bonded to O, N or F, so its molecules cannot hydrogen bond to one another. CCl4 and benzene are non-polar, and methanol has an O–H group and forms hydrogen bonds.
10. A drop of ink spreads through still water far more slowly than the smell of perfume spreads through still air. Why?
A
the molecules of a liquid are not moving at all
B
ink particles have more kinetic energy than perfume molecules
C
liquid molecules are closely packed and collide constantly
D
diffusion can occur only in gases, never in liquids
Show answer
Answer: C. Liquid molecules do move and diffuse, but they are closely packed with little free space, so each one travels only a tiny distance before colliding and is held back by intermolecular forces. In a gas the molecules are far apart and move freely, so diffusion is much faster.
45, each with the answer and a short explanation, across 2 topics: Intermolecular forces, Properties of liquids. Every chapter test draws ten of them, so you can take it many times.
Is the MDCAT Chemistry chapter 4 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
