Practice Exam – 300 MCQ & Constructed-
Response Guide with Detailed
Rationales (Version 2)
Question 1
A fourth-grade teacher is planning a unit on energy. She wants to demonstrate that
energy can be transferred from one object to another. She places a metal spoon in a
cup of hot water. After five minutes, the handle of the spoon feels warm to the touch.
Which of the following best explains why the handle of the spoon became warm?
A) Convection currents carried heat through the water to the spoon handle
B) Radiation from the hot water traveled up the spoon
C) Conduction transferred thermal energy through the metal spoon
D) The spoon generated its own heat through friction with the water
[CORRECT] C
Rationale: Conduction is the transfer of thermal energy through direct contact between
particles in a material. Metals are good conductors of heat because their free electrons
can transfer kinetic energy rapidly from the hot end (submerged in water) to the cooler
end (the handle). Convection (A) involves fluid movement and wouldn't explain heat
traveling through solid metal. Radiation (B) involves electromagnetic waves, not heat
traveling through a solid. The spoon does not generate its own heat (D); it simply
transfers existing thermal energy from the water.
Question 2
A science teacher is demonstrating the properties of matter to a fifth-grade class.
She fills two identical balloons: one with air and one with water. Both balloons are
the same size and volume. She places both balloons on a balance scale. The balloon
filled with water is significantly heavier than the balloon filled with air. This
demonstration best illustrates which of the following concepts?
A) Water has greater mass per unit volume than air
B) Air is weightless and has no mass
C) The balloon filled with air contains fewer molecules
D) Water expands to fill its container more than air does
[CORRECT] A
,Rationale: The demonstration illustrates density—the mass per unit volume of a
substance. Water has a much higher density than air, meaning it has more mass in the
same volume. Air does have mass (B is incorrect); the air balloon would weigh
something, just much less than the water balloon. Both balloons contain approximately
the same number of molecules (C is oversimplified and incorrect—different gases have
different molecular weights). Water does not expand to fill its container more than air
(D); in fact, liquids are relatively incompressible compared to gases.
Figure 1: Particle Arrangement in States of Matter
text
SOLID LIQUID GAS
● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ● ●
● ● ● ● ● ● ● ● ●
Fixed shape, Fixed volume, No fixed shape
fixed volume variable shape or volume
Particles vibrate Particles slide Particles move
in place past each other freely
Attraction: strong Attraction: moderate Attraction: weak
Question 3
A third-grade teacher is conducting a sink-or-float investigation with her students.
She provides objects of various materials and asks students to predict whether each
will sink or float. One student observes that a large wooden block sinks while a small
plastic bead floats. Which of the following concepts would best help the student
understand this observation?
A) The wooden block has more mass than the plastic bead
B) Density is a property of the material, not the size of the object
C) Wood is always heavier than plastic regardless of size
D) The plastic bead has less volume than the wooden block
[CORRECT] B
, Rationale: Density is an intensive property—it depends on the material itself, not the
amount of material. A small piece of a dense material sinks; a large piece of a less
dense material floats. The wooden block sinks because its density is greater than
water's density, while the plastic bead floats because its density is less than water's
density, regardless of their sizes. While the wooden block may have more mass (A), that
doesn't explain why it sinks—a large ship made of steel (dense) can float if shaped to
displace enough water. Wood is not always heavier than plastic (C). The plastic bead
has less volume (D), but volume alone doesn't determine sinking/floating.
Question 4
A fifth-grade teacher is teaching about the properties of light. She shines a flashlight
through a glass prism and observes a rainbow of colors projected onto the wall.
Which of the following best explains why the prism separates white light into
different colors?
A) Different colors of light have different wavelengths and bend at different angles
B) The prism absorbs certain colors and transmits others
C) White light is created by combining all colors in the prism
D) The prism reflects different colors at different angles
[CORRECT] A
Rationale: White light is composed of different colors of light with different
wavelengths. When white light enters a prism (a transparent medium), each color
bends (refracts) by a different amount due to dispersion—shorter wavelengths
(violet/blue) bend more than longer wavelengths (red). This separation of colors is
called dispersion. The prism does not absorb colors selectively (B) in this demonstration;
it refracts all colors. White light is not created in the prism (C); it is separated into its
component colors. While reflection occurs at the surfaces, the separation happens due
to refraction, not differential reflection (D).
Question 5
A teacher wants to demonstrate Newton's First Law of Motion to her fourth-grade
class. She places a small toy car on a flat table and gives it a gentle push. The car
moves across the table and gradually slows down and stops. Which of the following
best explains why the car eventually stops?