Free GED Science Physical Science Practice Test — Questions and Answers

Question 1: What is the SI unit of force?

Kilogram
Joule
Newton (Correct answer)
Watt

Correct answer: Newton

The SI unit of force is the Newton (N), named after Isaac Newton. 1 Newton = 1 kg·m/s².

Question 2: Which of Newton's Laws states that an object in motion stays in motion unless acted upon by an external force?

Newton's First Law (Inertia) (Correct answer)
Newton's Second Law (F = ma)
Newton's Third Law (Action-Reaction)
Newton's Law of Gravitation

Correct answer: Newton's First Law (Inertia)

Newton's First Law of Motion states that an object at rest stays at rest, and an object in motion stays in motion, unless acted upon by a net external force — this is the law of inertia.

Question 3: What happens to the temperature of water when it boils at 100°C and becomes steam?

The temperature increases rapidly
The temperature decreases
The temperature stays constant during the phase change (Correct answer)
The temperature fluctuates randomly

Correct answer: The temperature stays constant during the phase change

During a phase change (like boiling), energy is used to break intermolecular bonds rather than increase temperature. The temperature remains constant at 100°C until all the water has turned to steam.

Question 4: What is the formula for calculating work?

W = m × v
W = F × d (Correct answer)
W = P × t
W = m × a

Correct answer: W = F × d

Work = Force × distance (W = Fd). Work is measured in Joules (J).

Question 5: Which of the following is a chemical change (not a physical change)?

Ice melting into water
Paper being cut into pieces
Wood burning (Correct answer)
Salt dissolving in water

Correct answer: Wood burning

Burning wood is a chemical change — it produces new substances (ash, CO₂, water vapor) through a chemical reaction. The other options are physical changes.

Question 6: What is the atomic number of an element?

The number of neutrons in the nucleus
The total number of protons and neutrons
The number of protons in the nucleus (Correct answer)
The mass of the atom

Correct answer: The number of protons in the nucleus

The atomic number is the number of protons in an atom's nucleus. It uniquely identifies the element and determines its position on the periodic table.

Question 7: Which type of wave requires a medium to travel?

Radio waves
Light waves
Sound waves (Correct answer)
X-rays

Correct answer: Sound waves

Sound waves are mechanical waves that require a medium (solid, liquid, or gas) to travel through. Electromagnetic waves (light, radio, X-rays) can travel through a vacuum.

Question 8: Ohm's Law states that voltage (V) equals:

Current × Resistance (V = IR) (Correct answer)
Power × Time (V = Pt)
Current / Resistance (V = I/R)
Resistance / Current (V = R/I)

Correct answer: Current × Resistance (V = IR)

Ohm's Law: V = IR, where V is voltage (volts), I is current (amperes), and R is resistance (ohms).

Question 9: What is the law of conservation of energy?

Energy can be created from nothing under certain conditions
Energy cannot be created or destroyed, only converted from one form to another (Correct answer)
Energy decreases over time due to friction
Energy only exists in kinetic and potential forms

Correct answer: Energy cannot be created or destroyed, only converted from one form to another

The law of conservation of energy states that energy cannot be created or destroyed — it can only be transformed from one form (kinetic, potential, thermal, etc.) to another.

Question 10: An atom has 17 protons, 18 neutrons, and 17 electrons. What is its atomic mass?

17
18
34
35 (Correct answer)

Correct answer: 35

Atomic mass = protons + neutrons = 17 + 18 = 35. (This is the element chlorine, Cl-35.)

Question 11: Which of the following best describes a conductor?

A material that blocks the flow of electric current
A material that allows electric current to flow easily (Correct answer)
A material that converts electrical energy to heat
A material that stores electrical charge

Correct answer: A material that allows electric current to flow easily

A conductor is a material (like copper or aluminum) that allows electric charges to move freely, enabling the flow of electric current.

Question 12: What is the difference between a physical change and a chemical change?

Physical changes always involve heat; chemical changes do not
Physical changes alter the form of a substance without changing its chemical composition; chemical changes produce new substances (Correct answer)
Chemical changes are reversible; physical changes are not
There is no meaningful difference

Correct answer: Physical changes alter the form of a substance without changing its chemical composition; chemical changes produce new substances

Physical changes (melting, freezing, cutting) change the form or appearance without altering chemical composition. Chemical changes (burning, rusting, cooking) produce new substances with different chemical properties.

Question 13: A 5 kg object is accelerated at 3 m/s². What is the net force acting on it?

8 N
10 N
15 N (Correct answer)
20 N

Correct answer: 15 N

F = ma = 5 kg × 3 m/s² = 15 N.

Question 14: Which of the following is an example of potential energy?

A car moving at 60 mph
A book resting on a high shelf (Correct answer)
A spinning top
A running river

Correct answer: A book resting on a high shelf

Potential energy is stored energy based on position or condition. A book on a high shelf has gravitational potential energy due to its position above the ground.

Question 15: What type of bond forms when one atom completely transfers an electron to another atom?

Covalent bond
Metallic bond
Ionic bond (Correct answer)
Hydrogen bond

Correct answer: Ionic bond

An ionic bond forms when one atom completely transfers one or more electrons to another, creating oppositely charged ions that attract each other.

Question 16: The Periodic Table organizes elements primarily by:

Alphabetical order of element names
Increasing atomic number (Correct answer)
Mass and color
Date of discovery

Correct answer: Increasing atomic number

The modern Periodic Table arranges elements in order of increasing atomic number (number of protons), with rows (periods) and columns (groups) reflecting chemical and physical properties.

Question 17: Which of the following describes the speed of light?

300 km/s
3,000 km/s
300,000 km/s (Correct answer)
3,000,000 km/s

Correct answer: 300,000 km/s

The speed of light in a vacuum is approximately 300,000 km/s (or 3 × 10⁸ m/s).

Question 18: What is the difference between an acid and a base?

Acids have a pH above 7; bases have a pH below 7
Acids donate protons (H⁺ ions); bases accept protons (Correct answer)
Acids are always solids; bases are always liquids
Acids are natural; bases are man-made

Correct answer: Acids donate protons (H⁺ ions); bases accept protons

According to the Brønsted-Lowry definition, acids donate hydrogen ions (H⁺) and bases accept them. Acids have pH below 7; bases have pH above 7.

Question 19: In a chemical equation, what does the Law of Conservation of Mass require?

Products must weigh more than reactants
The number of atoms on both sides of the equation must be equal (Correct answer)
Reactions always release energy
Only organic compounds can react

Correct answer: The number of atoms on both sides of the equation must be equal

The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. The total number of atoms of each element must be the same on both sides of the balanced equation.

Question 20: Which subatomic particle has a negative charge?

Proton
Neutron
Electron (Correct answer)
Quark

Correct answer: Electron

Electrons have a negative charge (-1). Protons have a positive charge (+1). Neutrons have no charge (0).

Question 21: What happens when light passes from air into glass?

It speeds up and bends away from the normal
It slows down and bends toward the normal (refraction) (Correct answer)
It stops completely
Its frequency increases

Correct answer: It slows down and bends toward the normal (refraction)

When light passes from a less dense medium (air) to a more dense medium (glass), it slows down and bends toward the normal — this is refraction.

Question 22: On the pH scale, a solution with pH 2 is best described as:

Strongly basic
Slightly acidic
Strongly acidic (Correct answer)
Neutral

Correct answer: Strongly acidic

The pH scale runs from 0 to 14. pH 7 is neutral. Values below 7 are acidic; values above 7 are basic. pH 2 is strongly acidic.

Question 23: Which of the following is an example of kinetic energy?

A stretched rubber band
A ball rolling down a hill (Correct answer)
A boulder balanced at the top of a cliff
Chemical energy stored in food

Correct answer: A ball rolling down a hill

Kinetic energy is the energy of motion. A ball rolling down a hill is in motion, so it possesses kinetic energy.

Question 24: What does the term 'isotope' mean?

Two different elements with the same number of electrons
Atoms of the same element with different numbers of neutrons (Correct answer)
Atoms with the same atomic mass but different atomic numbers
A radioactive form of any molecule

Correct answer: Atoms of the same element with different numbers of neutrons

Isotopes are atoms of the same element (same number of protons) that differ in the number of neutrons. Carbon-12 and Carbon-14 are isotopes.

Question 25: A 100W light bulb is on for 5 hours. How much energy does it use? (Energy = Power × Time)

20 Wh
100 Wh
500 Wh (Correct answer)
1,000 Wh

Correct answer: 500 Wh

Energy = 100 W × 5 hours = 500 Watt-hours (Wh).

Question 26: Which of the following is NOT a type of electromagnetic radiation?

X-rays
Gamma rays
Sound waves (Correct answer)
Ultraviolet light

Correct answer: Sound waves

Sound waves are mechanical waves requiring a medium — they are NOT electromagnetic. X-rays, gamma rays, and ultraviolet light are all forms of electromagnetic radiation.

Question 27: The noble gases (Group 18) are chemically stable because:

They have very high atomic masses
Their outermost electron shells are completely filled (Correct answer)
They are toxic and cannot react
They only exist at high temperatures

Correct answer: Their outermost electron shells are completely filled

Noble gases have complete outer electron shells (usually 8 electrons — the 'octet'), making them very stable and unreactive.

Question 28: What is the difference between speed and velocity?

They are the same thing
Speed is a scalar (magnitude only); velocity includes both magnitude and direction (Correct answer)
Velocity is always greater than speed
Speed includes direction; velocity does not

Correct answer: Speed is a scalar (magnitude only); velocity includes both magnitude and direction

Speed is a scalar quantity with only magnitude (e.g., 60 mph). Velocity is a vector quantity that includes both magnitude and direction (e.g., 60 mph north).

Question 29: Which type of radiation has the highest penetrating power?

Alpha particles
Beta particles
Gamma rays (Correct answer)
Infrared waves

Correct answer: Gamma rays

Gamma rays are high-energy electromagnetic radiation with the greatest penetrating power. Alpha particles can be stopped by paper; beta particles by thin metal; gamma rays require thick lead or concrete.

Question 30: What is a catalyst?

A product formed during a chemical reaction
A substance that is consumed in a chemical reaction
A substance that speeds up a chemical reaction without being consumed (Correct answer)
A substance that only slows chemical reactions

Correct answer: A substance that speeds up a chemical reaction without being consumed

A catalyst increases the rate of a chemical reaction by lowering the activation energy required, without being consumed or permanently changed in the process.

Question 31: An object is dropped from a height. Just before it hits the ground, which is true about its energy?

All energy is potential
All energy is kinetic (Correct answer)
Energy is evenly split between kinetic and potential
All energy is thermal

Correct answer: All energy is kinetic

As an object falls, potential energy converts to kinetic energy. Just before hitting the ground (assuming no air resistance), essentially all the energy has been converted to kinetic energy.

Question 32: What is the formula for density?

Density = Volume / Mass
Density = Mass × Volume
Density = Mass / Volume (Correct answer)
Density = Force / Area

Correct answer: Density = Mass / Volume

Density = Mass / Volume (D = m/V). It is typically expressed in g/cm³ or kg/m³.

Question 33: Which element makes up the majority of the Sun?

Helium
Oxygen
Hydrogen (Correct answer)
Carbon

Correct answer: Hydrogen

The Sun is approximately 73% hydrogen (by mass). Nuclear fusion of hydrogen into helium in the core produces the Sun's energy.

Question 34: When two waves combine and their crests align, the result is:

Destructive interference — the waves cancel out
Constructive interference — a larger wave forms (Correct answer)
Diffraction — the waves spread out
Reflection — the waves bounce back

Correct answer: Constructive interference — a larger wave forms

When two waves align so their crests (or troughs) coincide, constructive interference occurs and the resulting amplitude is larger than either individual wave.

Question 35: What is the primary source of energy for most ecosystems on Earth?

Geothermal energy from Earth's core
Chemical energy from rocks
Solar energy from the Sun (Correct answer)
Nuclear energy from radioactive decay

Correct answer: Solar energy from the Sun

Solar energy is the primary energy source for most ecosystems. Plants and other photosynthetic organisms capture sunlight to produce food, forming the base of food chains.

Free GED Science Physical Science Practice Test

What is the SI unit of force?