ASVAB General Science: Physics and Chemistry Concepts — Questions and Answers
Question 1: What is Newton's First Law of Motion?
- Force equals mass times acceleration
- An object at rest stays at rest unless acted upon by an external force (Correct answer)
- For every action there is an equal and opposite reaction
- Energy cannot be created or destroyed
Correct answer: An object at rest stays at rest unless acted upon by an external force
Newton's First Law is the law of inertia: objects resist changes in their state of motion.
Newton's First Law states that an object at rest remains at rest, and an object in motion remains in motion at the same speed and direction, unless acted upon by an unbalanced external force. This property is called inertia.
Question 2: What is the formula for calculating force?
- F = m/a
- F = ma (Correct answer)
- F = a/m
- F = m + a
Correct answer: F = ma
Newton's Second Law: F = ma (Force equals mass times acceleration).
Force (F) equals mass (m) multiplied by acceleration (a): F = ma. This is Newton's Second Law of Motion. The unit of force in the SI system is the Newton (N), where 1 N = 1 kg·m/s².
Question 3: What is the atomic number of an element?
- Number of neutrons in the nucleus
- Total mass of the atom
- Number of protons in the nucleus (Correct answer)
- Number of electrons in the outer shell
Correct answer: Number of protons in the nucleus
The atomic number equals the number of protons, which defines the element.
The atomic number is the number of protons in the nucleus of an atom. It is unique to each element and determines the element's identity. For a neutral atom, the atomic number also equals the number of electrons.
Question 4: Which of the following is a chemical change?
- Ice melting
- Salt dissolving in water
- Paper burning (Correct answer)
- Glass breaking
Correct answer: Paper burning
Burning produces new substances (ash, CO₂); it is a chemical change.
A chemical change creates new substances with different properties. Burning paper produces carbon dioxide, water vapor, and ash — entirely new materials. Melting, dissolving, and breaking are physical changes that don't alter the chemical composition.
Question 5: What is the speed of light in a vacuum?
- 3 × 10⁶ m/s
- 3 × 10⁸ m/s (Correct answer)
- 3 × 10¹⁰ m/s
- 3 × 10⁴ m/s
Correct answer: 3 × 10⁸ m/s
The speed of light in a vacuum is approximately 3 × 10⁸ meters per second.
Light travels at approximately 299,792,458 m/s in a vacuum, commonly rounded to 3 × 10⁸ m/s. This constant (c) is fundamental to Einstein's theory of relativity and many other physics equations.
Question 6: What is the pH of a neutral solution?
- 0
- 7 (Correct answer)
- 14
- 5
Correct answer: 7
A neutral solution has a pH of 7; acids are below 7, bases are above 7.
The pH scale measures acidity or basicity. A pH of 7 is neutral (pure water). Values below 7 indicate acidic solutions; values above 7 indicate basic (alkaline) solutions.
Question 7: What is the law of conservation of energy?
- Energy can be created from matter
- Energy can neither be created nor destroyed, only converted (Correct answer)
- Energy always decreases over time
- Energy and mass are always equal
Correct answer: Energy can neither be created nor destroyed, only converted
Energy is conserved — it changes form but the total amount remains constant.
The law of conservation of energy states that energy cannot be created or destroyed; it can only be transformed from one form to another. For example, potential energy converts to kinetic energy as an object falls.
Question 8: Which subatomic particle has a negative charge?
- Proton
- Neutron
- Electron (Correct answer)
- Nucleus
Correct answer: Electron
Electrons have a negative charge; protons are positive; neutrons are neutral.
Electrons carry a negative electric charge of -1 and orbit the nucleus. Protons carry a +1 charge and are in the nucleus. Neutrons have no charge. The nucleus is not a particle itself.
Question 9: What type of energy does a compressed spring possess?
- Kinetic energy
- Thermal energy
- Elastic potential energy (Correct answer)
- Chemical energy
Correct answer: Elastic potential energy
A compressed spring stores elastic potential energy, which is released when it decompresses.
Elastic potential energy is stored in objects when they are stretched or compressed. A compressed spring is a classic example. When released, the stored energy converts to kinetic energy.
Question 10: What is the chemical symbol for gold?
- Go
- Gd
- Au (Correct answer)
- Ag
Correct answer: Au
Gold's symbol Au comes from the Latin word 'aurum.'
Au is the chemical symbol for gold, derived from the Latin 'aurum.' Silver is Ag (argentum), Gd is gadolinium. Knowing Latin-derived symbols helps with the periodic table.
Question 11: What happens to gas pressure if volume decreases at constant temperature?
- Pressure decreases
- Pressure stays the same
- Pressure increases (Correct answer)
- Temperature rises
Correct answer: Pressure increases
Boyle's Law: pressure and volume are inversely proportional at constant temperature.
Boyle's Law states that at constant temperature, pressure and volume of a gas are inversely proportional: P₁V₁ = P₂V₂. Decreasing volume squeezes the gas molecules into a smaller space, increasing their collision frequency, and thus pressure rises.
Question 12: What is an isotope?
- An atom with a different number of protons
- An atom with the same number of protons but different neutrons (Correct answer)
- A molecule with extra electrons
- A radioactive element
Correct answer: An atom with the same number of protons but different neutrons
Isotopes are atoms of the same element with different numbers of neutrons.
Isotopes are variants of the same element that have the same atomic number (protons) but different mass numbers due to varying numbers of neutrons. For example, Carbon-12 and Carbon-14 are both carbon but have different neutron counts.
Question 13: What is the term for the minimum energy required to start a chemical reaction?
- Enthalpy
- Activation energy (Correct answer)
- Kinetic energy
- Bond energy
Correct answer: Activation energy
Activation energy is the minimum energy needed to initiate a chemical reaction.
Activation energy is the minimum amount of energy required for reactants to undergo a chemical reaction and form products. Catalysts work by providing an alternative pathway with lower activation energy, speeding up reactions.
Question 14: Which force keeps planets in orbit around the Sun?
- Magnetic force
- Electric force
- Gravitational force (Correct answer)
- Nuclear force
Correct answer: Gravitational force
Gravity provides the centripetal force that keeps planets in orbit.
Gravitational force is the attractive force between any two masses. The Sun's massive gravity pulls planets toward it, providing the centripetal force needed to maintain their orbital paths.
Question 15: What is the process by which a solid changes directly to a gas?
- Condensation
- Evaporation
- Sublimation (Correct answer)
- Fusion
Correct answer: Sublimation
Sublimation is the direct transition from solid to gas without becoming liquid.
Sublimation occurs when a solid absorbs enough energy to transition directly to the gas phase, bypassing the liquid phase. Dry ice (solid CO₂) sublimates at room temperature. The reverse process is called deposition.
Question 16: What unit measures electrical current?
- Volt
- Ohm
- Ampere (Correct answer)
- Watt
Correct answer: Ampere
Electrical current is measured in amperes (amps).
Electrical current (the flow of electric charge) is measured in amperes (A). Voltage (potential difference) is in volts, resistance is in ohms, and power is in watts.
Question 17: What type of bond forms between two nonmetal atoms sharing electrons?
- Ionic bond
- Covalent bond (Correct answer)
- Metallic bond
- Hydrogen bond
Correct answer: Covalent bond
Covalent bonds form when atoms share electrons, common between nonmetals.
A covalent bond forms when two atoms share one or more pairs of electrons. This type of bond is typical between nonmetal atoms. Ionic bonds involve electron transfer (usually metal + nonmetal), and metallic bonds exist in metals.
Question 18: What is the freezing point of water on the Celsius scale?
- 100°C
- 32°C
- 0°C (Correct answer)
- -100°C
Correct answer: 0°C
Water freezes at 0°C (32°F) under standard conditions.
Water freezes at 0°C (32°F) and boils at 100°C (212°F) under standard atmospheric pressure. The Celsius scale is defined using these two reference points.
Question 19: What does the term 'acceleration' mean in physics?
- Speed in a given direction
- Change in speed only
- Rate of change of velocity (Correct answer)
- Distance divided by time
Correct answer: Rate of change of velocity
Acceleration is the rate at which velocity changes over time.
Acceleration is the rate of change of velocity, measured in m/s². Because velocity is a vector (speed + direction), acceleration can result from a change in speed, direction, or both. Formula: a = Δv/Δt.
Question 20: Which state of matter has a definite volume but no definite shape?
- Solid
- Liquid (Correct answer)
- Gas
- Plasma
Correct answer: Liquid
Liquids have a definite volume but take the shape of their container.
Liquids have definite volume because their molecules are close together, but they have no fixed shape — they conform to the shape of their container. Solids have both definite shape and volume; gases have neither.
Question 21: What is the chemical formula for water?
- HO
- H₂O (Correct answer)
- H₂O₂
- OH
Correct answer: H₂O
Water consists of two hydrogen atoms bonded to one oxygen atom: H₂O.
Water (H₂O) is composed of two hydrogen atoms covalently bonded to one oxygen atom. H₂O₂ is hydrogen peroxide (one extra oxygen), HO is a free radical, and OH is the hydroxide ion.
Question 22: What property of a wave determines its pitch when heard as sound?
- Amplitude
- Wavelength
- Frequency (Correct answer)
- Speed
Correct answer: Frequency
Frequency determines pitch: higher frequency = higher pitch.
Frequency is the number of wave cycles per second (measured in hertz, Hz). In sound, higher frequency means the sound wave oscillates more rapidly, producing a higher pitch. Amplitude determines loudness, not pitch.
Question 23: What is the main difference between an acid and a base?
- Acids contain oxygen; bases do not
- Acids donate hydrogen ions (H⁺); bases accept them (Correct answer)
- Acids are liquid; bases are solid
- Acids are found in food only
Correct answer: Acids donate hydrogen ions (H⁺); bases accept them
Acids donate H⁺ ions; bases accept H⁺ ions (or donate OH⁻).
According to the Brønsted-Lowry definition, acids are proton (H⁺) donors and bases are proton acceptors. Acids have pH < 7; bases have pH > 7. Common acids include HCl and vinegar; common bases include NaOH and baking soda.
Question 24: What is kinetic energy?
- Energy stored due to position
- Energy of motion (Correct answer)
- Energy released in chemical reactions
- Heat energy
Correct answer: Energy of motion
Kinetic energy is the energy an object possesses due to its motion.
Kinetic energy (KE) is the energy of a moving object. The formula is KE = ½mv², where m is mass and v is speed. Stored energy based on position is potential energy.
Question 25: What is the function of a catalyst in a chemical reaction?
- It is consumed in the reaction
- It slows the reaction rate
- It speeds up the reaction without being used up (Correct answer)
- It changes the products formed
Correct answer: It speeds up the reaction without being used up
A catalyst speeds up a reaction by lowering activation energy and is not consumed.
A catalyst increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy. Critically, it is not consumed in the process, so it can catalyze multiple reaction cycles.
Question 26: What law states that the total momentum of a closed system is conserved?
- Law of conservation of energy
- Newton's First Law
- Law of conservation of momentum (Correct answer)
- Boyle's Law
Correct answer: Law of conservation of momentum
The law of conservation of momentum states that total momentum in a closed system remains constant.
The law of conservation of momentum states that the total momentum of a system remains constant if no external forces act on it. In a collision, the total momentum before equals the total momentum after.
Question 27: What is an element?
- A compound made of two atoms
- A pure substance made of only one type of atom (Correct answer)
- A mixture of gases
- A type of molecule
Correct answer: A pure substance made of only one type of atom
An element consists entirely of one type of atom and cannot be broken down chemically.
An element is a pure substance consisting of only one type of atom, identified by its atomic number. Elements cannot be broken down into simpler substances by ordinary chemical means. There are 118 known elements.
Question 28: What happens to the resistance of a conductor as its temperature increases?
- Resistance decreases
- Resistance stays the same
- Resistance increases (Correct answer)
- Resistance becomes zero
Correct answer: Resistance increases
For most conductors, resistance increases with temperature as atomic vibrations impede electron flow.
In most metallic conductors, increasing temperature causes atoms to vibrate more vigorously, impeding the flow of electrons and increasing electrical resistance. Semiconductors behave oppositely — their resistance decreases with temperature.
Question 29: What is the periodic table organized by?
- Alphabetical order
- Atomic mass only
- Increasing atomic number (Correct answer)
- Reactivity
Correct answer: Increasing atomic number
Elements are arranged in order of increasing atomic number (number of protons).
The modern periodic table arranges elements in order of increasing atomic number (number of protons). This arrangement places elements with similar chemical properties in the same vertical columns (groups or families).
Question 30: What type of radiation can be stopped by a sheet of paper?
- Beta radiation
- Gamma radiation
- Alpha radiation (Correct answer)
- X-rays
Correct answer: Alpha radiation
Alpha particles are large and easily stopped by paper or even skin.
Alpha radiation consists of large particles (2 protons + 2 neutrons) that have low penetrating power and can be blocked by a sheet of paper or a few centimeters of air. Beta particles require thicker shielding (plastic or aluminum), and gamma rays need dense materials like lead.
Question 31: What is the relationship between wavelength and frequency in electromagnetic waves?
- They are directly proportional
- They are inversely proportional (Correct answer)
- They are always equal
- They are unrelated
Correct answer: They are inversely proportional
Higher frequency waves have shorter wavelengths: c = fλ.
For electromagnetic waves, speed (c) = frequency (f) × wavelength (λ). Since c is constant (~3×10⁸ m/s), frequency and wavelength are inversely proportional: as frequency increases, wavelength decreases and vice versa.
Question 32: Which form of energy is released when fuel burns in an engine?
- Nuclear energy
- Chemical energy converted to heat and mechanical energy (Correct answer)
- Solar energy
- Magnetic energy
Correct answer: Chemical energy converted to heat and mechanical energy
Combustion converts chemical energy stored in fuel to heat and mechanical energy.
Burning fuel is a chemical reaction (combustion) that converts chemical potential energy stored in bonds into thermal energy and mechanical energy. An engine harnesses that thermal energy to perform work.
Question 33: What is ohm's law?
- V = IR (Correct answer)
- P = IV
- F = ma
- E = mc²
Correct answer: V = IR
Ohm's Law: Voltage (V) = Current (I) × Resistance (R).
Ohm's Law states that the voltage (V) across a conductor equals the current (I) flowing through it multiplied by its resistance (R): V = IR. It is fundamental to circuit analysis.
Question 34: What is the difference between a physical and a chemical property?
- Physical properties involve reactions; chemical do not
- Physical properties can be observed without changing composition; chemical properties describe reaction behavior (Correct answer)
- They are the same thing
- Only chemical properties can be measured
Correct answer: Physical properties can be observed without changing composition; chemical properties describe reaction behavior
Physical properties (color, density) don't change composition; chemical properties describe reactivity.
Physical properties (e.g., melting point, density, color) can be observed or measured without changing the substance's chemical identity. Chemical properties describe how a substance behaves in chemical reactions — for example, flammability or ability to rust.
Question 35: What is the half-life of a radioactive substance?
- The time it takes to fully decay
- The time for half the atoms to decay (Correct answer)
- The energy released during decay
- The rate of radiation emission
Correct answer: The time for half the atoms to decay
Half-life is the time required for half of the radioactive atoms in a sample to decay.
Half-life is the time it takes for half of the radioactive nuclei in a sample to undergo radioactive decay. After one half-life, 50% remains; after two, 25%; after three, 12.5%, and so on.
Question 36: Which of the following best describes a mixture?
- A pure substance with one type of molecule
- Two or more substances combined but not chemically bonded (Correct answer)
- A compound formed through a chemical reaction
- A single element in liquid form
Correct answer: Two or more substances combined but not chemically bonded
A mixture contains two or more substances that can be separated by physical means.
A mixture is a combination of two or more substances that retain their individual properties and can be separated by physical means (filtering, evaporation, etc.). Unlike compounds, the components are not chemically bonded together.
ASVAB General Science: Physics and Chemistry Concepts
What is Newton's First Law of Motion?