GED Science 2 — Questions and Answers

Question 1: According to Newton's Second Law of Motion, what happens to the acceleration of an object if the force applied to it is doubled while the mass stays the same?

Acceleration is halved
Acceleration stays the same
Acceleration doubles (Correct answer)
Acceleration quadruples

Correct answer: Acceleration doubles

Newton's Second Law: F = ma, or a = F/m. If force doubles and mass is constant, acceleration doubles.

Newton's Second Law of Motion states that the net force on an object equals its mass times its acceleration: F = ma. Rearranging: a = F/m If force (F) is doubled while mass (m) stays constant: a = (2F)/m = 2 × (F/m) = 2a The acceleration doubles. Force and acceleration are directly proportional when mass is constant. Conversely, if mass is doubled while force stays constant, acceleration halves (inverse relationship between mass and acceleration). Practical examples: • Pushing the same box with twice the force makes it accelerate twice as fast • A heavier (more massive) box requires more force to achieve the same acceleration Newton's Three Laws: 1. Inertia: objects at rest stay at rest; objects in motion stay in motion unless acted on by a net force 2. F = ma 3. Every action has an equal and opposite reaction

Question 2: What is the difference between a physical change and a chemical change?

A physical change alters the substance's chemical composition; a chemical change does not
A chemical change produces a new substance; a physical change does not alter chemical composition (Correct answer)
Physical changes are irreversible; chemical changes can be reversed
Chemical changes only involve temperature; physical changes involve shape

Correct answer: A chemical change produces a new substance; a physical change does not alter chemical composition

A chemical change creates new substances with different chemical properties (e.g., burning wood). A physical change alters form or appearance but not chemical composition (e.g., cutting wood).

Physical change: alters the form, shape, or state of matter WITHOUT changing its chemical composition. Examples: cutting paper, melting ice, dissolving sugar in water, boiling water, crumpling aluminum foil. Key: the chemical identity remains the same (H₂O is still H₂O whether liquid or gas). Often reversible (ice melts → can refreeze). Chemical change: produces one or more new substances with DIFFERENT chemical properties. Examples: burning wood, rusting iron, cooking an egg, vinegar + baking soda reaction, photosynthesis. Signs of chemical change: gas produced, color change, precipitate forms, temperature change, light produced. Often irreversible (burned wood cannot be 'unburned'). Note: dissolving sugar seems like a chemical change but is physical — sugar molecules remain unchanged and can be recovered by evaporating the water. Dissolving sugar in water ≠ cooking sugar (which IS a chemical change).

Question 3: Which statement correctly describes the conservation of mass?

Mass is created during chemical reactions when new substances form
Mass is destroyed when substances are burned or decomposed
The total mass of reactants equals the total mass of products in a chemical reaction (Correct answer)
Mass changes depending on the temperature and pressure of the reaction

Correct answer: The total mass of reactants equals the total mass of products in a chemical reaction

The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction — the total mass of reactants always equals the total mass of products.

The Law of Conservation of Mass, established by Antoine Lavoisier in 1789, states: in any chemical reaction, the total mass of the reactants equals the total mass of the products. Basis: during a chemical reaction, atoms are rearranged — bonds break and new bonds form — but no atoms are created or destroyed. Since mass depends on the number and type of atoms, total mass is conserved. Example: burning methane CH₄ + 2O₂ → CO₂ + 2H₂O Mass of CH₄ + O₂ = Mass of CO₂ + H₂O Why burning wood seems to lose mass: some products (CO₂, H₂O vapor) escape into the air as gases. If you could capture ALL products, the total mass would equal the original mass of wood + oxygen used. This law is foundational to stoichiometry (quantitative chemistry) — it's why chemical equations must be balanced.

Question 4: What type of wave is a sound wave?

Transverse wave
Electromagnetic wave
Longitudinal wave (Correct answer)
Surface wave

Correct answer: Longitudinal wave

Sound is a longitudinal wave — the medium's particles vibrate parallel to the direction of wave travel, creating alternating compressions and rarefactions.

Waves transfer energy through matter or space. The two main types are: Transverse waves: particles vibrate PERPENDICULAR to the direction of wave travel. Examples: light waves, electromagnetic waves, waves on a string, water surface waves. Visualize: a rope waved up and down while the wave moves sideways. Longitudinal waves: particles vibrate PARALLEL to the direction of wave travel. Examples: sound waves, P-waves (seismic), waves in a Slinky pushed lengthwise. Visualize: a Slinky compressed and released — compressions (high density) and rarefactions (low density) travel along it. Sound specifically: • Requires a medium (cannot travel through vacuum → no sound in space) • Speed depends on medium: fastest in solids, slower in liquids, slowest in gases • Sound in air at room temperature: ~343 m/s • Light waves (electromagnetic) travel 880,000 times faster than sound in air — why we see lightning before hearing thunder

Question 5: An atom has 8 protons, 8 neutrons, and 8 electrons. What element is this, and what is its atomic mass?

Nitrogen with atomic mass 7
Oxygen with atomic mass 16 (Correct answer)
Neon with atomic mass 20
Carbon with atomic mass 12

Correct answer: Oxygen with atomic mass 16

The atomic number (number of protons) = 8 identifies the element as Oxygen (O). Atomic mass ≈ protons + neutrons = 8 + 8 = 16.

Key atomic concepts: • Protons: positively charged particles in the nucleus; the NUMBER OF PROTONS defines the element (atomic number). 8 protons = Oxygen (O). • Neutrons: neutral particles in the nucleus; contribute to atomic mass but not atomic number. • Electrons: negatively charged particles orbiting the nucleus; number = protons in a neutral atom (8 electrons = 8 protons, so this is a neutral oxygen atom). • Atomic number = number of protons = 8 (this IS the element's identity — changing protons changes the element) • Atomic mass ≈ protons + neutrons = 8 + 8 = 16 atomic mass units (amu) Oxygen (O) on the periodic table: atomic number 8, atomic mass ~16. Isotopes: atoms of the same element with different numbers of neutrons. Oxygen-17 has 8 protons + 9 neutrons; Oxygen-18 has 8 protons + 10 neutrons. All are still oxygen because they have 8 protons.

Question 6: A student pushes a 10 kg box across a floor with a force of 50 N. The box does not move. What can you conclude?

The box has no friction force acting on it
The friction force equals or exceeds 50 N (Correct answer)
There is a net force of 50 N on the box
The box's weight equals 50 N

Correct answer: The friction force equals or exceeds 50 N

If the box doesn't move, it's in equilibrium — net force = 0. This means friction must be at least equal to the applied force (50 N) to prevent motion.

Newton's First Law (Inertia): An object at rest stays at rest unless acted on by a NET force. If the box doesn't move, the net force is zero. Forces acting on the box horizontally: • Applied force: 50 N (pushing the box) • Static friction force: opposes the applied force Since net force = 0: 50 N (applied) − friction force = 0 Friction force = 50 N (at minimum) Static friction (when object is stationary) adjusts to match and oppose applied force, up to its maximum value. Only when the applied force EXCEEDS maximum static friction does the object start moving. The box's weight = mg = 10 kg × 9.8 m/s² ≈ 98 N (not 50 N as stated in option D). Real-world implication: to move the box, you'd need to apply a force greater than the maximum static friction force.

GED Science 2

According to Newton's Second Law of Motion, what happens to the acceleration of an object if the force applied to it is doubled while the mass stays the same?