Scientific Laws Practice Questions
20 free Scientific Laws practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following layers of the Earth's atmosphere contains the ozone layer that protects life from ultraviolet radiation?
- A Troposphere
- B Stratosphere
- C Mesosphere
- D Thermosphere
Correct answer: Stratosphere
The stratosphere houses the ozone layer, which absorbs the majority of the Sun's harmful ultraviolet (UV) radiation. This layer is situated above the troposphere and below the mesosphere.
What is the primary gas that makes up approximately 78% of the Earth's atmosphere?
- A Oxygen
- B Carbon Dioxide
- C Nitrogen
- D Argon
Correct answer: Nitrogen
Nitrogen is the most abundant gas in the Earth's atmosphere, followed by oxygen at about 21%. Other gases like argon and carbon dioxide exist in much smaller trace amounts.
In the human body, which organ is primarily responsible for the filtration of blood and the removal of metabolic waste?
- A Liver
- B Spleen
- C Adrenal gland
- D Kidneys
Correct answer: Kidneys
The kidneys filter blood to remove urea, salts, and excess water, which are then excreted as urine. This process is essential for maintaining the body's chemical balance and blood pressure.
Which physical law states that for every action, there is an equal and opposite reaction?
- A Newton's First Law
- B Newton's Second Law
- C Newton's Third Law
- D Law of Universal Gravitation
Correct answer: Newton's Third Law
Newton's Third Law of Motion describes how forces always exist in pairs; if object A exerts a force on object B, object B exerts an equal and opposite force on object A. This principle is fundamental to understanding motion and propulsion.
What is the pH value of pure water at standard room temperature?
- A pH 5
- B pH 14
- C pH 7
- D pH 9
Correct answer: pH 7
Pure water has a pH of 7, placing it at the exact midpoint of the pH scale, which runs from 0 (most acidic) to 14 (most alkaline). At this value, the concentrations of hydrogen ions and hydroxide ions are equal, making water a perfectly neutral substance.
Which subatomic particle carries a negative electrical charge and orbits the nucleus of an atom?
- A Proton
- B Neutron
- C Electron
- D Positron
Correct answer: Electron
Electrons are negatively charged particles that occupy specific energy levels or shells around the atom's nucleus. Their arrangement and interactions determine the chemical properties of an element.
By which process do green plants convert sunlight into chemical energy in the form of glucose?
- A Cellular respiration
- B Transpiration
- C Photosynthesis
- D Fermentation
Correct answer: Photosynthesis
Photosynthesis occurs in the chloroplasts of plant cells, using sunlight, carbon dioxide, and water to produce oxygen and energy-rich carbohydrates. This process is the foundation of energy for most life on Earth.
Which type of mirror is commonly used as a rear-view mirror in vehicles to provide a wider field of view?
- A Concave mirror
- B Convex mirror
- C Plane mirror
- D Parabolic mirror
Correct answer: Convex mirror
Convex mirrors bulge outward, causing light rays to diverge and creating a diminished, upright image. This allows the driver to see a larger area than a flat or concave mirror would permit.
Which of the following vitamin deficiencies is the leading cause of Scurvy?
- A Vitamin A
- B Vitamin B12
- C Vitamin C
- D Vitamin D
Correct answer: Vitamin C
Vitamin C (ascorbic acid) is essential for the synthesis of collagen in the human body. A severe lack of this vitamin leads to Scurvy, characterized by bleeding gums and poor wound healing.
What is the SI unit of electric current?
- A Volt
- B Coulomb
- C Ampere
- D Watt
Correct answer: Ampere
The Ampere, often shortened to 'amp', measures the flow of electric charge through a surface at the rate of one coulomb per second. It is one of the seven base SI units.
Which element is known as the 'building block of life' because it can form stable bonds with many elements, including itself?
- A Hydrogen
- B Oxygen
- C Carbon
- D Nitrogen
Correct answer: Carbon
Carbon's ability to form four covalent bonds allows it to create complex, long-chain molecules like DNA and proteins. This versatility makes it the central element of organic chemistry.
Which part of the human brain is primarily responsible for regulating balance, posture, and muscle coordination?
- A Cerebrum
- B Cerebellum
- C Medulla Oblongata
- D Thalamus
Correct answer: Cerebellum
The cerebellum, located at the back of the brain, processes sensory input and coordinates voluntary movements. It ensures that movements are smooth and precise rather than jerky.
Sound waves travel fastest through which of the following media?
- A Vacuum
- B Air
- C Water
- D Steel
Correct answer: Steel
Sound is a mechanical wave that requires a medium to travel; it travels faster in solids than in liquids or gases due to the higher density and elasticity of the particles. Steel, being a dense solid, transmits sound significantly faster than air or water.
What is the phenomenon called when light changes direction as it passes from one transparent medium to another?
- A Reflection
- B Refraction
- C Diffraction
- D Dispersion
Correct answer: Refraction
Refraction occurs because light travels at different speeds in different materials. When light enters a medium with a different refractive index at an angle, it bends toward or away from the normal line.
Which of the following is an example of a chemical change?
- A Melting of ice
- B Dissolving sugar in water
- C Rusting of iron
- D Boiling of water
Correct answer: Rusting of iron
Rusting is a chemical reaction between iron, oxygen, and moisture that forms a new substance (iron oxide). The other options are physical changes where the molecular structure of the substance remains the same.
The process by which a solid changes directly into a gas without passing through the liquid state is known as:
- A Evaporation
- B Condensation
- C Sublimation
- D Deposition
Correct answer: Sublimation
Sublimation occurs when the vapor pressure of a solid is high enough for it to transition directly to a gas. Common examples include dry ice (solid carbon dioxide) and mothballs.
Which planet in our solar system is often referred to as the 'Red Planet' due to the presence of iron oxide on its surface?
- A Venus
- B Mars
- C Jupiter
- D Saturn
Correct answer: Mars
Mars has a reddish appearance because its surface is covered in iron oxide, similar to rust. It is the fourth planet from the Sun and has long been a primary target for space exploration.
In a biological cell, which organelle is known as the 'powerhouse' because it generates most of the cell's supply of ATP?
- A Nucleus
- B Ribosome
- C Mitochondria
- D Endoplasmic Reticulum
Correct answer: Mitochondria
Mitochondria perform cellular respiration, converting nutrients into adenosine triphosphate (ATP). ATP serves as the primary energy currency for the cell's metabolic activities.
What is the term for a substance that increases the rate of a chemical reaction without being consumed in the process?
- A Solvent
- B Reactant
- C Catalyst
- D Inhibitor
Correct answer: Catalyst
A catalyst works by providing an alternative reaction pathway with a lower activation energy. In biological systems, these catalysts are typically proteins called enzymes.
Which scale is used to measure the magnitude of an earthquake based on the seismic waves it produces?
- A Celsius scale
- B Richter scale
- C Beaufort scale
- D Kelvin scale
Correct answer: Richter scale
The Richter scale is a logarithmic scale that quantifies the energy released during an earthquake. While the Moment Magnitude Scale is more common today for large quakes, the Richter scale remains the classic reference for general scientific awareness.