ASVAB General Science Practice Test

Explanation: Weathering is the breakdown of rocks into smaller pieces by physical, chemical, or biological processes. Erosion is the transport of those weathered materials to a new location.

Explanation: The cell membrane (also called the plasma membrane) is a selectively permeable barrier that controls what substances can enter and exit the cell, maintaining the cell's internal environment.

Explanation: Friction is the force that resists the sliding or rolling of one solid object over another. It is caused by the roughness of the surfaces in contact and acts in the opposite direction of motion.

Explanation: Vitamin D is synthesized in the skin when it is exposed to ultraviolet B (UVB) rays from sunlight. This vitamin is essential for calcium absorption and bone health.

Explanation: The nucleus of an atom contains protons (positively charged) and neutrons (no charge). Electrons (negatively charged) orbit around the nucleus in electron shells.

Explanation: Evaporation is the process by which a liquid changes into a gas. This occurs when molecules at the surface of a liquid gain enough energy to escape into the air as vapor.

Explanation: Sound travels fastest through solids because their molecules are closest together, allowing vibrations to transfer more quickly. Sound cannot travel through a vacuum at all because there are no molecules to vibrate.

Explanation: Copper is an excellent conductor of electricity because its electrons can move freely. This is why copper is commonly used in electrical wiring. Rubber, plastic, and wood are insulators.

Explanation: A lever is a simple machine consisting of a rigid bar (lever arm) that rotates around a fixed point called the fulcrum. Levers make work easier by multiplying force or changing the direction of force.

Explanation: Liquids have a definite volume but take the shape of their container. Solids have both definite volume and shape, while gases have neither definite volume nor shape.

Explanation: The pH scale ranges from 0 to 14 and measures how acidic or basic (alkaline) a substance is. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic.

Explanation: When water freezes, the molecules arrange themselves into a crystalline structure that takes up more space than liquid water. This is why ice floats and why frozen water can burst pipes.

Explanation: Newton's First Law, also known as the law of inertia, states that an object in motion stays in motion and an object at rest stays at rest unless acted upon by an external force.

Explanation: Water's chemical formula is H₂O, meaning each water molecule consists of two hydrogen atoms bonded to one oxygen atom.

Explanation: Mars is called the "Red Planet" because of its reddish appearance, which is caused by iron oxide (rust) on its surface. It is the fourth planet from the Sun.

Explanation: Fossilization is the process of preserving organisms in rock and is not part of the water cycle. The water cycle includes evaporation, condensation, precipitation, and collection.

Explanation: Most earthquakes are caused by the sudden movement of tectonic plates along fault lines. When stress builds up between plates and is suddenly released, it creates seismic waves that shake the ground.

Explanation: Nitrogen makes up about 78% of Earth's atmosphere, while oxygen comprises about 21%. The remaining 1% includes argon, carbon dioxide, and other trace gases.

Explanation: A full moon occurs when Earth is between the Sun and the Moon, and the entire face of the moon facing Earth is illuminated by sunlight.

Explanation: Clouds form when water vapor in the air cools and condenses around tiny particles (dust, pollen, etc.) to form water droplets or ice crystals. This typically happens when warm, moist air rises and cools.

Explanation: The inner core is the innermost layer of Earth, composed primarily of solid iron and nickel. It has extremely high temperatures (over 9,000°F) and tremendous pressure.

Explanation: There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was reclassified as a dwarf planet in 2006.

Explanation: Igneous rocks form when molten rock (magma or lava) cools and solidifies. Examples include granite (cooled underground) and basalt (cooled at the surface).

Explanation: Earth's seasons are caused by the 23.5-degree tilt of its axis. As Earth orbits the Sun, different parts of the planet receive varying amounts of direct sunlight, creating seasonal changes.

Explanation: Leaves contain chloroplasts with chlorophyll, the green pigment that captures sunlight for photosynthesis. The broad, flat structure of leaves maximizes light absorption.

Explanation: The circulatory system, which includes the heart, blood vessels, and blood, transports oxygen from the lungs to cells throughout the body and carries carbon dioxide back to the lungs for removal.

Explanation: The cell is the basic structural and functional unit of all living organisms. It is the smallest unit that can carry out all the processes of life independently.

Explanation: Producers, such as plants and algae, create their own food through photosynthesis. They form the base of the food chain and provide energy for all other organisms.

Explanation: Penguins are birds, not mammals. Although whales, bats, and dolphins may seem unusual, they are all mammals because they have hair, produce milk for their young, and are warm-blooded.

Explanation: DNA stands for Deoxyribonucleic Acid. It is the molecule that carries genetic information in all living organisms and contains the instructions needed for an organism to develop, survive, and reproduce.

Explanation: O negative blood can be given to anyone regardless of their blood type because it lacks A, B, and Rh antigens that could cause an immune reaction. This makes O negative donors especially valuable in emergency situations.

Explanation: Photosynthesis is the process by which plants use sunlight, carbon dioxide, and water to produce glucose (food) and oxygen. This occurs primarily in the leaves.

Explanation: Mitochondria are known as the "powerhouses of the cell" because they produce ATP (adenosine triphosphate), which is the cell's main energy source through cellular respiration.

Explanation: The kidneys filter blood to remove waste products and excess water, which are then excreted as urine. Each person has two kidneys that process about 200 quarts of blood daily.