99+ Free Encceja Ensino Médio Practice Questions

Explanation: Electrical energy consumption is calculated using the formula E = P × Δt, where P is power in kilowatts (kW) and Δt is the operating time in hours (h). For the electric shower: E_shower = 5.5 kW × 1 h/day × 30 days = 165 kWh/month. For the refrigerator: E_refrigerator = 0.2 kW × 10 h/day × 30 days = 60 kWh/month. Therefore, the electric shower consumes significantly more monthly energy (165 kWh vs. 60 kWh), making shower duration the most critical factor in household electricity bills.

Explanation: In conventional water treatment, the addition of coagulants such as aluminum sulfate neutralizes surface charges on suspended particles, allowing them to clump together into larger flocs (coagulation and flocculation). Next, the water moves slowly through sedimentation tanks where these heavy flocs settle by gravity to the bottom of the basin (decantation/sedimentation), preparing the clarified water for filtration and chemical disinfection (chlorination and fluoridation).

Explanation: Heat transfer occurs via three fundamental mechanisms: conduction (direct molecular kinetic transfer through matter), convection (bulk fluid movement driven by density gradients), and radiation (electromagnetic infrared emission). The mirrored silver surfaces inside a thermal flask reflect infrared electromagnetic waves back toward the liquid (or away from it), thereby minimizing radiative heat exchange. In contrast, the vacuum gap prevents conduction and convection, and the stopper prevents convective vapor loss.

Explanation: In a series circuit, the total voltage of the source (127 V) is divided equally among identical resistors: V_each = 127 V / 3 ≈ 42.3 V. Because electric power is proportional to the square of voltage (P = V²/R), operating at one-third of the rated voltage causes the bulbs to emit very dim light. Furthermore, in a series circuit, there is only a single path for current flow; if any single bulb is unscrewed or burns out, the circuit is broken and all bulbs extinguish. In contrast, standard household wiring uses parallel circuits where each appliance receives full line voltage (127 V) independently.

Explanation: The core distinction in immunology is active vs. passive immunization. A serum (soro) is a curative agent containing pre-formed antibodies (produced in another organism, such as a horse) that neutralize active toxins immediately, providing fast-acting but temporary passive immunity without creating immunological memory. In contrast, a vaccine (vacina) contains attenuated or inactivated antigens (or mRNA) that stimulate the patient's own immune system to generate antibodies and durable memory B and T cells (active immunity) to prevent future disease.

Explanation: Eutrophication (eutrofização) is an ecological process resulting from the excessive enrichment of water bodies with nutrients—predominantly nitrogen and phosphorus compounds from raw sewage and agricultural fertilizers. This leads to explosive proliferation of surface microalgae and cyanobacteria (algal bloom). When these algae die, aerobic decomposer bacteria multiply rapidly, consuming virtually all dissolved oxygen (DO) in the water. The resulting severe hypoxia or anoxia leads to massive fish kills and foul-smelling anaerobic decomposition.

Explanation: According to Newton's First Law of Motion (the Principle of Inertia), a body at rest remains at rest, and a body in uniform rectilinear motion continues moving with constant velocity unless compelled to change that state by a net external force. When a car's brakes apply friction to the wheels, the vehicle slows down; however, the passenger's body tends to continue moving forward at the vehicle's prior speed due to inertia. The seatbelt applies the necessary external restraining force to safely decelerate the passenger along with the vehicle.

Explanation: In oxygenic photosynthesis, chloroplasts use light energy to build energy-rich organic matter from carbon dioxide and water. A common summary equation is 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂, although the pathway proceeds through separate light reactions and carbon-fixation reactions.

Explanation: A chemical transformation (or chemical reaction) involves the rearrangement of chemical bonds to form one or more new substances with distinct chemical and physical properties from the original reactants. The formation of rust on iron involves an oxidation-reduction reaction between iron metal (Fe), oxygen (O₂), and water (H₂O) to produce hydrated iron(III) oxide (Fe₂O₃·nH₂O), creating a completely new chemical compound. In contrast, melting ice, crushing salt, and dissolving sugar are physical changes because the molecular identities (H₂O, NaCl, C₁₂H₂₂O₁₁) remain unchanged.

Explanation: Dengue, Zika, and Chikungunya are viral infections transmitted to humans primarily through the bite of infected female *Aedes aegypti* mosquitoes. The mosquito reproduces by laying eggs on the inner walls of containers holding clean, stagnant standing water (such as discarded tires, flowerpot plates, uncovered water tanks, and clogged rain gutters). Eliminating these aquatic breeding habitats breaks the mosquito's reproductive larval cycle, reducing vector populations and preventing viral spread.