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Science Flashcards

6 cards from real GED practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Science flashcards as text

  1. A researcher notices that a population of bacteria doubles every 20 minutes under optimal conditions. If a culture starts with 500 bacteria, approximately how many will be present after 2 hours?

    Answer: 32,000

    2 hours = 120 minutes. At 20 minutes per doubling, that's 6 doubling periods. 500 × 2⁶ = 500 × 64 = 32,000. Each doubling multiplies the population by 2, so after 6 doublings the count is 500 × 64.

  2. During a chemical reaction, the temperature of the reaction vessel drops significantly. Which of the following best explains this observation?

    Answer: The reaction is endothermic and absorbs heat from the surroundings.

    A drop in vessel temperature indicates heat is being absorbed by the reaction from its surroundings — the definition of an endothermic reaction. Exothermic reactions release heat, causing the surroundings to warm. Catalysts do not lower temperature, and activation energy describes the energy barrier, not whether heat is absorbed or released.

  3. A rock sample contains equal amounts of a radioactive parent isotope and its stable daughter isotope. If the half-life of the parent isotope is 1.4 billion years, how old is the rock?

    Answer: 1.4 billion years

    When parent and daughter isotopes are present in a 1:1 ratio, exactly half of the original parent material has decayed. This means exactly one half-life has elapsed. Since the half-life is 1.4 billion years, the rock is 1.4 billion years old.

  4. Two objects are moving toward each other in space with no external forces acting on them. Object A has a mass of 4 kg and a velocity of 3 m/s east. Object B has a mass of 2 kg and a velocity of 6 m/s west. After they collide and stick together, what is the velocity of the combined object?

    Answer: 0 m/s (stationary)

    Using conservation of momentum: total momentum before = (4 kg × 3 m/s east) + (2 kg × −6 m/s east) = 12 − 12 = 0 kg·m/s. Since total momentum is zero before the collision, the combined object has zero momentum after and remains stationary.

  5. Which cellular process directly produces ATP through a series of electron carriers embedded in the inner mitochondrial membrane?

    Answer: The electron transport chain

    The electron transport chain (oxidative phosphorylation) uses protein complexes embedded in the inner mitochondrial membrane to pass electrons and pump protons, driving ATP synthase to produce the majority of a cell's ATP. Glycolysis occurs in the cytoplasm and produces only 2 ATP net. The Krebs cycle produces NADH/FADH₂ but little direct ATP. Fermentation regenerates NAD⁺ without net ATP gain.

  6. A scientist measures the pH of four solutions: W = 2, X = 6, Y = 8, Z = 11. Which statement correctly compares the hydrogen ion concentrations of these solutions?

    Answer: Solution W has 10,000 times more hydrogen ions than Solution X.

    pH is a logarithmic scale; each unit represents a 10-fold change in hydrogen ion concentration. Solution W (pH 2) and Solution X (pH 6) differ by 4 pH units, meaning W has 10⁴ = 10,000 times more hydrogen ions than X. Solution X is not simply 'twice' as acidic — that misunderstands the logarithmic nature of pH. Solution Y has fewer hydrogen ions than X, not more. Solution Z (pH 11) actually has the lowest hydrogen ion concentration among all four.