GED Science Practice Test 1

The passage says every group's meals "contained the same number of Calories and the same amounts of potassium, fat and fiber" and that "The only planned difference between the groups was the amount of sodium."

Step by step:

1. The independent variable (the factor the researchers changed on purpose) is the amount of sodium per day.
2. The dependent variable (what they measured) is systolic blood pressure.
3. Calories, potassium, fat and fiber could also affect blood pressure. Keeping them the same in every group makes them controlled variables.
4. If only sodium differs, a difference in blood pressure between groups can be linked to sodium, not to something else in the diet.

Correct answer: so that any difference in blood pressure between the groups could be linked to sodium and not to other parts of the diet.

Tip: In a fair test, everything except the independent variable is kept the same. When a question asks why something was kept constant, the answer is almost always "to rule out other explanations for the results."

Read the change in each row of the table:

Step by step:

1. Calculate each change: 129 - 136 = -7, 132 - 135 = -3, 136 - 136 = 0.
2. The pattern: the less sodium a group ate, the more its average pressure dropped.
3. Check the other choices against the data: the high group did not rise, potassium was the same in all groups, and the study only included 120 adults for 4 weeks.

Correct answer: among these volunteers, the lower a group's sodium intake, the more its average systolic pressure dropped.

Tip: The best-supported conclusion stays inside the data: the people, the time span and the variables actually tested. Be suspicious of words like cure, anyone and always.

The passage says "The total energy an appliance uses depends on both its power and how long it runs." So power alone cannot tell which appliance uses the most energy.

Step by step:

1. Oven (table: 2,400 W, 1 h): E = \dfrac{2400 \times 1}{1000} = 2.4 kWh per day.
2. Space heater (table: 1,500 W, 4 h): E = \dfrac{1500 \times 4}{1000} = 6.0 kWh per day.
3. Ana is right that the oven has the greatest power, but power is a rate. The heater runs four times as long, so it uses more energy.

Correct answer: Ben is correct for these usage times, because energy depends on both power and time, and the heater uses 6.0 kWh per day compared with the oven's 2.4 kWh.

Tip: When two claims conflict, look for the hidden difference in what each person is measuring: here, rate (power) versus total amount (energy).

From the table: the incandescent bulb uses 60 W and the LED bulb uses 9 W, each for 5 hours per day.

Step by step:

1. Incandescent: E = \dfrac{60 \times 5}{1000} = 0.3 kWh per day.
2. LED: E = \dfrac{9 \times 5}{1000} = 0.045 kWh per day.
3. Savings: 0.3 - 0.045 = 0.255 kWh per day.

(Shortcut: the power difference is 60 - 9 = 51 W, and \dfrac{51 \times 5}{1000} = 0.255 kWh.)

Correct answer: 0.255 kWh.

Tip: In energy problems, check that your answer has the right units and the right size. Forgetting to divide by 1,000 gives watt-hours (255), and forgetting the hours gives only the power difference in kilowatts (0.051).

The diagram shows two arrows leaving the incandescent bulb: 10 J light and 90 J thermal energy (heat). So the 90 J that does not become light is changed into thermal energy.

Step by step:

1. Energy in: 100 J of electrical energy.
2. Energy out: 10 J of light + 90 J of thermal energy = 100 J.
3. Energy in = energy out. This is the law of conservation of energy: energy changes form, but it is not created or destroyed.
4. The thermal energy warms the bulb and the air around it, which is why incandescent bulbs feel hot.

Correct answer: it is changed into thermal energy (heat) that warms the bulb and its surroundings.

Tip: On energy-flow diagrams, the outputs always add up to the input. "Wasted" energy is not destroyed; it usually leaves as heat.

The passage says: "After the front passes, the air pressure rises, the temperature drops quickly, and the wind shifts direction." So look for the period where pressure stops falling and starts rising and temperature drops sharply.

Step by step:

1. Pressure: lowest at 3 PM (1000 hPa), then up to 1006 hPa at 6 PM → it starts rising between 3 PM and 6 PM.
2. Temperature: 20 °C at 3 PM → 12 °C at 6 PM, a drop of 8 °C. This is the biggest 3-hour drop on the graph (the next period drops only 3 °C, from 12 to 9).
3. Both signs of a passing front happen between 3 PM and 6 PM.

Correct answer: between 3 PM and 6 PM.

Tip: When a question gives you a rule in the text ("after X, A and B happen"), turn it into a checklist and test each interval on the graph against every part of the rule.

Acceleration depends on the net force, not on any single force.

Step by step:

1. Vertical forces: A (up, 500 N) and C (down, 500 N) are equal and opposite, so they cancel.
2. Horizontal forces: B (right, 300 N) and D (left, 200 N). Net force = 300 - 200 = 100 N to the right.
3. Newton's second law: a = \dfrac{F_{\text{net}}}{m} = \dfrac{100\ \text{N}}{50\ \text{kg}} = 2\ \text{m/s}^2.

Correct answer: 2 m/s² to the right.

Check: ma = 50 \times 2 = 100 N, which equals the net force ✓

Tip: Before using F = ma, add up the forces in each direction. Forces in opposite directions subtract. Using only the push (300 N) ignores friction and gives an answer that is too large.

A good test changes only one variable (towel or no towel), measures the result (the force needed), and repeats the trials.

Step by step:

1. Independent variable: towel vs. no towel.
2. Dependent variable: force needed to keep the dresser moving at a steady speed. A spring scale (force meter) measures it in newtons.
3. Controlled variables: the same dresser, the same wooden floor, the same steady speed.
4. Repeating each condition three times makes the results more reliable.

Correct answer: pull the dresser at a steady speed with a spring scale across the same floor, with and without the towel, three times each.

Tip: Reject plans that change two things at once (towel and floor), plans with no comparison group, and plans that use opinions instead of measurements.

The table shows that populations with a "Long history of raising animals for milk" (A: 89%, B: 74%) have far more adults with lactase persistence than populations without one (C: 12%, D: 5%).

Natural selection works like this:

1. Variation: some people happened to carry the L allele.
2. Advantage: where milk was available, adults who could digest it got extra food energy and nutrients.
3. Survival and reproduction: those adults were more likely to survive and have more children.
4. Inheritance: their children inherited the L allele, so over many generations the allele became common.

Where milk was not part of the adult diet (C and D), the L allele gave no advantage, so it stayed rare.

Correct answer: in populations that kept milk-producing animals, adults who could digest milk got extra nutrition, so they tended to survive and have more children, passing on the L allele.

Tip: Wrong answers about evolution often say that individuals change because they need to, try to, or use a body part. Natural selection does not create traits on demand; it changes how common existing alleles are.

The calcium chloride line (blue) starts at 22 °C (the passage says the water started "at 22 °C") and reaches its highest value of 38 °C at 3 and 4 minutes. At 5 minutes it has cooled slightly to 37 °C.

Step by step:

1. Starting temperature: 22 °C.
2. Highest temperature: 38 °C.
3. Greatest change: 38 - 22 = 16 °C.

Correct answer: 16 °C.

Why not the others? 38 °C is a temperature reading, not a change. 15 °C uses the 5-minute value (37 °C) instead of the peak. 9 °C is only the change during the first minute (22 → 31 °C).

Tip: "Change" always means a difference between two values. On a line graph, find the start and the extreme value the question asks for, and subtract.

To test whether the amount of ammonium nitrate affects how cold the water gets, the mass of the solid must be the independent variable, and everything else must stay the same as in the original procedure ("10 grams (g) of one solid to 100 milliliters (mL) of water at 22 °C in a foam cup").

Step by step:

1. Change only the mass: 5 g, 10 g, 15 g and 20 g.
2. Keep constant: 100 mL of water, starting temperature 22 °C, the same kind of cup, the same stirring.
3. Measure the dependent variable: the lowest temperature the water reaches.
4. Compare: if larger masses give lower temperatures, more ammonium nitrate makes the water colder.

Correct answer: dissolve 5 g, 10 g, 15 g and 20 g of ammonium nitrate, each in 100 mL of water starting at 22 °C, and record the lowest temperature in each trial.

Tip: First name the independent variable in the question ("more ammonium nitrate" → mass). Then pick the plan that changes only that variable and measures the outcome the question asks about.

Read the seven points (CO₂ in ppm, temperature difference in °C): 1960: 317, −0.03 · 1970: 326, 0.03 · 1980: 339, 0.26 · 1990: 354, 0.45 · 2000: 370, 0.39 · 2010: 390, 0.72 · 2020: 414, 1.01

Step by step:

1. Overall pattern: as CO₂ increases from left to right, the points generally move upward → a positive relationship.
2. Not perfectly steady: 2000 (0.39 °C) was cooler than 1990 (0.45 °C), even though CO₂ was higher.
3. CO₂ did not double: 414 \div 317 \approx 1.31, an increase of about 31%.
4. A scatter plot shows that two variables change together. By itself, it cannot prove that one is the only cause of the other.

Correct answer: years with more carbon dioxide in the atmosphere generally had higher global temperatures, although the pattern was not perfectly steady.

Tip: Words like every, only and prove are red flags in data questions. The best-supported statement describes the overall trend and admits exceptions.

Two explanations are possible for the warming: (1) more greenhouse gases, as the passage describes, or (2) more energy from the Sun.

Step by step:

1. From 1980 to 2020, the plot shows temperature rising from about 0.26 °C to 1.01 °C above the 1951–1980 average.
2. If the Sun caused this, the Sun's energy output should have increased over the same years.
3. The new finding says the Sun's energy "stayed nearly constant" since the late 1970s. A cause that did not change cannot explain a steady rise.
4. So the Sun explanation is weakened. Ruling out a competing explanation makes the passage's greenhouse-gas explanation, which matches rising CO₂ levels, more likely.
5. The finding does not say the Sun has no effect on climate. It only says changes in the Sun do not match this warming.

Correct answer: it weakens the idea that the Sun caused the warming, which makes the greenhouse-gas explanation in the passage more likely.

Tip: When new evidence rules out an alternative explanation, it strengthens the remaining explanation. Be careful not to overstate it: weakening one explanation is not the same as proving another.

Read each activity's Calories per hour from the graph and multiply by the time.

Step by step:

1. Running 30 minutes: 700 \times 0.5 = 350 Calories ✓
2. Bicycling 30 minutes: 500 \times 0.5 = 250 Calories.
3. Cleaning house 1 hour: 250 \times 1 = 250 Calories.
4. Watching TV 4 hours: 80 \times 4 = 320 Calories.

Only running for 30 minutes uses at least 350 Calories.

Correct answer: running at 6 mph for 30 minutes.

Tip: When choices mix different activities and different times, compute each one the same way (rate × time) before comparing. Do not just pick the activity with the biggest bar or the longest time.

The passage says cellular respiration "uses oxygen to break down glucose and other food molecules," that "Carbon dioxide and water are produced as wastes," and that the body uses more energy "when your muscles are active." The graph shows running uses 700 Calories per hour, compared with 80 for watching TV.

Step by step:

1. Running muscles need much more energy (ATP).
2. To make more ATP, muscle cells carry out more cellular respiration in their mitochondria.
3. More respiration uses more oxygen and produces more carbon dioxide.
4. Faster, deeper breathing brings in the extra oxygen and removes the extra carbon dioxide.

Correct answer: running muscle cells carry out more cellular respiration, which uses more oxygen and produces more carbon dioxide that must be removed.

Tip: Connect body systems: the respiratory system (lungs) supplies oxygen and removes carbon dioxide for the cells, but the energy itself is released inside the cells, in the mitochondria.

The passage says the technicians placed disks soaked in antibiotics, and "one disk had been soaked in sterile water." The water disk has everything the other disks have (paper, soaking, the same gel and bacteria) except an antibiotic.

Step by step:

1. In the graph, the water disk has a clear zone of 0 mm for both strains.
2. That shows the paper disk and the liquid alone do not stop bacteria from growing.
3. So when the antibiotic disks show clear zones, the difference can be credited to the antibiotics.

Correct answer: it was a control, showing that a disk without an antibiotic does not stop bacterial growth.

Tip: A control is the comparison condition that does not receive the treatment being tested. On the GED, look for the item labeled "water," "placebo," "no treatment" or "untreated" and ask what it rules out.

Strain 2 "was collected from a patient whose infection did not improve after a week of treatment with antibiotic X," and the graph shows X barely affects it (7 mm vs. 22 mm for Strain 1).

Natural selection in bacteria:

1. Variation: in a huge population of bacteria, a few happen to carry genetic differences (from random mutations) that let them survive antibiotic X.
2. Selection: the antibiotic kills most of the bacteria that lack these differences.
3. Reproduction: the survivors divide and pass their resistance genes to their offspring.
4. Result: after many generations, which can take only days for bacteria, most of the population is resistant.

Correct answer: a few bacteria already had genetic differences that let them survive antibiotic X; they survived the treatment and reproduced, so their resistant offspring became most of the population.

Tip: It is the bacteria that become resistant, not the patient. And the antibiotic does not cause helpful mutations; it selects bacteria that already have them. This is why doctors warn against using antibiotics when they are not needed.

The stem shows that Earth is actually farther from the Sun in July (152 million km) than in January (147 million km). So distance cannot explain why July is summer in the Northern Hemisphere.

The real cause: Earth's tilted axis.

1. Earth's axis is tilted about 23.5°, and the tilt always points the same direction in space.
2. In June and July, the Northern Hemisphere is tilted toward the Sun.
3. Sunlight strikes it more directly (from higher in the sky), so the same energy falls on a smaller area and heats it more.
4. Days are also longer, so there are more hours of heating.
5. Six months later, the Northern Hemisphere is tilted away from the Sun and has winter, while the Southern Hemisphere has summer.

Correct answer: the Northern Hemisphere is tilted toward the Sun, so it gets more direct sunlight and longer days.

Tip: The fact that the two hemispheres have opposite seasons at the same time is strong evidence against the distance explanation: both hemispheres are the same distance from the Sun.