GED Science Preparation Course：Science practices: experiments, data and evidence

1. 第1题，共16题

   What is the independent variable in Maya's experiment?

   Maya wants to know whether water temperature changes how fast sugar dissolves. She fills four cups with 200 mL of water each, at 10°C, 25°C, 40°C and 60°C. She drops one 5 g sugar cube into each cup, stirs each cup the same way, and times how long the sugar takes to disappear.

   Results: 10°C: 95 seconds; 25°C: 70 seconds; 40°C: 48 seconds; 60°C: 30 seconds.

   • AThe time for the sugar to dissolve
   • BThe amount of water in each cup
   • CThe water temperature
   • DThe mass of the sugar cube
   显示答案

   答案: C. The water temperature

   The independent variable is what the scientist changes on purpose. Maya chose four different temperatures.

2. 第2题，共16题

   What is the dependent variable in Maya's experiment?

   Maya wants to know whether water temperature changes how fast sugar dissolves. She fills four cups with 200 mL of water each, at 10°C, 25°C, 40°C and 60°C. She drops one 5 g sugar cube into each cup, stirs each cup the same way, and times how long the sugar takes to disappear.

   Results: 10°C: 95 seconds; 25°C: 70 seconds; 40°C: 48 seconds; 60°C: 30 seconds.

   • AThe volume of water in each cup
   • BThe way she stirs each cup of water
   • CThe time for the sugar to dissolve
   • DThe water temperature in each cup
   显示答案

   答案: C. The time for the sugar to dissolve

   The dependent variable is what is measured. Maya timed how long the sugar took to disappear.

3. 第3题，共16题

   Which is a controlled variable in Maya's experiment?

   Maya wants to know whether water temperature changes how fast sugar dissolves. She fills four cups with 200 mL of water each, at 10°C, 25°C, 40°C and 60°C. She drops one 5 g sugar cube into each cup, stirs each cup the same way, and times how long the sugar takes to disappear.

   Results: 10°C: 95 seconds; 25°C: 70 seconds; 40°C: 48 seconds; 60°C: 30 seconds.

   • AThe time for the sugar to dissolve
   • BThe result at 60°C
   • CThe volume of water in each cup
   • DThe water temperature
   显示答案

   答案: C. The volume of water in each cup

   Controlled variables are kept the same. Every cup had 200 mL of water, so only temperature changed.

4. 第4题，共16题

   Which conclusion is best supported by Maya's results?

   Maya wants to know whether water temperature changes how fast sugar dissolves. She fills four cups with 200 mL of water each, at 10°C, 25°C, 40°C and 60°C. She drops one 5 g sugar cube into each cup, stirs each cup the same way, and times how long the sugar takes to disappear.

   Results: 10°C: 95 seconds; 25°C: 70 seconds; 40°C: 48 seconds; 60°C: 30 seconds.

   • AStirring has no effect on how fast sugar dissolves
   • BSalt dissolves faster than sugar in warm water
   • CSugar cannot dissolve at all in water that is colder than 10°C
   • DWithin this range, sugar dissolved faster in warmer water
   显示答案

   答案: D. Within this range, sugar dissolved faster in warmer water

   The time fell from 95 s to 30 s as the temperature rose. The data say nothing about salt, stirring or temperatures below 10°C.

5. 第5题，共16题

   How could Maya make her results more reliable?

   Maya wants to know whether water temperature changes how fast sugar dissolves. She fills four cups with 200 mL of water each, at 10°C, 25°C, 40°C and 60°C. She drops one 5 g sugar cube into each cup, stirs each cup the same way, and times how long the sugar takes to disappear.

   Results: 10°C: 95 seconds; 25°C: 70 seconds; 40°C: 48 seconds; 60°C: 30 seconds.

   • ATest only the 60°C cup again with a new cube
   • BStop timing before the sugar fully dissolves
   • CUse a different amount of sugar in each of the cups
   • DRepeat each temperature and average the results
   显示答案

   答案: D. Repeat each temperature and average the results

   Repeated trials reduce random error. Changing the sugar amount would add a second variable.

6. 第6题，共16题

   Which statement is a testable hypothesis?

   • APlants were probably happier in the past
   • BIf plants get more light, then they will grow taller
   • CSome people like plants more than animals
   • DPlants are the most beautiful living things on Earth
   显示答案

   答案: B. If plants get more light, then they will grow taller

   A hypothesis is a prediction that can be tested by measuring something, often written as "If …, then …."

7. 第7题，共16题

   In a medicine study, one group gets the new medicine and another group gets a pill with no medicine. Why is the second group used?

   • AIt makes the study finish faster and cost less money
   • BIt removes the need to measure any results
   • CIt gives a baseline to compare the results with
   • DIt is the independent variable of the study
   显示答案

   答案: C. It gives a baseline to compare the results with

   A control group gets no treatment, so scientists can see whether the medicine made a difference.

8. 第8题，共16题

   Which is an inference rather than an observation?

   • AThe soil feels dry and crumbly when you touch it
   • BThe plant's leaves are yellow with brown edges
   • CThe plant is 24 cm tall when measured with a metric ruler
   • DThe leaves are yellow, so the plant may need water
   显示答案

   答案: D. The leaves are yellow, so the plant may need water

   An observation is what you notice directly. An inference is an explanation based on observations.

9. 第9题，共16题

   What is a scientific theory?

   • AAn opinion shared by most people
   • BA well-tested explanation backed by much evidence
   • CA single experiment's result
   • DA guess that a scientist makes before doing any research
   显示答案

   答案: B. A well-tested explanation backed by much evidence

   In science, a theory is not just a guess; it is supported by much evidence and testing.

10. 第10题，共16题

    Use the table. What is the best prediction of plant height with 10 hours of light per day?

    Hours of light per day	Average plant height (cm)
    4	6
    8	11
    12	16
    16	21

    • A27 cm
    • B16 cm
    • C13.5 cm
    • D11 cm
    显示答案

    答案: C. 13.5 cm

    Height rises 5 cm for every 4 more hours of light. 10 hours is halfway between 8 and 12 hours, so the height is about halfway between 11 and 16 cm: 13.5 cm.

11. 第11题，共16题

    Four trials of an experiment gave these results: 10, 14, 11 and 17 seconds. What is the mean?

    • A12.5 seconds
    • B17.3 seconds
    • C7 seconds
    • D13 seconds
    显示答案

    答案: D. 13 seconds

    Mean = (10 + 14 + 11 + 17) ÷ 4 = 52 ÷ 4 = 13 seconds. 12.5 is the median and 7 is the range.

12. 第12题，共16题

    Daily high temperatures for five days were 18, 22, 25, 19 and 21°C. What is the range?

    • A21°C
    • B7°C
    • C25°C
    • D4°C
    显示答案

    答案: B. 7°C

    Range = largest − smallest = 25 − 18 = 7°C. 21°C is the mean.

13. 第13题，共16题

    Seven students counted the insects in their yards: 3, 8, 5, 9, 5, 2 and 7. What is the median?

    • A7
    • B39
    • C5
    • D9
    显示答案

    答案: C. 5

    In order: 2, 3, 5, 5, 7, 8, 9. The middle (4th) value is 5.

14. 第14题，共16题

    A bag holds 4 green beads and 6 yellow beads. You pick one without looking. What is the probability it is green?

    • A1/4 (25%)
    • B4/6 (about 67%)
    • C2/5 (40%)
    • D3/5 (60%)
    显示答案

    答案: C. 2/5 (40%)

    Probability = wanted outcomes ÷ total outcomes = 4 ÷ 10 = 2/5, or 40%. 4/6 compares green to yellow instead of to the total.

15. 第15题，共16题

    A recipe for a lab solution needs 2.5 L of water. How many milliliters is that?

    • A2,500 mL
    • B250 mL
    • C25,000 mL
    • D25 mL
    显示答案

    答案: A. 2,500 mL

    Milli- means one thousandth, so 1 L = 1,000 mL. 2.5 × 1,000 = 2,500 mL.

16. 第16题，共16题

    The table shows that ice cream sales and sunburn cases rise and fall together. What is the best explanation?

    Month	Ice cream sales	Sunburn cases at a clinic
    April	1,200	8
    June	3,900	31
    August	4,300	35
    October	1,100	6

    • AThe clinic must have copied the numbers wrong
    • BEating ice cream causes people to get sunburned
    • CGetting a sunburn makes people want to buy more ice cream to cool down
    • DA third factor, such as sunny weather, likely causes both
    显示答案

    答案: D. A third factor, such as sunny weather, likely causes both

    Correlation is not causation. Two things can rise together because a third factor, here sunny weather, affects both.

键盘：按1–4作答，按 Enter 进入下一题。

真实考试：145 on a 100–200 scale