ACT Science Question and Answers

Question 1

A researcher measures the absorbance of three protein solutions at 280 nm and obtains values of 0.42, 0.85, and 1.27 respectively.
If the relationship between concentration and absorbance is linear, what concentration corresponds to an absorbance of 0.85 if the 0.42 value represents 2 mg/mL?

Accepted Answer

4.05 mg/mL

Answer

2.85 mg/mL

Answer

1.70 mg/mL

Answer

6.10 mg/mL

Question 2

In an experiment studying enzyme activity, the reaction rate doubles when temperature increases from 20°C to 30°C but drops sharply at 50°C. Which conclusion is best supported by this data?

Accepted Answer

The enzyme denatures at high temperatures

Answer

The reaction requires more substrate at higher temperatures

Answer

Temperature has no effect on enzyme activity

Answer

The enzyme is most active at 20°C

Question 3

A graph shows the population of two species over 20 years. Species A increases while Species B decreases. Which hypothesis is MOST supported by this data alone?

Accepted Answer

Species A and Species B populations are negatively correlated

Answer

Species A is preying on Species B

Answer

Species B is being outcompeted for food by Species A

Answer

A disease is killing Species B

Question 4

Two experiments test the effect of pH on bacterial growth. Experiment 1 uses a buffer; Experiment 2 does not. Why is Experiment 1 the better experimental design?

Accepted Answer

Buffers maintain stable pH, controlling for metabolic byproducts

Answer

Buffers increase bacterial growth rate

Answer

Buffers eliminate the need for a control group

Answer

Buffers sterilize the growth medium

Question 5

A student measures the mass of a sample before and after heating and records values of 15.62 g and 12.45 g. What percentage of the original mass was lost?

Accepted Answer

20.3%

Answer

25.5%

Answer

17.8%

Answer

15.6%

Question 6

Scientist 1 claims that global temperatures are rising due to increased CO₂. Scientist 2 claims natural solar cycles are responsible. Which evidence would MOST strongly support Scientist 1's view?

Accepted Answer

A strong correlation between CO₂ levels and temperature independent of solar output changes

Answer

Increased solar activity over the past century

Answer

Rising sea levels in coastal cities

Answer

Melting glaciers in mountainous regions