Scientific Method
What are the six general steps of the scientific method?
Observation, Question, Hypothesis, Experiment, Data Collection, Conclusion
Which axis does the independent variable go on in a graph?
X-axis (horizontal)
Name the three measures of central tendency.
Mean, Median, Mode
What elements make up nearly all living matter?
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur
What type of bond holds hydrogen to oxygen within a water molecule?
Polar covalent bond
What is the difference between a hypothesis and a prediction?
Hypothesis is an explanation for an observation; a prediction is a specific outcome expected if the hypothesis is correct
Constants vs. controls — how are they different?
Constants are kept the same in all groups; controls are specific groups used for comparison
Which measure of center is best for skewed data sets?
Median (less affected by outliers)
Why does water have a high specific heat capacity?
Hydrogen bonds absorb heat, requiring more energy to change temperature
What type of bond forms between two water molecules?
Hydrogen bond
Why is it important to include a null hypothesis?
It provides a baseline for comparison and allows statistical testing against “no effect”
When should you use a positive control? A negative control?
Positive: shows expected effect; Negative: ensures no effect when there should be none
What does standard deviation measure?
The average distance of values from the mean (spread of data)
Give an example of how water’s high heat of vaporization benefits organisms.
Evaporative cooling helps regulate body temperature (ex: sweating)
How does electronegativity affect hydrogen bonding?
The difference in electronegativity between O and H makes water polar, allowing hydrogen bonds to form
If standard error bars overlap, what does this mean?
There is no statistically significant difference between the groups
In an experiment testing a new antibiotic against S. pyogenes, what would be a good positive control?
Treatment with penicillin
How does increasing sample size affect standard error?
Larger sample size decreases standard error
Define cohesion and adhesion. Provide one example of each.
Cohesion = water sticking to itself (surface tension); Adhesion = water sticking to other surfaces (capillary action in plants)
How do hydrogen bonds give rise to surface tension?
Cohesion of water molecules at the surface creates a "film-like" tension
Why do scientists use statistical tests?
To determine if observed differences are due to chance or a real effect
Why must only one independent variable be changed?
To ensure the dependent variable changes are due only to the manipulated variable
What does it mean if 95% confidence intervals do not overlap?
The difference between means is statistically significant
What would happen if O and H had the same electronegativity?
Water would lose polarity, no hydrogen bonds, and properties like cohesion, adhesion, and temperature regulation would be lost
Why are hydrogen bonds weaker than covalent bonds, yet biologically important?
Individually weak but collectively strong; allow flexibility in DNA, proteins, and water’s properties