Chem 101L: Chemistry Bootcamp

What is a hypothesis?

A tentative, testable explanation for an observation.

Can hypotheses be proven?

No — they can only be supported or disproven.

What makes a hypothesis testable?

It must make predictions that can be evaluated by experiment.

What are qualitative observations?

Observations made without numbers (color, odor, texture, sound).

What are quantitative observations?

Observations involving numerical measurements.

Why are observations important in chemistry?

They reveal physical or chemical changes occurring in a system.

What do significant figures represent?

All certain digits + one estimated digit.

How do you determine sig figs in analog measurements?

Read to one digit beyond the smallest marking (estimate last digit).

Do digital instruments require an estimated digit?

No — all digits are significant.

How are sig figs handled in multiplication/division?

Result has same number of sig figs as value with the fewest sig figs.

How are sig figs handled in addition/subtraction?

Result has same number of decimal places as the value with the fewest decimal places.

Formula for density?

Density = Mass / Volume.

Units of density for liquids?

g/mL or g/cm³.

How does temperature affect density?

Density decreases as temperature increases because volume expands.

Why is density an intensive property?

It does not depend on the amount of substance.

What is accuracy?

How close a measurement is to the true value.

What is precision?

How closely repeated measurements agree with each other.

What is random error?

Error due to uncertainty or limitations in measuring tools; affects precision.

What is systematic error?

Consistent, directional error caused by faulty calibration or technique; affects accuracy.

Formula for the mean?

Mean = (Sum of values) / (Number of values).

What does standard deviation measure?

The spread of data around the mean; lower SD = higher precision.

Formula for standard deviation (conceptually)?

Square root of the average squared deviation from the mean.

What is the coefficient of variation (CV)?

(Standard deviation ÷ Mean) × 100%.

What does the coefficient of variation represent?

Precision relative to the mean; useful for comparing data sets

When do you use percent difference?

To compare two experimental values when no true value is known.

Formula for percent difference?

|x – y| / x × 100%, where x = higher quality value.

When do you use percent error?

When there is a known true or accepted value.

Formula for percent error?

|true – measured| / true × 100%.

What is calibration?

Comparing an instrument's reading to a standard to ensure accuracy.

What is a standard?

A substance with a known, accurate true value.

Why is calibration important?

To eliminate systematic error.

What is a Newtonian fluid?

A fluid whose viscosity does not change with applied force.

What is a non-Newtonian fluid?

A fluid whose viscosity changes depending on stress (e.g., shear-thickening or thinning).

What is a chemical change?

A change where new substances with new properties form.

What is a physical change?

A change that does not alter chemical identity (state changes, dissolving, breaking).

Signs of chemical change?

Gas formation, color change, temperature change, precipitate formation, odor change.

What is a beaker used for?

Holding, mixing, or heating substances; not for accurate measuring.

What is a graduated cylinder used for?

Moderately precise volume measurements.

What is a buret used for?

Highly precise measurement and delivery of liquid volumes.

What is a volumetric flask used for?

Preparing solutions of exact volume and concentration.

What are micropipettes used for?

Delivering microliter volumes with high precision.

Why must balances be tared?

To zero out the container mass and measure only the added substance.

What is the correct method for smelling chemicals?

Wafting — gently fanning vapors toward your nose.

Should you taste chemicals in the lab?

Never.

hy must you read glassware at eye level?

To avoid parallax error.