PPT2 Test Review - Bennett

HN Chemistry PVI

What is a measurement?

A measurement compares an object with a standard unit and contains some degree of error.

What are the three parts of every measurement?

Unit, magnitude, and uncertainty.

What is the unit in a measurement?

What is being measured, such as grams, feet, or liters.

What is magnitude in a measurement?

The numerical value, such as 4.27 ft or 3.8 g.

What is uncertainty in a measurement?

The estimated part of the measurement.

What is an example of a length measurement?

5 meters, 10.3 miles, or 2 inches.

What is an example of a speed measurement?

55 miles/hour or 75 km/hour.

What is an example of a mass measurement?

72 kg, 55 pounds, or 77.46 grams.

How are units treated in calculations?

Units are treated like algebraic variables.

What is the rule for addition and subtraction of units?

They require the same units.

What is the rule for multiplication and division of units?

They can use different units.

What are significant figures?

Digits known with certainty plus one estimated digit.

How do you determine significant figures when a decimal is present?

Count from the left side toward the first nonzero digit.

How do you determine significant figures when a decimal is absent?

Count from the right side toward the first nonzero digit.

What is the rule for multiplication and division regarding significant figures?

The answer must have the same number of significant figures as the measurement with the fewest significant figures.

What is the rule for addition and subtraction regarding significant figures?

The answer must have the same number of decimal places as the least precise measurement.

What is the rounding rule if the dropped digit is greater than 5?

Round up.

What is the rounding rule if the dropped digit is less than 5?

Do not change the previous digit.

What is accuracy in measurements?

How close a measurement is to the true or accepted value.

What is precision in measurements?

How reproducible a group of measurements is.

What is percent error?

The difference between the observed value and the true value, expressed as a percentage.

What is the observed value?

The value obtained from performing an experiment.

What is the true value?

The actual or theoretical value found in literature.

What is the International System of Units (SI)?

The modern form of the metric system developed in 1960.

What is an ampere?

The unit that measures the amount of electric charge passing a point in a circuit per second.

What is a terameter?

A unit of length equal to 10^12 meters.

What does the SI mnemonic represent?

The order of SI prefixes from tera to pico.

What is the rule for arithmetic operations with units?

Quantities must have the same units for addition and subtraction.

What is a conversion factor?

A ratio that represents equality between two units.

How do conversion factors affect measurements?

They do not change the value of a measurement.

What is dimensional analysis?

A method using conversion factors and unit-labeled numbers to solve problems.

What is the first step in solving a conversion problem?

Identify the unknown, including its units.

What should you do after identifying the unknown in a conversion problem?

Choose a starting point.

What is the purpose of listing needed conversion factors?

To multiply the starting measurement by them.

What should you do to the units in dimensional analysis?

Cancel unwanted units until the correct ending unit remains.

What is the equation used for heat calculations?

Q = mcΔT.

What does 'm' represent in the heat calculation equation?

The mass of the substance, measured in grams.

What does 'c' represent in the heat calculation equation?

The specific heat of the substance.

What does 'ΔT' represent in the heat calculation equation?

The change in temperature.

What is significant figures?

All digits known with certainty plus one estimated or uncertain digit.

What controls the number of digits reported in a calculated answer?

Significant figures.

What is the Pacific-side rule for counting significant figures?

Start on the left, move to the first nonzero digit, and count that digit and everything to the right.

What is the Atlantic-side rule for counting significant figures?

Start on the right, move to the first nonzero digit, and count that digit and everything to the left.

How many significant figures are in 36.600?

Five significant figures.

How many significant figures are in 36,600?

Three significant figures.

What is the multiplication and division significant-figure rule?

The answer must have the same number of significant figures as the original value with the fewest significant figures.

What is the addition and subtraction significant-figure rule?

The answer must have the same number of decimal places as the least precise number in the calculation.

What is the answer to 36 cm × 1.03 cm?

37 cm².

What is the answer to 12.11 + 18.0 + 1.013?

31.1.

What are the three parts of a measurement?

Unit, magnitude, and uncertainty.

Why are measurements inexact?

They always contain some degree of error.

How are counted numbers different from measurements?

Counted numbers are exact, while measurements are inexact.

How are units used in algebra?

Units can be added, subtracted, multiplied, divided, and canceled like algebraic variables.

What is an uncertain digit?

The final digit of a measurement; it is estimated.

What must you consider when counting significant figures?

Nonzero digits, leading zeros, trailing zeros, placeholder zeros, and whether a decimal is present.

What is the method for heat calculations?

Write the equation, solve for the unknown, substitute numbers and units, and calculate the answer.

What does it mean if measurements are accurate and precise?

Measurements are close to the accepted value and close to each other.

What does it mean if measurements are accurate but not precise?

Measurements are close to the accepted value but spread apart from one another.

What does it mean if measurements are precise but not accurate?

Measurements are close to one another but far from the accepted value.

What does it mean if measurements are neither accurate nor precise?

Measurements are far from the accepted value and far from one another.

What affects accuracy and precision?

The circumstances and the type of instruments used to make measurements.

What is the formula for absolute error?

Absolute error = observed value minus true value.

Can absolute error be negative?

Yes, absolute error may be positive or negative.

What does a negative percent error indicate?

The observed value is below the standard value.

What percent error should almost always be achievable?

Less than 10%.

What is the SI system?

The International System of Units, which is the modern form of the metric system.

When was the SI system developed?

1960.

What is the purpose of the SI system?

To create a common set of units from which other measurements can be derived.

What is the SI base unit for length?

Meter, m.

What is the SI base unit for mass?

Kilogram, kg.

What is the SI base unit for time?

Second, s or sec.

What is the SI base unit for temperature?

Kelvin, K.

What is the SI base unit for amount of substance?

Mole, mol.

What is the SI base unit for electric current?

Ampere, A.

What is the SI base unit for luminous intensity?

Candela, cd.

What is the SI derived unit for area?

Square meter, m².

What is the SI derived unit for volume?

Cubic meter, m³.

What is the SI derived unit for velocity?

Meter per second, m/s.

What is the SI derived unit for acceleration?

Meter per second squared, m/s².

What is the SI derived unit for density?

Grams per cubic centimeter, g/cm³.

What is the SI derived unit for energy?

Joule, J.

What is the SI derived unit for pressure?

Pascal, Pa.

What does the SI-prefix mnemonic represent?

Tera, giga, mega, kilo, hecto, deca, base unit, deci, centi, milli, micro, nano, and pico.

What is the main goal of dimensional analysis?

Cancel all unwanted units so that only the desired unit remains.

What is the first step in a conversion problem?

Identify the unknown and its units.

What is the last step in a conversion problem?

Check whether the answer makes sense.

What should you do if the temperature is given in Fahrenheit?

Convert it to Celsius before using the specific-heat equation when the specific heat is given in joules per gram-degree Celsius.