SI Units, Conversions, Accuracy, Precision, and Significant Figures

Flashcards covering SI base units, temperature and prefix conversions, the concepts of accuracy versus precision, and rules for calculations involving significant figures.

What is the SI unit for length?

Meter ($\text{m}$)

What is the SI unit for mass?

Kilogram ($\text{kg}$)

What is the SI unit for time?

Second ($\text{s}$)

What is the SI unit for temperature?

Kelvin ($\text{K}$)

What unit would you use to measure the length of a table?

Meters ($\text{m}$) or centimeters ($\text{cm}$)

What unit would you use to measure the mass of a chemical?

Grams ($\text{g}$) or kilograms ($\text{kg}$)

What is $25^\circ\text{C}$ converted to Kelvin?

$$298\,\text{K}$$

What is $300\,\text{K}$ converted to $^\circ\text{C}$?

$$27^\circ\text{C}$$

What is $68^\circ\text{F}$ converted to $^\circ\text{C}$?

$$20^\circ\text{C}$$

What is $0^\circ\text{C}$ converted to $^\circ\text{F}$?

$$32^\circ\text{F}$$

What is $100^\circ\text{C}$ converted to $^\circ\text{F}$?

$$212^\circ\text{F}$$

What is $32^\circ\text{F}$ converted to $^\circ\text{C}$?

$$0^\circ\text{C}$$

Which temperature scale starts at absolute zero?

Kelvin

What does the prefix kilo- mean?

$$10^3 = 1{,}000$$

What does the prefix centi- mean?

$$10^{-2} = 0.01$$

What does the prefix milli- mean?

$$10^{-3} = 0.001$$

What does the prefix micro- mean?

$$10^{-6} = 0.000001$$

What is $5.0\,\text{km}$ converted to meters?

$$5{,}000\,\text{m}$$

What is $2500\,\text{mg}$ converted to grams?

$$2.5\,\text{g}$$

What is $3.5\,\text{L}$ converted to mL?

$$3{,}500\,\text{mL}$$

What is $450\,\text{cm}$ converted to meters?

$$4.50\,\text{m}$$

What is $0.025\,\text{kg}$ converted to grams?

$$25\,\text{g}$$

Why is it important to include a unit with a measurement?

Units tell us what the number represents.

What is wrong with saying, "The mass is 25" instead of "The mass is 25 g"?

We don't know what unit is being used.

If someone says a table is 5 long, what information is missing?

The unit, such as meters or centimeters.

Can the number 10 represent different measurements depending on the unit?

Yes. $10\,\text{m}$ is very different from $10\,\text{cm}$.

What does accuracy mean?

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

What does precision mean?

How close measurements are to each other.

Which concept means being close to the true value?

Accuracy

Which concept means getting measurements close to each other?

Precision

Can measurements be precise but not accurate?

Yes

Can measurements be accurate but not very precise?

Yes

If an accepted value is $10.0\,\text{g}$, how are measurements of $10.0\,\text{g}$, $10.1\,\text{g}$, and $9.9\,\text{g}$ categorized?

Accurate AND precise (they are close to $10.0\,\text{g}$ and close to each other).

If an accepted value is $10.0\,\text{g}$, how are measurements of $15.0\,\text{g}$, $15.1\,\text{g}$, and $15.0\,\text{g}$ categorized?

Precise but NOT accurate (they are close to each other but far from $10.0\,\text{g}$).

If an accepted value is $10.0\,\text{g}$, how are measurements of $8.0\,\text{g}$, $12.0\,\text{g}$, and $10.0\,\text{g}$ categorized?

Accurate but NOT precise (they are spread out, but the average is around the accepted value).

If an accepted value is $10.0\,\text{g}$, how are measurements of $14.2\,\text{g}$, $14.3\,\text{g}$, and $14.2\,\text{g}$ categorized?

Precise but NOT accurate (they are very close to each other but far from $10.0\,\text{g}$).

How many significant figures are in $45.6$?

3

How many significant figures are in $0.0045$?

2

How many significant figures are in $100.0$?

4

How many significant figures are in $500$ (assuming no decimal point)?

1

How many significant figures are in $5.020$?

4

How many significant figures are in $0.05060$?

4

Which zeros count as significant figures?

Zeros between nonzero numbers and zeros at the end of a decimal number count.

Do leading zeros count as significant figures?

No. Example: $0.0045$ has only 2 significant figures.

What is $12.5 + 3.2$ using significant figures rules?

$$15.7$$

What is $15.67 - 2.1$ using significant figures rules?

$$13.6$$

What is $4.5 \times 2.0$ using significant figures rules?

$9.0$ (2 significant figures)

What is $10.00 \div 2.5$ using significant figures rules?

$4.0$ (2 significant figures)

What is $25.0 + 3.45 + 1.2$ using significant figures rules?

$29.7$ (One decimal place)

What is $6.02 \times 3.1$ using significant figures rules?

$19$ (2 significant figures)