2-3 How do chemists measure quantities?
Concept Review
Measuring and Calculating
1. What is the difference between accuracy and precision? _____________________________________________________________________________
________________________________________ _____________________________________
2. Suppose a chemistry student took the mass of a sample of Calcium Carbonate and obtained the following values: 1.01g, 1.00g, 0.99g, and 0.98g. The known mass was 1.00g. Was this measurement accurate of precise? _____________________________________________________________________________
Significant Figures
3. Determine the number of significant figures n the following. (HINT: see how to on page 62)
a. 4 001.006g___
b. 3 cars___
c. 0.000 0456g___
d. 1 001.000 000g___
e. 100g___
f. 10.000 004 56g___
g. 2 000 000g___
h. 2 000 000.g___
i. 2 000 000.000g___
j. 20 students___
4. Explain why some numerical values have an unlimited number of significant digits. _____________________________________________________________________________
_______________________________________ ______________________________________
5. Perform the following operations. Express you answer with the correct number of significant figures.
a. 37.26m + 2.7m + 0.0015m = ____
b. 256.3mL + 2L + 137mL + 10L = ____
c. _____
d. _____
6. Why should you round only at the final answer when performing a sequence of calculations? ___________________________________________________________________________
___________________________________________ ________________________________
Scientific Notation
7. Convert the following to scientific notation.
a. 0.000 003 6mm _____________
b. 1 450 000mg _______________
c. 2340m____________________
d. 111.34g/cm3________________
8. Perform the following calculations. Express your answers in scientific notation.
a. 4.5 x 10^6 + 3.9 x 10 8 = ______________
b. (3.9 x 10 3)(6.7 x 10 2) =_______________
c. ___________________________
d. 5.6 x 10 7 – 2.3 x 10 6 = ________________
e. 6.7 x 10 12 + 7.8 x 10 12 = ______________
f. 3.7 x 10 12 – 2.1 x 10 12 = ______________
g. (6.02 x 10 23)(2.00) = _________________
h. __________________________
Practice Problems
9. Three chemistry students measured the length of a copper bar. The recorded lengths were 5.05cm, 5cm, and 5.1cm. What is the average length of the bar?
Answer: _________