1. AP Chemistry Chapter I Lesson 3
Significant Numbers

2. Giving the Cat Bath

3. Question
A sample of carbon dioxide that undergoes a transformation from solid to liquid to gas would undergo
(A) a change in mass (B) a change in density (C) a change in composition (D) no change in physical properties
Answer B

4. Question A solution is a(n)
(A) compound (B) pure substance (C) homogeneous mixture of substances (D) heterogeneous mixture of substances
Answer C

5. Chemical Equation
Symbolic representation of the change or changes occurring.
sodium bicarbonate + hydrochloric acid
Sodium chloride + water + carbon dioxide     

6. Reactant
Substances reacting to produce product.

7. Product
Substances that are produced.
iron + oxygen Iron III oxide     

8. Example
2 Na + Cl2  2 NaCl
Reactants Product

9. Accuracy
How close is measurement to the true value.

10. Precision
Agreement between several measurements of some quantity.

11. Ions electrically charged atoms or groups of atoms. Cations (+)
charged ions
Anion (-) charged ions

12. Convert
7 in to cm
17.8 cm

13. Convert
179 m to cm
1.790 x 104 cm

14. Convert
15 km/L to mi/gal
35 mi /gal

15. Calculation of significant figures
Preceding zeros do NOT count.
Ex: is 2 sig #’s
Zero between non zero digits count.
Ex: is 6 sig #’s

16. Calculation of significant figures cont.
Trailing zeros do NOT count.
Ex: 100 is 1 sig #
Zeros behind the decimal after a non zero digit DO count.
Ex: 1.00 x 102 is 3 sig #’s

17. Answer
Significant # for A B
6 sig #
6 sig #

18. Answer
Significant # for: A B
3 sig #
1 sig #

19. Rules for Significant figures in multiplying and dividing.
Ex: 4.56 x 1.4 = 6.38 round to 6.4 use the number that has the least number of significant figures.
Due to the least precise number.

20. Rule for significant figures and addition and subtraction.
Ex: round to nearest tenth due to digit with least precise measurement.
So correct answer would be 31.1 due to (18.0).

21. Mass
Amount of matter in an object.

22. Volume
1 L = 1000ml = 1000 cm3 = 1 dm3

23. Temperature
property of matter that determines whether heat energy can be transferred from one body to another and the direction of that transfer.

24. Formulas: a. Convert oF to o C (o F - 32) x 5/9 = o C
b. Convert o C to o F o C x 9/ = o F
Celsius
Fahrenheit

25. Formulas: c. Convert o C to K o C + 273.15 = K or K - 273.15 = o C
Lord Kelvin

26. Absolute Zero
lowest possible temperature. Where all motion of molecules ceases.