AP Chemistry Chapter I Lesson 3 Significant Numbers

Giving the Cat Bath

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

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

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

Reactant Substances reacting to produce product.

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

Example 2 Na + Cl2  2 NaCl Reactants Product

Accuracy How close is measurement to the true value.

Precision Agreement between several measurements of some quantity.

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

Convert 7 in to cm 17.8 cm

Convert 179 m to cm 1.790 x 104 cm

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

Calculation of significant figures Preceding zeros do NOT count. Ex: 0.00034 is 2 sig #’s Zero between non zero digits count. Ex: 8976.02 is 6 sig #’s

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

Answer Significant # for A. 134.066 B. 100.000 6 sig # 6 sig #

Answer Significant # for: A. 23400 B. 00.009 3 sig # 1 sig #

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.

Rule for significant figures and addition and subtraction. Ex: 12.11 + 18.0 + 1.013 + 31.123 round to nearest tenth due to digit with least precise measurement. So correct answer would be 31.1 due to (18.0).

Mass Amount of matter in an object.

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

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

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 9/5 + 32 = o F Celsius Fahrenheit

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

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