Chapter 2: Scientific Measurement Ms. Campos

Scientific Notation An abbreviation to express extremely large or small numbers.

Adding and Subtracting Step 1: Adjust the powers of 10 in the 2 numbers so that they have the same index. (Tip: It is easier to adjust the smaller index to equal the larger index). Step 2 : Add or subtract the numbers. Step 3 : Give the answer in scientific notation.

Multiplying and Dividing

Let’s Practice! Complete Part A of worksheet

Accuracy vs. Precision It is necessary to make good, reliable measurements in the lab What is accuracy? What is precision? Precision also reflects the number of decimal places in a measurement: ▫ grams is more precise than 2.5 grams

Example Technician A and B measured the density of a substance several time. The actual density is 2.70 g/ml. Which technician was more precise and which was more accurate and why? Tech ATech B g/ml2.5 g/ml g/ml2.9 g/ml g/ml2.7 g/ml

Significant Figures What are significant figures? Measurement that includes all of the digits that are know plus one more digit that is estimated. Measurements must be reported to the correct number of sig figs.

Rules for Counting Sig Figs 1.Non-zero numbers always count as sig figs: 3456 has ____ sig figs 2.Leading zeroes do not count as sig figs: has ____ sig figs 3.Captive zeroes always count as sig figs: has ___ sig figs 4.Trailing zeros are significant only if the number contains a written decimal point: has ____ sig figs 100 has ____ sig fig 100. has ____ sig figs

Let’s Practice Complete Part B of handout

Rules for Sig Figs in Mathematical Operations Addition and Subtraction: The number of decimal places in the result equals the number of decimal places in the least precise measurement

Rules for Sig Figs in Mathematical Operations Multiplication and Division: number of sig figs in the result equals the number in the least precise measurement used in the calculation.

Let’s Practice Complete Part C of worksheet