Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Unit 1: Ch. 1 & 3 Intro to Chemistry & Scientific Measurements

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. “DO NOW”: What is wrong with an advertisement for juice drinks that claims the juice is all-natural and free of chemicals?

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Section 1.1 Chemistry is the study of the composition of matter and the changes that matter undergoes. Five traditional areas of study are: organic chemistry inorganic chemistry biochemistry analytical chemistry physical chemistry

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. e.g., trees, water, and buildings, etc. Matter is anything that has mass and occupies space.

Section 1.2 Chemistry can be useful in explaining the natural world, 2. preparing people for career opportunities, 3. producing informed citizens Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Section 1.3 Scientific method - a logical, systematic approach to the solution of a scientific problem Making observations (use your senses to obtain info) Testing hypotheses (proposed explanations for an observation) with experiments Independent variable – (manipulated) – variable you can change during an experiment Dependent variable – (responding) – variable that is observed during an experiment Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Developing theories (well-tested explanations for a broad set of observations) Scientific laws (summarizes results of many observations and experiments) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Experiments Theory Hypothesis Observations Scientific Law Please copy diagram into notes.

Section 1.4 Problem Solving In Science “5-Step Problem Solving” 1. Write down any “knowns” and “unknowns”. 2. Write the appropriate equation. 3. Plug in actual measurements (both numbers and units) into the equation. 4. Solve numbers. Check for Sig Figs. 5. Solve units and box/circle answer. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

EXAMPLE A rock has a mass of 3.0 grams and a volume of 1.5 cubic centimeters. What is the density of the rock? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Section 3.1 Measurement - a quantity that has both a number and a unit e.g., 66 inches, 37 o C Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How do you write a number in Scientific Notation? Scientific notation - a given number is written as the product of two numbers: a coefficient and 10 raised to a power e.g., 602,000,000,000,000,000,000, x coefficient is always a number > 1 and < 10. exponent is an integer Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

When writing numbers greater than ten in scientific notation, the exponent is positive and equals the number of places that the original decimal point has been moved to the left. 6,300,000. = 6.3 x ,700. = 9.47 x 10 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Numbers less than one have a negative exponent when written in scientific notation. The value of the exponent equals the number of places the decimal has been moved to the right = 8 x 10 – = 7.36 x 10 –3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Accuracy & Precision How do you evaluate accuracy & precision? Accuracy, precision, and error help determine the reliability of measurements. The accuracy of a measurement is determined by how close the measured value is to the actual value. The precision of a measurement is determined by how close repeated measurements are to one another. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Which of the following are examples of accuracy and/or precision?

Determining Error  Error is the difference between the measured value and the accepted value accepted value - the correct value for the measurement based on reliable references experimental value - the value measured in the lab. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Error = experimental value – accepted value Percent error =  error  accepted value 100% x

EXAMPLE The boiling point of pure water is measured to be 99.1°C. Calculate the percent error. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Experimental value = 99.1°C Accepted value = 100.0°C Percent error = ? accepted value x 100%Percent error = |error | ____________ _______ = 100.0°C X 100 % = 0.9% 0.9°C|99.1°C – 100.0°C| X 100%= 100.0°C