Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA Introductory Chemistry, 3 rd Edition Nivaldo Tro 2009, Prentice Hall Chapter 1 The Chemical World

Tro's "Introductory Chemistry", Chapter 1 2 What Is Chemistry? Observation: is sand different than water Test the similarities and differences between sand and water. Composition  Types & number of atoms, structure, Properties  Chemical: how hot, how fast  Physical: size, ability to loose/gain electrons

3 Structure Determines Properties Everything is made of tiny particles called atoms and molecules. Chemists study these particles, looking at the kinds, numbers, structure, size which produce varying chemical and physical properties.

4 The Scientific Method Humans are by nature curious. Have you ever heard a 3 year old repeatedly ask “why?” Science is just exploring nature. A scientists is just a person exploring. You begin to organize your thoughts into Observation, you group those observations into Hypotheses, using Experimentation, and formulate Laws or Theories.

Tro's "Introductory Chemistry", Chapter 1 5 Why Aren’t the Philosophers Considered Scientists Philosophers: Observe nature. Explain the behavior of nature. Communicate and debate ideas with other philosophers. Truth is revealed through logic and debate. Scientists: Observe nature. Explain the behavior of nature. Communicate and debate ideas with other scientists. Truth is revealed through experimentation.

Tro's "Introductory Chemistry", Chapter 1 6 Observation Acquiring information or data Some observations are simple descriptions “The soda pop is a liquid with a brown color and a sweet taste. Bubbles are seen floating up through it.” Some observations compare a characteristic. “A 240-mL serving of soda pop contains 27 g of sugar.”

Tro's "Introductory Chemistry", Chapter 1 7 Hypothesis Looking at your observations you come up with: The sweetness of soda pop is due to the presence of  Sugar or  Aluminum

Tro's "Introductory Chemistry", Chapter 1 8 Experiments Test your hypotheses with a taste test: sugar and aluminum. Theory Sugar is sweet

Tro's "Introductory Chemistry", Chapter 1 9 Laws Typically a fact of nature, often a math constant/number and unit. Law of Conservation of Mass— “In a chemical reaction matter is neither created nor destroyed.” Speed of Light, E = mc 2, Dalton’s Gas Law, Universal Gas Constant, etc… Unlike California State laws, you cannot choose to violate a scientific law

Tro's "Introductory Chemistry", Chapter 1 10 Theories Explains how nature behaves. Newton’s Gravitational Theory: how an apple falls Dalton’s Atomic Theory: atoms look like… Darwin’s Theory of Evolution: we always change Einstein's Theory of Relativity: light is constant Used to predict future observations.

Tro's "Introductory Chemistry", Chapter 1 11 What’s the Difference Between a Law and a Theory? Laws: Very specific, “What will happen” often expressed in mathematical equations. Theories: Very general, “Why it will happen,” often includes many “Laws”

Tro's "Introductory Chemistry", Chapter 1 12 Do we need science? A history lesson in science A key feature of science are it’s experiments Experiments must be duplicated by other’s!!! Galileo ( ) and Newton ( ) worked on physics, the first Scientists Lavoisier is first to use the scientific method on objects/nature on things that could not be “Seen”

13 What causes Burning? Phlogiston Theory The mid-1700s theory of how wood or coal burned, referred to as combustion. Wood and coal contained a substances called phlogiston. When a substance burned it released all or some of its phlogiston into the air.

14 Problems with Phlogiston Theory When pure metals burn they should weigh less (turns into calx)…however, metals always weigh more when burned, that is the clax always weighed more than the metal. The reverse experiment: If calx is heated, it should remove phlogiston from the air be converted back to the metal…however the Burning Lens experiment by Lavoisier observed “fixed air” being released back into the air.

Tro's "Introductory Chemistry", Chapter 1 15 The Great Burning Lens: Trying to Find Phlogiston - ultimately it was discredited

Tro's "Introductory Chemistry", Chapter 1 16 A Better Theory of Combustion Lavoisier purchased the most accurate scales; scales that would cost over million of dollars today Lavoisier carefully preformed his experiments weighing them before and after each combustion experiment.

17 A Better Theory of Combustion Lavoisier proposed an alternative theory of combustion based on his experiments: 1. When something burns, it can either remove or combine with “fixed-air.” 2. He discovers Oxygen, hydrogen Lavoisier literally, rewrites all chemistry textbooks. Lavoisier’s idea starts modern chemistry based on reproducible experimentation---backed with very accurate measurements. He is executed by a phlogiston believer-political

Lord Kelvin, 1850’s "To measure is to know." "If you can not measure it, you can not improve it." Tro's "Introductory Chemistry", Chapter 1 18

Tro's "Introductory Chemistry", Chapter 1 19 How to Succeed in Chemistry Curiosity and your imagination are your allies Explore and investigate. Quantify and calculate Even small differences can be important! Commitment Work regularly and carefully.

Tro's "Introductory Chemistry", Chapter 1 20 The Best Approach to Learning Chemistry Learn the vocabulary of chemistry. Definitions and terms. How common vocabulary is applied to chemistry. Memorize important information. Names, formulas, and charges of polyatomic ions. Solubility rules. Learn and practice processes. Systematic names and formulas. Dimensional analysis. Do the questions and exercises in the chapter to test your understanding and help you learn the patterns?