An Introduction to Chemistry Chapter 1 Hein and Arena Eugene Passer Chemistry Department Bronx Community College © John Wiley and Sons, Inc Version th Edition

What is a Science? The observation, identification, description, experimental investigation, and theoretical explanation of natural phenomena.

Natural Phenomena experimentally investigate theoretically explain observe describeidentify

Chemistry The science of the composition, structure, properties and reactions of matter, especially of atomic and molecular systems.

Matter compositionstructure propertiesreactions

1.4 A Scientific Approach to Problem Solving

Problem Solving 1.Define the problem by recognizing it and stating it clearly. In science this is called an observation. 2. Propose solutions to the problem. In science this is called a hypothesis. 3. Decide the best way to solve the problem. In science we perform an experiment.

1.5 The Scientific Method

1. Observation Phenomenon Hypothsis Expriment Collect data/Analysis Interpretation/Conclusion Scientific theory Scientific law

Law: Statement of natural phenomena to which no exceptions are known under the given conditions. A law is not an explanation. Hypothesis: A tentative explanation of certain facts that provide a basis for further experimentation. Theory: Well- established hypothesis. An explanation of the general principles of certain phenomena with considerable evidence or facts to support it.

2. Analyze the data to find trends (regularities). 3. Formulate a hypothesis that will account for the data and that can be tested by further experimentation. 1. Collect facts or data that are relevant to the problem or question at hand. This is usually done by experimentation.

5. Modify the hypothesis to ensure compatibility with the experimental data. 4. Plan and do additional experiments to test the hypothesis.

EXPLANATIONS

1.6 The Particulate Nature of Matter

Matter can be invisible. Air is matter, but it cannot be seen. Matter appears to be continuous and unbroken. ─Matter is actually discontinuous. It is made up of tiny particles call atoms. Matter is anything that has mass and occupies space.

1.3 An apparently empty test tube is submerged, mouth downward in water. Only a small volume of water rises into the tube, which is actually filled with invisible matter–air.

1.7 Physical States of Matter

Shape Definite - does not change. It is independent of its container. Volume Definite ParticlesParticles are close together. They cling rigidly to each other. SOLIDS CompressibilityVery slight–less than liquids and gases.

Solid Amorphous Solid Particles lack a regular internal arrangement Glass, plastics, gels Crystalline Solid Particles exist in regular, repeating three-dimensional geometric patterns. Diamond, metals, salts A solid can be either crystalline or amorphous. Which one it is depends on the internal arrangement of the particles that constitute the solid.amorphous

Amorphous: without shape or form.

Shape Not definite - assumes the shape of its container. Volume Definite Particles Particles are close together. Particles are held together by strong attractive forces. They stick firmly but not rigidly to each other. They can move freely throughout the volume of the liquid. LIQUIDS CompressibilityVery slight–greater than solids, less than gases.

GASES Shape No fixed shape. Volume Indefinite. ParticlesParticles are far apart compared to liquids and solids. Particles move independently of each other.

GASES Compressibility The actual volume of the gas particles is small compared to the volume of space occupied by the gas. –Because of this a gas can be compressed into a very small volume or expanded almost indefinitely.

1.8 Classifying Matter

Matter refers to all of the materials that make up the universe.

Substance A particular kind of matter that has a fixed composition and distinct properties. Examples ammonia, water, and oxygen.

Homogeneous Matter Matter that is uniform in appearance and with uniform properties throughout. Examples

Heterogeneous Matter Matter with two or more physically distinct phases present. Examples

Homogeneous Heterogeneous

Phase A homogenous part of a system separated from other parts by physical boundaries. Examples In an ice water mixture, ice is the solid phase and water is the liquid phase.

Mixture Matter containing 2 or more substances that are present in variable amounts. Mixtures are variable in composition. They can be homogeneous or heterogeneous.

Homogeneous Mixture (Solution) A homogeneous mixture of 2 or more substances. It has one phase. Example Sugar and water. Before the sugar and water are mixed, each is a separate phase. After mixing the sugar is evenly dispersed throughout the volume of the water.

Example Heterogeneous Mixture A heterogeneous mixture consists of 2 or more phases.

Example Heterogeneous Mixture A heterogeneous mixture consists of 2 or more phases.

1.6 Classification of matter: A pure substance is always homogeneous in composition, whereas a mixture always contains two or more substances and may be either homogeneous or heterogeneous.