Chapter 1: Matter and Change

1.1 Chemistry Chemistry is the study of the composition of substances and the changes they undergo. Can be as simple as the science behind ice melting, to as complicated as impulses carried by your nerve cells. The “Central Science” Contributes to biology, geology and physics. Chinese/Japanese character for chemistry literally means “change study”

1.2 The Scientific Method You’ve covered this before in other classes. Pg. 4-5 of text. Theory: A well-tested explanation for a natural event. Law: A summary of observations about natural events.

1.3 Properties of Matter What is matter? Substances Matter is anything that takes up space (has volume) and has mass. Mass: The amount of matter than an object contains. Substances Table sugar is 100% sugar (table sugar is sucrose). Table sugar is a substance A substance is a kind of matter that has a uniform and definite composition. Is lemonade a substance? Air? Water?

Physical Properties All samples of a substance have identical physical properties. A physical property is a quality or condition of a substance that can be observed or measured without changing the substances composition. This is really wordy. Give me examples. Color, mass, odor, hardness, density, melting point, and boiling point are all examples. We use physical properties to help identify substances.

Example Pg. 8 of textbook, table 1.2 If I give you a white solid that melts at 800°C, what substance would it probably be? How about a colorless liquid that couldn’t be frozen in your home’s freezer? Hint: Melting point and freezing point are the same thing.

Homework Read pg. 3-8 Do: Pg. 6, #4 Pg. 7, #5 Pg. 8 #6 Pg. 22-25, #29, 30, 54, 59a, 62, 65

1.4 The States of Matter The same substance, like water, can exist in multiple forms. Ice, water, steam Still all water, just different forms of it. These forms are called physical states. Physical states are a physical property of the matter

Solids Three main states of matter Solids Shape does not depend upon the shape of the container Solids are matter that has a definite shape and volume. Particles packed together tightly. Most are incompressible, and expand only slightly when heated.

Liquids Liquids Particles in a liquid are in contact with each other, but packed less tightly than in a solid. Almost incompressible, but expand when heated. Liquid flows Takes the shape of the container in which it is placed However, volume remains the same for a given sample, regardless of the container.

Gases Gasses Flow to take the shape of the container that holds them Particles spaced far apart Expand without limit to fill any space Easily compressible Takes both shape and volume of container

Gas ≠ Vapor Term gas is reserved for a substance that exists in the gaseous state at room temperature The word vapor describes a substance, although in the gaseous state, is generally a solid or liquid at room temperature. Water is a liquid, though it can be a vapor when heated

1.5 Physical Changes Matter can be changed in many ways without altering its composition. Cutting, grinding, bending, melting, freezing, boiling These transformations that do not alter a substance’s composition are called physical changes.

Homework Read Do Pg. 9 – 11 (up until mixtures) Pg. 10, #7 and 8

1.6 Mixtures What is it to create a mixture? A salad is a mixture. Soil is a mixture. Lemonade is a mixture. Air is a mixture. A mixture consists of a physical blend of two or more substances. NOT substances.

Granite, salad, air, kool-aid are all mixtures. Is there a difference in how they look though? In general? There are different types of mixtures. Heterogeneous Mixtures Not uniform in composition. If you sample one portion of the mixture, will be different from any other portion. Which of the above would be a heterogeneous mixture?

Homogeneous Mixture Completely uniform composition Any given sample should be the same Composition can still vary

Phase Any part of a system with uniform composition and properties Homogeneous mixtures have one phase Heterogeneous mixtures have two or more phases Vinegar and oil dressing has 2 phases, an oil phase and a water phase

1.7 Elements and Compounds By physically separating mixtures, you can obtain pure substances Remember, substances have uniform and definite compositions Two groups of pure substances Elements Compounds

Elements Simplest form of matter that can exist under normal laboratory conditions Cannot be separated into simpler forms by chemical reactions Examples Iron, sulfur, carbon, hydrogen, oxygen Fe, S, C, H2

Compounds Substances that can be separated into simpler substances only by chemical reactions Made when two or more elements combine chemically Examples: Water (H2O), octane (C8H18) Page 15 summarizes with flow-chart

Homework 12-14, 36, 38, 40, 56

1.8 Chemical Symbols All matter in the universe is made of elements. Each element is represented by a chemical symbol. Generally, chemical symbol consists of the first one or two letters of the name of the element. Carbon  C Lithium  Li Neon  Ne

First letter of symbol ALWAYS capitalized. Not always the case though. Some elements are derived from older Latin names. (pg. 17) Sodium  Na (Natrium) Copper  Cu (Cuprum) Gold  Au (Aurum) Lead  Pb (Plumbum) First letter of symbol ALWAYS capitalized. Second letter (if applicable) always lowercase.

1.9 Chemical Reactions In a chemical reaction, one or more of the substances change into a new substance. The substance(s) you start with, called the reactant(s). The substance(s) you end with, called the product(s)  represents “are changed into” Example, iron and sulfur chemical react to form iron sulfide.

Iron + Sulfur  Iron sulfide Can be viewed as: Iron + Sulfur  Iron sulfide reactants product Indications of a chemical reaction Energy given off or taken in (becomes warmer or colder) Color change Production of a gas or solid Note: Some of these can occur during a physical change as well.

Chemical Properties Just like every substance has physical properties, all have chemical properties. The ability to undergo chemical reactions and to form new substances. Only observed when a substance undergoes a change in composition (and therefore a chemical change) Words like rot, rust, decompose, ferment, corrode, grow, decay, sprout, react usually signify a chemical change.

1.10 Conservation of Mass Law of Conservation of Mass In any physical or chemical reaction, mass is neither created nor destroyed; it is conserved In other words, the mass of the products equals the mass of the reactants

Questions Classify the following changes as physical or chemical Bread is baked Salt dissolved in water Milk spoils A snowflake melts Why is the conservation of mass a law and not a theory? When powered iron is left exposed to the air it rusts. Explain why the rust weighs more than the original powered iron. Hydrogen and oxygen react chemically to form water. How much water would be formed if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?