Chem 1123 Unit 1: Introduction to Chemistry, Matter, and Chemical Calculations

Introduction to Chemistry and Chemical Calculations

Definition of Chemistry

Chemistry is the study of the composition, structure, properties, and reactions of substances. It explores how substances interact, combine, and change to form new substances.

• Composition: What substances are made of.

• Structure: How the components of a substance are arranged.

• Properties: Characteristics that define a substance.

• Reactions: How substances transform into others.

Chemicals in Daily Life

Chemicals are present in many everyday items and processes.

• Clean drinking water

• Plastics

• Baking soda

• Detergents

• Gasoline

• Processed foods

• Medicines

What is a Chemical?

A chemical is any substance used in or produced by a chemical process. All matter is made up of chemicals.

• Examples: Water (H2O), table salt (NaCl), sugar (C12H22O11).

Chemical Reactions

Chemical reactions involve the transformation of substances into new substances. They can occur in various contexts:

• Using a battery

• Digesting food

• Burning a candle

During a chemical reaction, reactants are converted into products, often with the release or absorption of energy.

Classification of Matter

Definition of Matter

Matter is anything that has mass and takes up space (has volume). All substances (chemicals) are forms of matter.

Pure Substances

A pure substance contains only one kind of matter and has a specific composition. There are two types:

• Elements: Substances that cannot be broken down into simpler substances by chemical means. Each element is listed on the periodic table and is made up of one type of atom.

• Compounds: Substances composed of two or more elements chemically combined in fixed proportions. Compounds can be broken down into elements by chemical means.

Example: Water (H2O) is a compound; gold (Au) is an element.

Mixtures

A mixture consists of two or more substances that are physically mixed, not chemically combined. Mixtures can be separated by physical methods.

• Homogeneous mixtures (solutions): The composition is uniform throughout; the different parts are not visible.

• Heterogeneous mixtures: The composition varies from one part to another; the different parts are visible.

Examples: Salt water (homogeneous), salad (heterogeneous).

Examples of Physical Methods of Separation

• Filtration

• Evaporation

• Distillation

• Chromatography

Classification of Matter Table

Type	Description	Examples
Element	Pure substance, cannot be broken down	Oxygen (O2), Gold (Au)
Compound	Pure substance, two or more elements chemically combined	Water (H2O), Sodium chloride (NaCl)
Homogeneous Mixture	Uniform composition throughout	Salt water, air
Heterogeneous Mixture	Non-uniform composition, visible parts	Salad, sand in water

Elements and Symbols

Element Symbols

An element symbol represents the name of an element. Symbols use one or two letters:

• First letter is always capitalized; second letter (if present) is lowercase.

• Examples: C = carbon, N = nitrogen, F = fluorine, Co = cobalt, Ca = calcium, Mg = magnesium.

Origin of Element Names

• Carbon: From Latin carbo (coal).

• Iodine: From Greek for violet.

• Curium: Named in honor of Marie Curie.

Common Element Symbols and Names

Symbol	Name	Origin
Cu	Copper	Cuprum (Latin)
Fe	Iron	Ferrum (Latin)
Au	Gold	Aurum (Latin)

Writing Element Symbols

• Do not use capital letters for both letters.

• Write the first letter in uppercase, the second (if present) in lowercase.

• Example: Co (cobalt), not CO.

Memory Work: Element Names and Symbols

• Be familiar with the correct spelling and symbols for the first 21 elements and other common elements.

• Spelling and capitalization are important for clarity and accuracy.

Compounds and Formulas

Compound Formulas

Compound formulas show the elements that make up the compound. Subscripts indicate the proportions of the elements.

• Table salt: NaCl

• Water: H2O

• Table sugar: C12H22O11

The Scientific Method

Definition and Steps

The scientific method is a general approach to problem-solving and understanding natural phenomena. It involves:

1. Observation: Gathering information about a phenomenon.

2. Hypothesis: Proposing a tentative explanation or prediction.

3. Experimentation: Testing the hypothesis with controlled experiments.

4. Analysis: Interpreting the data and drawing conclusions.

5. Theory: If supported by repeated experiments, the hypothesis may become a theory.

Identifying Steps in the Scientific Method

• Distinguish between observation, hypothesis, experiment, and conclusion in scientific reasoning.

Practice and Application

Learning Checks

• Identify whether a sample is a pure substance or a mixture.

• Classify mixtures as homogeneous or heterogeneous.

• Recognize correct element symbols and names.

Key Terms and Definitions

• Element: A substance that cannot be broken down into simpler substances by chemical means.

• Compound: A substance composed of two or more elements chemically combined in fixed proportions.

• Mixture: A physical combination of two or more substances.

• Homogeneous mixture: Uniform composition throughout.

• Heterogeneous mixture: Non-uniform composition; different parts are visible.

• Chemical reaction: A process in which substances are transformed into new substances.

• Scientific method: A systematic approach to investigation and problem-solving in science.

Formulas and Equations

• General chemical reaction:

$\text{Reactants} \rightarrow \text{Products}$

• Water formula:

$\text{H}_2\text{O}$

• Table salt formula:

$\text{NaCl}$

• Table sugar formula:

$\text{C}_{12}\text{H}_{22}\text{O}_{11}$