Notes, summaries, assignments, exams, and problems for Chemistry

Physical and Chemical Changes

Physical changes do not cause new substances to appear. However, chemical changes produce substances that were not present before the transformation, as a result of a chemical change.

Reagents and Products in a Chemical Reaction

Reagents are the pure substances that are combined together in order to produce a chemical reaction. Products are the substances produced as a result of combining reagents in order to produce a chemical reaction.

Characteristics of Chemical Changes

• Energy is exchanged throughout the course of a chemical reaction.
• Reversible and irreversible reactions.
• The states of aggregation.

Collision Theory in Chemical Reactions

According to collision theory, chemical reactions take place because the molecules... Continue reading "Understanding Chemical Reactions and Matter Transformation" »

Galvanic Reaction in the Mouth

Biting on aluminum foil can be painful and is usually noticed if you have metal in your mouth from dental work (e.g., fillings, crowns). Basically, when you bite on foil, you set up a battery in your mouth, and the electrical current stimulates nerve endings in your tooth. Here is what happens:

• Pressure from biting brings two dissimilar metals (aluminum foil, mercury in fillings, or gold in crowns) in contact in a moist, salty environment (saliva).
• The two metals have an **electrochemical potential difference** or voltage across them.
• Electrons flow from the foil into the tooth (i.e., **electrical current**).
• The current gets conducted into the tooth's root, usually by the filling or crown.
• The current sets off a nerve

The pH Scale and Acidity Measurement

The pH scale is a system that measures the acidity of a substance. It is ranked from 1 to 14, with 1 being the most acidic and 14 being the most alkaline; 7 is neutral. The pH represents the concentration of hydrogen ions (H+) in a substance and is measured using the pH scale.

Buffers: Maintaining pH Balance

Buffers are substances that tend to maintain a constant pH by liberating or capturing H+ ions. If blood becomes too acidic, bicarbonate accepts H+ ions, and carbonic acid is formed. If it becomes too basic, carbonic acid liberates H+ ions to interact with OH- ions to form water.

Major Classes of Biomolecules

Biomolecules are any molecules produced by a living organism. The four main groups are:

• Nucleic Acids
• Proteins
• Carbohydrates
• Lipids

Examples

Understanding States of Matter

Properties of Solids, Liquids, and Gases

• All are states of matter and are composed of particles.

Solids vs. Liquids

• In solids, particles are very close together and vibrate in fixed positions. Solids have a definite shape and definite volume.
• In liquids, particles are close together but can move past each other. Liquids do not have a definite shape but have a definite volume, taking the shape of their container.

Liquids and Gases

• Both liquids and gases do not have a definite shape; they take the shape of their container.
• Liquids and gases can flow because their molecules are moving and can slide over each other.

Gases

• In gases, particles are far apart and move randomly and rapidly.
• Common examples of gases include oxygen,

Production

Vocabulary: Dimensions

• Dimension: Big/Small
• Height: High/Low
• Depth: Deep/Shallow
• Width: Wide/Narrow
• Length: Long/Short
• Strength: Strong/Weak
• Thickness: Thick/Thin

Production 1

Improved quality control. Paper is an industrial process. It is the basic raw material. Increased productivity levels. The large store (for) finished product. Large factories use assembly lines. The company moved into large-scale manufacturing. The manufacturing (is the responsibility) of the production manager.

Complete the Sentences:

• Known as a batch.
• Is to assemble.
• Inputs to outputs.
• Is known as purchasing.
• Is called a component.
• Is to optimize.

Text:

We are making good progress with the new factory site layout: fixtures, equipment, machinery, workshops, etc. The present... Continue reading "Vocabulary for Manufacturing, Materials, and Energy" »

Fundamental Concepts in the Origins of Life

• Biogenesis: The principle that states all living things come from other living things.
• Spontaneous Generation: The theory that living things could arise from non-living matter.
• Radiometric Dating: A technique used to establish the age of materials.
• Isotope: Atoms of the same element with different mass numbers.
• Mass Number: The total number of protons and neutrons in the nucleus.
• Radioactive Decay: The process where a nucleus releases particles, radiant energy, or both.
• Radioactive Isotope: An isotope that undergoes radioactive decay.
• Half-life: The length of time an assembly of an isotope takes to decay by one-half.
• Microsphere: A spherical structure composed of protein molecules.
• Coacervate: A collection

Chapter 1 : Matter and change

Branches of chemistry

Organic Chemistry – the study of most carbon-containing compounds.

Inorganic Chemistry – the study of most non-carbon-containing compounds.

Physical Chemistry – the study of the properties and changes of matter and their relation to energy.

Biochemistry – the study of substances and processes occurring in living things.

Analytical Chemistry – the identification of the components and composition of materials.

Theoretical chemistry – the use of mathematics and computers to understand the principles behind observed chemical behaviour and to design and predict the properties of new compounds.

Matter

Atom – the smallest unit of an element that maintains the chemical identity of that element.

Mixture

A mixture is a physical blend of two or more components.

Heterogeneous mixture

A mixture in which the composition is not uniform throughout is a heterogeneous mixture.

Homogeneous mixture

A homogeneous mixture is a mixture in which the composition is uniform throughout. Another name of homogeneous mixture is a solution.

Phase

The term phase is used to describe any part of a sample with a uniform composition and properties.

Filtration

The process that separates a solid from the liquid in a heterogeneous mixture is called filtration.

Distillation

One way to separate water from the other components in tap water is through a process called distillation.

Properties of Matter

Mass

The matter of an object is a measure of the amount of matter the object... Continue reading "Understanding Mixtures, Phases, and Chemical Reactions" »

Fundamental Concepts in Physical Science

I. Atomic and Chemical Structure

Basic Constituents of Matter

Atom

The basic or fundamental constituent of matter.

Element

A species of atoms having the same number of protons in their atomic nuclei.

Molecule

An electrically neutral group of two or more atoms of the same element held together by chemical bonds.

Compound

An electrically neutral group of two or more atoms of different elements held together by chemical bonds.

Ion

An atom or molecule in which the number of electrons is not equal to the number of protons. (Note: Extracting electrons can lead to plasma.)

Isotope

An element made up of atoms that have the same number of protons (atomic number) but a different number of neutrons (mass number).

Periodic Table