Chemistry: Matter, Properties, and Chemical Changes

Posted on Dec 18, 2024 in Chemistry

Chemistry: A Physical Science

Science is the knowledge obtained by observing natural events and conditions to discover facts and formulate laws or principles. Chemistry is the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes. A chemical is any substance with a definite composition.

Branches of Chemistry

  • Organic Chemistry: The study of materials with carbon.
  • Inorganic Chemistry: The study of non-organic materials.
  • Physical Chemistry: The study of the properties of matter.
  • Analytical Chemistry: The identification of materials.
  • Biochemistry: The study of the chemistry of living things.
  • Theoretical Chemistry: Predicting the properties of new materials.

Types of Chemical Research

  • Basic Research: Basic research includes the study of the properties of a chemical. It also includes the study of what happens when two chemicals are mixed. It sometimes results in a new product or technology.
  • Applied Research: The goal of applied research is to solve problems in chemistry. Applied research includes finding materials with certain properties.
  • Technological Development: The goal of technological development is to come up with new products and processes that improve the quality of life. They can result from knowledge gained in basic and applied research.

Chemistry and Our World

Chemistry helps us understand our world. Chemistry can help us better understand the world around us. We can find sources of information containing scientific claims, and if it’s not valid, knowing some chemistry can help us assess the validity of the claims.

Current Events: Radon Gas: A substance is radioactive if its atoms break apart, or decay. When atoms decay, they emit radiation in the form of subatomic particles and energy. The Environmental Protection Agency has stated that the amount of radioactive material in most granite is not enough to be dangerous.

Chemistry helps us change and improve our world. Chemists are concerned with the study of the substances around them and the changes those substances undergo. The knowledge they’ve gained has helped them change and improve our world.

Chemists: Past and Present

Chemists of the Past: Alchemy is an ancient field of study from which the field of chemistry eventually developed. The word “chemistry” comes from the word “alchemy.” The study of alchemy was more a philosophical tradition than a science. One goal of alchemists was to discover a way to turn base metals into precious metals, such as gold and silver. Like scientists, alchemists tested, heated, mixed, crushed, and burned all kinds of substances to unravel the mysteries of those substances.

Chemical innovations that improve our lives include:

  • Medications for healing illnesses
  • Purified metals for constructing machines
  • Gunpowder
  • Fertilizers for improving crop quality
  • Cleansers for improving sanitary conditions
  • Inks for writing

Chemists Today: Chemical sciences are making advances in pharmaceuticals, forensics, and green chemistry.

  • Pharmaceutical chemists currently use highly advanced computer modeling techniques to build molecules with desired properties.
  • Forensic chemists analyze evidence such as hair samples, bloodstains, fingerprints, and paint chips from crime scenes.
  • Green chemists develop products and processes that minimize the production of substances harmful to society.

Matter and Its Properties

Matter and Its Properties: Matter has two properties: it takes up space, and it has mass. Atoms are the building blocks of matter. An element is a pure substance that cannot be broken down into simpler, stable substances. Carbon and gold are elements. A compound can be broken down into simpler, stable substances. For example, water is a compound made of two elements. All substances have characteristic properties. Properties can help reveal the identity of an unknown substance.

Extensive and Intensive Properties

  • Extensive properties depend on the amount of matter that is present. Extensive properties include volume, mass, and the amount of energy in an object.
  • In contrast, intensive properties do not depend on the amount of matter present. Such properties include melting point, boiling point, and density.

Physical Properties and Physical Changes

A physical property can be observed or measured without changing the identity of the substance. One physical property of a substance is its boiling point. A change in a substance that does not involve a change in the identity of the substance is called a physical change. Examples of physical changes include grinding, cutting, melting, and boiling.

Changes in State

The three common states of matter are solid, liquid, and gas. The change of matter from one state to another is called a change of state. A fourth state of matter, plasma, is found in fluorescent bulbs and stars. A plasma has a high temperature, and its matter is made up of charged particles. Like a gas, plasma takes the shape of its container. Unlike gas, its particles can be influenced by electrical charges.

Chemical Properties and Chemical Changes

A chemical property relates to the ability of a substance to undergo changes that transform it into different substances. A chemical change is a change in which one or more substances are converted into different substances. The substances that react in a chemical change are called the reactants. The substances formed by the chemical change are called the products. A chemical reaction is usually presented as an equation: Ex/ iron + chloride = iron(III) chloride. Chemical reactions form products whose properties can differ greatly from the properties of the reactants.

Energy and Changes in Matter

Every physical and chemical change requires energy. Energy can be absorbed or released by one of the substances involved in the change. However, even if some of the energy has changed form, the total energy in the system remains the same. This concept is called the law of conservation of energy.

Pure Substances and Mixtures

Matter can be a pure substance or a mixture. A pure substance can be either an element or a compound. Mixtures, in contrast, contain more than one substance. The properties within a mixture can vary from sample to sample.

Mixtures

A mixture is called homogeneous if it is uniform in composition. In other words, a homogeneous mixture looks the same throughout the entire mixture. Homogeneous mixtures are also called solutions. A mixture is called heterogeneous if it’s not uniform throughout.

(CHART)

  1. Matter
  2. Can it be separated?
  3. Yes (Mixtures) (Is the composition uniform?)
    • Yes (Homogeneous mixtures: air, sugar in water, stainless steel)
    • No (Heterogeneous mixtures: granite, wood, blood)
  4. No (Pure substances) (Can it be decomposed by ordinary chemical means?)
    • Yes (Compounds: water, sodium chloride, sucrose)
    • No (Elements: Gold, aluminum, oxygen, chlorine)

Separating Mixtures

Filters separate parts of a mixture using the property of particle size. Other methods of separating mixtures include using centrifuges and chromatography.

Pure Substances

Any sample of a pure substance is homogeneous. A pure substance has a fixed composition and differs from a mixture in the following ways:

  • Every sample of a pure substance has the same physical and chemical properties. These properties are so specific they can be used to identify the substance.
  • Every sample of a pure substance has the same composition as every other sample.

Breaking Down Compounds

Pure substances are either compounds or elements. A compound can only be broken down into two or more simpler compounds or elements by a chemical change. In contrast, a mixture can be separated by the use of its physical properties.

Laboratory Chemicals and Purity

Some Grades of Chemical Purity:

  • Primary standard reagents
  • ACS (American Chemical Society-specified reagents)
  • USP (United States Pharmacopoeia)
  • CP (chemically pure: purer than technical grade)
  • NF (National Formulary specifications)
  • FCC (Food Chemical Code specifications)
  • Technical (industrial chemicals)

Elements

Elements: The periodic table organizes elements by their chemical properties. Some symbols have arisen from the element’s name in other modern languages, or from ancient Latin or German names. For example, the symbol for iron, Fe, comes from the Latin word ferrum. The vertical columns of the periodic table are named groups. The elements in a group are referred to as a family. The horizontal rows of elements in the periodic table are called periods. Physical and chemical properties change in a somewhat regular pattern as you move from left to right across a period. Elements that are close to each other in the same periodic table tend to be more similar than elements that are farther apart.

Metals

Some elements are metals. The periodic table is divided into two main sections: metals and nonmetals. A metal is an element that is a good electrical conductor and a good heat conductor. At room temperature, most metals are solids. Most metals are also malleable. Metals also tend to be ductile (COPPER).

Nonmetals and Metalloids

Some elements are nonmetals or metalloids. A nonmetal is an element that is a poor conductor of heat and electricity. Many nonmetals are gases at room temperature. These include nitrogen, oxygen, fluorine, and chlorine. The solid nonmetals include carbon, sulfur, and iodine.

Noble Gases

Noble Gases: Noble gases are generally unreactive. Low reactivity makes the noble gases very different from the other families of elements.

Metalloids

Metalloids: A metalloid is an element that has some characteristics of metals and some characteristics of nonmetals. All metalloids are solids at room temperature. They tend to be less malleable than metals but not as brittle as nonmetals.

Elements Review

  • List 4 nonmetal elements: Hydrogen, carbon, neon, and chlorine.
  • List 4 metal elements: Iron, calcium, aluminum, sodium.
  • List 4 metalloids: Silicon, carbon, sulfur, arsenic.
  • Write the name of the following elements:
    • O: Oxygen
    • S: Sulfur
    • Cu: Copper
    • Ag: Silver
    • Fe: Iron
    • N: Nitrogen
    • Ca: Calcium
    • Hg: Mercury