Chapter 2: Introduction to Chemistry

Nature of Matter Matter - Is anything that has mass and volume. –Physical properties of matter: Color, texture, taste, hardness. Melting Point -The point at which a solid becomes liquid. Boiling Point -Temperature at which liquid comes to a boil. Phases - The stages resulting from chemical change (liquid, gas, solid). Example ice, water, water vapor. –Chemical properties of matter: A substances ability to change into a new substance as a result of chemical change.

The Atom Atom - The basic unit of matter. –Nucleus: Center of an atom, it is made up of protons (+ charged particle) and neutrons (neutral), the two have an equal mass. –Electrons: Are (- charged) particles and are equal to the number of protons in an atom. They aren’t found in the nucleus They orbit the nucleus at high speeds because of their energy level.

More on the Atom The number of protons is = to the number of electrons, so the whole atom is neutral. The Atomic # is the number of protons in the atom, this number can’t change it makes the atom what it is. (Always found in the upper left corner of the box on the periodic table). The Mass # is the number of protons + neutrons in the atom. (Usually found on the bottom or upper right corner of the box on the periodic table)

Elements Elements are pure substances made entirely of one type of atom. There are 100+ different types of elements, but only about 24 are commonly found in organisms. Each elements is represented by a chemical symbol (examples; H, Na, etc.) All of the elements are organized in the periodic table.

Isotopes Isotopes are atoms of the same element with different numbers of neutrons, they are identified by the mass #. Some isotopes are radioactive. Radioactive isotopes have unstable nuclei and breakdown over time, because of this they can be dangerous but also have many uses; cancer treatment, tracers in medicine, kill bacteria.

Chemical Compounds Compound - Two or more elements in definite proportions –In nature most elements are found combined with others. (Example: H 2 O, 2 H atoms for every 1 O atom). –A compound is a new substance with different properties than the elements in it.

Chemical Bonds Chemical Bonds- Chemical compounds are held together by bonds. The electrons of atoms are involved in forming the bond. –Bonds form because every atom wants to be stable. In order for the atom to be stable it must fill its outer energy level.

Types of Bonds 2 Types of Bonds –1.) Ionic Bond: Electrons are transferred. An ion (atom with a charge) forms because of an unequal # of protons + electrons. The opposite charges of the ions holds them together.

Types of Bonds 2 Types of Bonds –2.) Covalent Bond: Electrons are shared between two atoms making them stable and forms a molecule.

Chemical Reactions & Enzymes Chemical Reaction -Process that changes one set of chemicals into another. – Reactant(enters reaction)  Product (produced) –Some reactions are fast ex. Burning –Some reactions are slow ex.iron rust –A reaction always involves breaking bonds and forming new bonds – Energy is either released or absorbed.

Chemical Reactions & Enzymes Exergonic Reaction - An energy releasing reaction, may occur spontaneously. –Example: 2H 2 + O 2  2H 2 O Endergonic Reaction - An energy absorbing reaction, does not occur without a source of energy. –Example: 2H 2 + O 2  2H 2 O Living things need a source of energy for their endergonic reactions to take place. Activation Energy: Energy required to start a reaction. Enzymes: are catalysts that lower activation energy and make reactions happen faster.