Ch. 2 CHEMISTRY

Matter: has mass and takes up space Mass: quantity of matter an object has.

Elements: pure substances that can not be broken down. Each has its own chemical symbol. We find elements arranged on the periodic table of elements. *90% of all living things contain the elements O, C, H, and N. Atoms: Simplest particle of an element.

Molecules: simplest part of a substance Atoms: –Nucleus: core of atom Proton: positive electrical charge Neutron: no charge *Atomic Number: number of protons

Electrons: negative charge particles that orbit in shells around nucleus. –Electrons are the same number as protons.

Compound: 2 or more elements combined together. Ex: Water = H 2 O –The subscript shows the number of atoms of each element. (2= 2 hydrogens) Chemical Reaction: atoms become rearrange, and new bonds form. A new substance is made.

Bonds: energy that holds compounds together Covalent bonds are: 2 atoms that share 1 or more pairs of electrons. Usually between non metals –Ex: water Ionic: formed by electrical attraction between. No actual sharing takes place. Usually between metals. –Ex: Salt = NaCl

Energy Energy is the ability to do work or cause change. State of matter: are solid, liquid and gas. –Reactant: is involved in the chemical reaction. –Product: is the product that is formed by the reaction.

Energy for our bodies are provided mainly by sugars from the foods we eat. These sugars are broken down by chemical reactions that produce the energy.

Exergonic energy: is the release of energy. Endergonic energy: absorption of the energy. Catalysts: reduce the energy needed for the reaction to occur. –Enzymes: catalysts that are used in living things

There is a constant flow of energy in all living things. Most reactions deal with movement of electrons.

Many reactions involve a transfer of electrons called Oxidation-Reduction, or Redox reactions. –Oxidation is the loss of electrons –Reduction is the gain of electrons

Most systems in anything living involve water, or some combination of substances dissolved in water.

Solutions: 1 or more substances dissolved in another substance. –Solute: dissolved in solution. In smaller amount –Solvent: substance in which solute is dissolved –Concentrated: amount of solute in the solution –Saturated: no more solute can be dissolved. * Aqueous solutions: water is the solvent

Mixture: 2 or more substances that have variable composition. –Homogeneous: the same through out. ex: milk –Heterogeneous: different through out. »Ex: rocky road ice cream

Dissociation is the breaking apart of the water molecule into 2 ions of opposite charge. –Acids= have a greater number of hydronium (H) ions. 0-7 on pH scale –Base (alkali) have a greater number of hydroxide ions (OH) 7-14 on pH scale pH is the way of measuring H or OH ions. It stands for Potential Hydrogen –Buffers are substances use to neutralize

Physical properties and changes describe what is observed by the senses and the changes in appearance only. The substance remains the same. –Ex: color, shape, mass, density Chemical Properties and Changes describe how a substance reacts with other substances and the new substances that are formed. –Ex. Rust, baking