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

electron

neutron

proton

• 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 = H2O

–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