Bio Chapter 2

Matter- anything that occupies space and has mass. \n Mass- a measure of the amount of material in an \n object \n Element- a substance that cannot be broken \n down into other substances by chemical reactions

Trace elements- required in only very small \n amounts and are essential for life

Compounds- substances that contain two or more elements in a \n fixed ratio

Atom- is the smallest unit of matter

Proton- is positively charged \n Electron- is negatively charged \n Neutron- is electrically neutral

Atomic number- All atoms of a particular element have the same unique \n number of protons

Mass number- the sum of the number of protons and neutrons in its nucleus

Isotopes- have the same number of protons and \n behave identically in chemical reactions, but they \n have different numbers of neutrons \n Radioactive isotope- one in which the nucleus \n decays spontaneously

Chemical bonds- atoms staying close together, held by attractions

Ions- atoms or molecules that are electrically \n charged as a result of gaining or losing electrons \n Ionic bonds- formed between oppositely charged \n ions \n Ionic compounds- held together by ionic bonds

Covalent bond- forms when two atoms share one or \n more pairs of electrons

• are the strongest bond
• holds atoms together in a molecule

Molecule- group of atoms

polar molecule- one with an uneven distribution of charge \n hydrogen bonds- weak electrical attractions due to the polarity of water

chemical reactions- changes in the chemical composition of matter \n reactants- the starting materials \n products- the end materials

water content in cells- 70-95%

cohesion- tendency of molecules of the same kind to stick \n together

Evaporative cooling- when a substance \n evaporates and the surface of the liquid remaining \n behind cools down

solution- a liquid consisting of a homogeneous \n mixture of two or more substances

solvent- dissolving agent

solute- what’s being dissolved

solution- resulting mixture

aqueous solution- when water is the solvent

acid- releases H

base- accepts H and removes it from a solution

pH scale- measurement of the hydrogen ion H concentration in a solution

buffer- minimizes changes in pH \n