Section 2 • Matter is anything that occupies space and has mass. • There are three states of matter: gas, liquid, and solids Same # of protons as electrons • Atoms are composed of subatomic particles • A proton is positively charged • Electron is negatively charged • Neutron is electrically neutral • Electrons rotate and orbit the nucleus
Elements
• atoms differ in numbers of subatomic particles
Neutrons:
• no charge
Isotopes
• Forms of an element that differ in the number of neutrons their atoms carry • Changes the mass number
Mass number • total number of protons and neutrons in the nucleus
Radioisotope
• isotope with an unstable nucleus, such as carbon
Radioactive decay • process by which atoms oaf a radioisotope spontaneously break down and decay over time
Electrons
• electrons travel around the nucleus in different orbitals (shells) • 1st shell can hold 2 • 2nd shell can hold 8 • 3rd shell can hold 8
Vacancies
• Atoms are the "happiest" when they haven vacancies in their outer shell • Atoms with vacancies in their outer shells tend to interact with other atoms
Ions
• when you lose or gain electrons • negative charge of an electron balances the positive charge of a proton in the nucleus
Chemical bonds and molecules • molecule- 2 or more atoms • compound- 2 or more atoms and atoms are more than 1 element • EX: H20 CH4; H2 and O2 are molecules but not compounds
Chemical bonds • Ionic bond- strong attraction formed between ions of opposite charge • covalent bond- two atoms sharing a pair of electrons • Hydrogen bonds- opposites attract form and break more easily than covalent or ionic bonds; not chemical bonds; do not form molecules
Section 3 • water- all living organisms are mostly water, all chemical reactions happen in water • 1. Cohesion (surface tension)- water molecules stick together as a result of hydrogen bonding • surface tension- the difficulty it takes to break the water • 2. Water dissolves substances- hydrophilic(water loving) - substance that dissolves easily in water • Hydrophobic (water fearing)- substance resists dissolving in water • water is an excellent solvent • 3. Temperature stability- important part of homeostasis- water absorbed heat (energy) than other liquids before the temp rises • Temperature- measure of molecular movement • Evaporative cooling removes heat from the earth and other organisms • heat is sued to break hydrogen bonds instead of raise the temperature • 4. Ice is lighter than water - density of ice is lower than liquid water EX: why ice floats • since ice floats, ponds, lakes, and even the oceans do not freeze solid. If so it couldn't support life. • Lattice- forms air pockets in ice • pH- water molecules separate into hydrogen ions and hydroxide ions • pH= measure of the number of hydrogen ions in a solution *more hydrogen less pH • pure water has a neutral pH of 7
Acids and Bases • Acid- substance that releases hydrogen ions in water; pH less than 7 • Base- substance that accepts hydrogen ions in water; pH greater than 7
Buffersß
• buffers resist change in pH (keep in specific range) • most molecules of life work within a narrow range of pH • they accept H+ ions when in excess • they donate H+ ions when depleted
Organic molecules • molecules of life- carbs, proteins, etc. • Why is carbon so important to life? • Carbon is a versatile atom • 4 electrons in an outer shell that holds 8 • Carbon can share its electrons to create 4 covalent bonds
-----------------------------------------------------------------------------------------------------------------------------------------
9/10
The nucleotide monomoer, DNA • A nucleotide consists of three components- 1. sugar, 2. phosphates, 3. base • each DNA has one of the following bases, Adenine, Guanine, Thymine, and Cytosine • hook whatever nucleotide you want together • order of the bases holds the