BASIC CHEMISTRY REVIEW: 2-1 & 2-2
1.Why were atoms given the name of “atom” which means “unable to be cut?”
they are the smallest unit that is still considered an element
2.What are the 3 basic parts of an atom, what are their charges, and where (in the atom) are they found?
protons: + charge: nucleus
neutrons: no charge: nucleus
electrons: - charge: orbit the nucleus
3.Which 2 parts of an atom are responsible for almost all of the mass of the atom?
1.protons2.neutrons
4.What is the overall charge of an atom?neutral/ no charge
5.What is the overall charge of the nucleus?positive (+)
6a.How do you determine which number on the periodic chart is the Atomic Mass Number?
It is the bigger of the 2 numbers for a chemical symbol
6b.What does the Atomic Number tell you?the number of protons
7a.What is an element?
pure substance that is composed of only 1 kind of atom
7b.How are elements represented or symbolized? 1 or 2 letter symbol; 1st letter capitalized & 2nd letter lower case
8.What is the smallest part of an element that is still that element?atom
9a.What is an isotope?atoms of the same element that have a different # of neutrons
9b.Draw the 3 isotopes of Carbon.How are they similar? How are they different?
SIMILAR: same # of protons & electrons; same chemical properties
DIFFERENT: different # of neutrons so they have a different mass
10.What makes an isotope radioactive?
the nucleus is unstable and breaks down over time
11.List 4 uses for radioactive isotopes.
1.ages of rocks can be determined
2.treat cancer
3.kill bacteria in food
4.used as a "tracer" in human body or as a way to label something in the body
12a.What is a compound?
substance formed by a chemical reaction of 2 or more elements in a specific proportion
Give 2 examples.1.water (H2O)
2.table salt; sodium chloride (NaCl)
13Explain how you know that a compound is not just a mixture of the compound-elements.
because the chemical properties of the compound are not the same as the properties of the individual elements (ex: NaCl; Na is an explosive metal & Cl is a greenish poisonous gas)
14.What information is contained in a chemical formula?
the elements in that compound and the # of atoms of a specific element required to make up that compound
15.In a simplified 2-D model of an atom, what is the maximum number of electrons that fit on the first energy level? 2
On the second energy level?8
On the third energy level?8
16.How many valence electrons does Calcium have?2
17a.What is an ionic bond?a bond between elements where 1 or more electrons are transferred to make that element stable (ion); the attraction between the ions is the bond
17b.Give an example of a compound formed by an ionic bond.
Sodium Chloride; NaCl
18a.What is a covalent bond?
a bond that is formed when electrons are shared to make each element stable
18b.Give an example of a compound formed by an covalent bond.Water; H2O
19.What is a molecule?smallest unit of most compounds
20.Explain how a gecko can climb a wall and not fall off.
the gecko foot has 100's of thousands of small flat-surfaced fibers; this allows the gecko's foot to be in contact witha lot of wall-surface area; the combined Van der Waals forces keeps the gecko on the wall
21.List 3 reasons why water is unique.
1.covers 3/4 of the Earth's surface
2.single most abundant compound in living things
3.unlike most substances, water expands when it freezes
22.Why is a water molecule considered polar?
the water molecule has an uneven distribution of charges so it is called "polar"
23.Describe Oxygen’s charge and why it has that charge.
because oxygen is a bigger atom than hydrogen, it has a stronger attraction for electrons; because the electrons spend more time orbiting oxygen, oxygen takes on a small negative charge; this leaves hydrogen with a small positive charge
24.What is the result of the polarity of water molecules?hydrogen bonds
25.List and give an example of 2 special properties of water.
1.cohesion
ex:drops of water can form on a smooth surface; insects can walk across pond water
2.adhesion
ex:water is drawn from plant roots up through the stem to the leaves; graduated cylinder meniscus
26.How is a mixture different than a compound?
a mixture can be separated by physical means- filtering, scooping, evaporating; a compound is chemically combined
Example of a mixture: NaCl and water (evaporate off water)
peanuts & M&M's (separate by hand)
27a.What are the 2 types of mixtures that can be made with water?
1.solution
2.suspension
27b.How are they different?
if a liquid is a solution, the substance dissolved; in a suspension a substance is evenly distributed and floating in the water while remaining undissolved
28.Define solute.the substance that is dissolved
Example of a solute:NaCl; table salt
29.Define solvent.the substance in which the solute dissolves
Example of a solvent:water
30.Water can react to form which 2 ions?
1.H+
2.OH-
31a.Which pH has the same number of H+ ions as OH- ions?7
31b.A pH of 13 will have more ______ions than a pH of 7. OH-
31c.A pH of 4 will have more ______ions than a pH of 7. H+
32.Circle the pH that is the most acidic.259