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Chemistry Unit 2 – Text
Assignments
Assigned Reading and Problems are due on the day of the Unit Test on a separate piece of paper. The Unit Test will be on: _____________________
Core Topics
Essential Knowledge
Practice from HOLT Chemistry
Topic 1:
Atoms are made of three types of subatomic particles: protons, neutrons and
electrons. Each atom has a nucleus in the center, made of protons and neutrons
packed tightly together. An electron cloud surrounds the atomic nucleus.
Read pg 79-86 – Subatomic
Particles
Elements and the Periodic
Table
A proton has a positive charge and a relative mass of one. The atomic number
for an element is the same as the number of protons. All atoms of the same
element have the same number of protons.
An electron has a negative charge and a relative mass of zero. The number of
electrons is the same as the number of protons in a neutral atom.
Read pg 84 – Atomic Number is the
Number of Protons of the Nucleus
Do pg 86 – Practice Problems
#1-4
A neutron has no charge and a relative mass of one.
Topic 2:
Compounds and Bonding
Subscripts in a chemical formula represent the relative number of each type of
atom. The subscript always follows the symbol for the element. The subscripts
indicate the ratio elements (in terms of atoms or moles) in the compound.
Parentheses are used when a subscript affects a group of atoms.
Example: the formula for magnesium nitrate is written Mg(NO3)2 to show that
there is a ratio of one magnesium atom, 2 nitrogen atoms and 6 oxygen atoms in
the compound.
Topic 3:
Kinetic Theory
Solids have a fixed shape. In a solid the particles are closely packed together.
Each particle in a solid is held in one position and vibrates around that position.
This results in a definite shape and volume.
Read pg 24 – Compounds are
Represented by Formulas
Read pg 236 – Formulas Express
Composition
Read pg 378 – 380 – States of
Matter
The particles in a liquid stay relatively close together, but they can move
around each other (rotate or tumble). This results in a definite volume but no
definite shape.
Gas particles are far apart; they move rapidly and collide with each other and
with the walls of the container. This random motion results in no definite shape
or volume.
Topic 4:
The Mole and
Stoichiometry
Phase changes (changes in physical state) occur when particles either speed up
or slow down changing their relative motions. For a given substance, freezing
and melting occur at the same temperature. Boiling and condensing also occur at
the same temperature. For example, water both freezes and melts at 0oC (and
both boils and condenses at 100 oC). Which phase change takes place depends on
whether heat (energy) is being added or removed.
Isotopes are atoms of the same element that have different numbers of
neutrons. Some isotopes are radioactive, many are not
Mass number of an individual isotope is the sum of the # of protons and the
# of neutrons in an atom of that isotope.
An element’s atomic mass, located on the Periodic Table, is a weighted average
of the masses of all the known isotopes of the element.
An element’s atomic mass represents the mass of one mole (6.02 x 1023
atoms) of the element and is called its molar mass. Be able to determine the
number of moles for a given mass of an element.
Topic 5:
Chemical Reactions
The chemical reaction where elements react (bond together) to form a
compound is called synthesis. Example: Hydrogen gas and oxygen gas react to
synthesize water. 2H2 + O2  2H2O
The elements in a compound can only be separated by a chemical reaction. This
reaction breaks the bonds between the elements resulting in decomposition.
(Example: water decomposes to form hydrogen and oxygen gas.
2H2O  2H2 + O2
In both reactions, the rearrangement of atoms results in chemical bonds being
broken and formed.
Bond breaking requires energy while bond making releases energy
Read pg 382 – 383 (Note the key
terms highlighted)
Do pg 384 – Problems # 1, 4, 6,
11, & 15.
Read pg 84 – Mass Number is the
Number of Particles in the Nucleus
Read pg 88 – Isotopes of an
Element Have the Same Atomic
Number
Read pg 230 – Amount in Moles Can
Be Converted to Mass
Do pg 89 – Problems # 1, 2, & 5
Read pg 277-278 – Synthesis
Reactions
Read pg 278-279 – Decomposition
Reactions
Topic 6:
Solutions
Topic 7:
A solution is a homogeneous mixture because the separate parts of the mixture
are distributed evenly and cannot be seen. The solvent (usually water) is the
part of the solution that is present in largest amount. The solute is the
substance that is dissolved in the solvent.
Read pg 455 – Solutions are Stable
Homogenous Mixtures
Read pg 455 – Solution is a Broad
Term
A saturated solution has all the dissolved solute that it can hold, and can be
identified by undissolved solute particles on the bottom after mixing. An
unsaturated solution can still hold more solute.
Read pg 474 – Saturation
Identify equipment: ring stand, funnel, watch glass, beaker, graduated cylinder
and evaporating dish.
Read pg 17 – Density Can be Used to
Identify Substances
Demonstrate filtration and evaporation and explain when each can be used to
physically separate a mixture. Define filtrate as the liquid that passes through
the filter.
Do pg 31 – Problem # 8
Do pg 477 – Problem # 7
Experimentation
Measure volume of a liquid in milliliters (mL) using a graduated cylinder and
stating measured digits plus the estimated digit. Be sure to read the bottom of
the meniscus of the liquid.
Measure mass in grams (g) using an electronic balance and identifying the
estimated digit.
Determine the density of solids and liquids experimentally and with the proper
number of significant digits.
When multiplying and dividing the least number of significant figures is the
number you use in your answer.