8th Grade Science

Directed Reading Packet

Chemistry

Name: ___________________________

Teacher: _____________ Period: _____

Chapter 1, Section 1: Inside the Atom

Introduction

1. Atoms are the ________________ particles of an element that still have the element’s

______________.

2. How many atoms would fit at the period at the end of the previous sentence?

Parts of the Atom

Nucleus

3. What are the two particles contained in the nucleus?

4. This is a very tiny part of the atom, but contains most of the atom’s _____________

5. Explain how the size of the nucleus compares to the size of the entire atom?

Protons

6. The proton is the part of the nucleus with a _______________ charge.

7. The number of protons is unique and gives each element their chemical ___________________

8. Can different elements ever have the same number of protons?

Neutrons

9. Where are neutrons found?

10. What is the charge of a neutron?

Electrons

11. Where can electrons be found? ___________________________________

12. All electrons have a ___________________ charge.

13. The number electrons usually equal the number of ____________________.

14. Fill in the chart below:

Subatomic Particle Electrical Charge Location in Atom

proton in nucleus

electron negative

neutron

Atomic Number and Mass Number

15. ______________________ have almost no mass.

16. Where is the majority of the mass of an atom located? ___________________

17. The SI unit for the mass of the atom is the _______________________________ otherwise known as

the AMU.

18. Electrons basically have a mass of zero, but protons and neutrons both have an individual mass of

_________ AMU’s.

19. What is the atomic number of an atom?

20. What is the atomic mass of an atom?

21. If an atom has an atomic number of 10 and a mass number of 22, how many protons, neutrons, and

electrons does this atom have?

Lesson Summary

The nucleus is at the center of an ___________. It contains _____________ protons and ____________

neutrons. ________________ electrons constantly move about the ________________.

Atomic _____________ is the number of ___________________ in an atom. It is unique for the atoms of

each ___________________. _____________ number is the number of __________________ plus

__________________ in an atom. It is about __________________ to the mass of the atom in

__________________ mass units (AMU).

Chapter 1, Section 2: Modern Atomic Theory

Introduction

1. Who were the two major scientists involved in the development of atomic model theory?

Bohr Model of the Atom

2. The Bohr model of the atom became the widely accepted explanation of what an atom looks like. Please

draw the Bohr model with the nucleus and three energy levels labelled below.

What Are Energy Levels?

3. Energy levels (AKA: Energy __________ ) are ______________ distances from the nucleus and are where

_____________ are found.

4. How are energy levels like steps of a staircase?

5. Draw an arrow indicating the energy level with the highest energy and the energy level with the lowest

energy.

6. Explain how electrons can jump from a lower energy level to a higher energy level.

7. Explain how electrons can jump from a higher energy level to a lower energy level.

8. Explain an example of electrons jumping up and down energy levels?

9. In the Bohr model each energy level can hold a maximum number of electrons. How many electrons can

be held in each level?

a. Energy Level 1: _______________

b. Energy Level 2: _______________

c. Energy Level 3: _______________

10. Compare how electrons will fill energy levels to people filling in the rows in our auditorium for an

assembly. (Include, which rows fill first, and how each rows fills)

The Outermost Level

11. Define valence electrons:

12. Why are valence electrons so important?

13. When are atoms most stable?

14. Draw the Bohr model for the element Carbon. (Reference the model in number 5 for help.)

Lesson Summary

Bohr introduced the idea that _________________ orbit the _____________ at fixed distances, called

___________ ___________. Electrons in energy levels farther from the nucleus have more __________

Today, electrons are represented by an electron __________ model. Orbitals in the cloud show where

_____________ are most likely to be located.

Chapter 2, Section 1: How Elements Are Organized

Introduction

1. What is the full name of the scientist who organized the elements into a periodic table?

Mendeleev’s Periodic Table of Elements

2. When arranging the elements Mendeleev made cards with three things listed on them? What are the

three things he listed on the cards?

A Repeating Pattern

3. Elements are arranged from left to right by _________________ ______________ _________.

4. The elements in the same column all had similar __________________.

5. These columns were called ________________ or ________________.

6. The rows of the table are called ________________ because they have a specific interval of repetitions.

Predicting Missing Elements

7. Using the periodic table and the patterns Mendeleev and others filled in all the blanks in the periodic

table. What was the first missing element Mendeleev predicted?

The Modern Periodic Table of Elements

Basis of the Modern Periodic Table

8. The modern periodic table is organized by __________________ ________________, not by

________________ _________.

9. Why did Mendeleev not use atomic number to organize his table?

Reading the Table

10. For the periodic table in figure 2.3 list all the characteristics for calcium.

Periods

11. Periods of the modern periodic table are also known as _____________ and are read from __________

to ____________.

12. On the left side of the charge are the ____________, followed by the ________________ in the middle

of the chart, and the ________________ on the right side.

13. What increases by one every element as you read from left to right?

Groups

14. In the modern periodic table the elements that are in a vertical column are called _______________.

15. How many groups are in the current periodic table?

16. Elements in the same group have similar ____________________.

17. In the periodic table below what is the atomic number for Jk?

18. What is the atomic mass for Jk?

19. What two elements are most similar to Jk?

Lesson Summary

Mendeleev developed the first periodic table of the elements in __________. He organized the elements

by _______________ atomic mass. He used the table to ______________ unknown elements. These

were later discovered.

The modern periodic table is based on ___________ ___________. Elements in each _____________ go

from metals on the ____________ to metalloids and then nonmetals on the ___________. Within

____________, elements have similar properties.

Chapter 2, Section 2: Classes of Elements

Introduction

1. What are the three classes of elements?

Metals

2. List 5 characteristics of metals

3. What are some commons uses of metals?

Nonmetals

4. Where are nonmetals located on the periodic table of elements?

5. List 5 characteristics of nonmetals.

6. What are some commons uses of nonmetals?

Metalloids

7. How many elements are considered metalloids?

8. In your own words define what a metalloid is?

Classes of Elements and Electrons

Electrons by Class

9. Which energy level gets electrons first?

Valence Electrons and Reactivity

10. Define valence electrons?

11. Which class of elements have low numbers of valence electrons and want to give them away (react) and

can conduct electricity? ____________________________

12. Why would lithium give away its valence electrons?

13. Which class of elements have high numbers of valence electrons and want to gain electrons (react) and

do not conduct electricity? ________________________________

14. Why would chlorine take in more valence electrons?

15. What happens when your outer shell of valence electrons is filled?

Lesson Summary

Metals are elements that are good ____________ of electricity. They are the ____________ class of

elements. Many metals are ___________, _____________ and ______________. They are also good

conductors of _________. Almost all metals are ____________ at room temperature.

Nonmetals are elements that do _______ conduct electricity. They are the _____________ largest class

of elements. Nonmetals are __________ conductors of heat. The majority of nonmetals are __________.

Solid nonmetals are _________ and ______________.

Metalloids are elements that have properties of both _________________ and ___________________.

Some can conduct _______________, but only at certain __________________. They may be shiny, but

____________. All metalloids are _______________ at room temperature.

Atoms of elements in different classes vary in their number of _________________ ________________.

This explains their differences in __________________ and ______________________.

Chapter 3, Section 1: Introduction to Chemical Bonds

Introduction

1. When elements combine together they are called _______________________

Chemical Bonding

2. How is a chemical bond formed?

3. When bonding, valence electrons (those in the outermost energy level) can either be ________________

or __________________.

Chemical Compounds

4. Because all chemical compounds consist of a ________________ ratio of elements, water will always

have ___________ hydrogen and _________ oxygen.

Chemical Formulas

5. The chemical formula for water is H2O. What does the subscript 2 after H mean?

6. In the chemical formula for water there is no number subscript written after O. What does that mean?

7. In the chemical formula for glucose CH2O how many of each element are there.

Same Elements, Different Compounds

8. Listed below are two chemical formulas both containing Hydrogen (H) and Oxygen (O). Explain why the

two chemical formulas below are different compounds

H2O H2O2

Types of Compounds

9. List the three different types of chemical bonds?

Lesson Summary

A chemical bond is a force of __________________ between atoms. It occurs when atoms

_____________ or _______________ electrons.

A chemical _________________ is a new substance that forms when atoms of _______________

elements forms chemical bonds. A compound always consists of a ____________ ratio of elements.

Chapter 3, Section 2: Ionic Bonds

Introduction

1. Explain how an ionic bonds forms. (Be specific with what happens to the electrons.)

Ions

2. Ions form when an atom _________________ or ______________ electrons.

3. If an atom loses an electron it becomes ____________________ charged, also called a ______________

4. If an atom gains an electron it becomes ____________________ charged, also called a ______________

5. Do you think the atom below will form a positive or negative ion? Explain below.

Isotopes of Atoms

6. Atoms that have a different number of neutrons, but the same number of protons are ______________.

7. Different isotopes of the same elements generally have the ________________ chemical properties.

8. How many different isotopes of Hydrogen are there? List them and explain the differences.

Formation of Ionic Bonds

9. What happens when a positive and negative ion get near each other?

10. All ionic bonds are formed between _______________, positive ions, and ____________________,

negative ions.

11. When bonding occurs metals always ___________ electrons, and nonmetals always ____________

electrons.

12. Explain, in writing, how Sodium (Na) and Chlorine (Cl) bond ionically.

13. Show with atomic model diagrams and arrows how Sodium and Chlorine bond ionically.

Why Ionic Bonds Form

14. Explain why an element in group 1 likes to bond with an element in group 17.

15. When sodium loses its one electron, it will have a __________ outer energy level.

Energy and Ionic Bonds

16. It takes ______________ to remove valence electrons during ionic bonding. ____________ energy is

needed to remove a small number of electrons. ___________ energy is needed to break free a

_____________ number of electrons.

17. Atoms that _____________ electrons gain energy, and atoms that ___________ electrons lost energy.

Properties of Ionic Compounds

18. The negative ion to positive ion attraction in ionic bonds creates a strong and rigid___________ lattice

and it takes _____________ amounts of energy to break these bond.

19. List 4 properties or characteristics of ionic compounds.

Uses of Ionic Compounds

20. Explain one way in which the human body needs ions.

Lesson Summary

If atoms lose or gain ____________, they become _______________ or _______________ ions. Atoms

of the same element that have ________________ numbers of _______________ are called

________________.

An ______________ bond is the force of _________________ that holds together oppositely charged

ions. It forms when atoms of a _____________ transfer electrons to atoms of a __________________.

When this happens, the atoms become ______________________ charged ions.

Ionic compounds form ________________ instead of molecules. Ionic bonds are ________________

and the crystals are _____________. As a results, ionic compounds are _____________ solids with high

_____________ and _________________ points. In the ________________ state or dissolved in water,

ionic compounds are good conductors of ____________________.

Chapter 3, Section 3: Covalent Bonds

Formation of Covalent Bonds

1. What is a covalent bond?

2. All covalent bonds are only between a _______________ and a ___________________.

Why Covalent Bonds Form

3. Why do covalent bonds form?

4. The shared electrons are attracted to the nuclei of ___________ atoms in the bond.

5. Water is an example of a simple covalently bonded molecule. Fill in the electrons on the sketch of the

water molecule. Show where the electrons are shared.

H H

O

6. How many valence electrons does the oxygen atoms share with each hydrogen atom?

7. How many covalent bonds hold the water molecule together?

8. Try to draw a sketch showing the electrons of a covalent bonded molecule of HCl

Covalent Compounds

9. A __________________ is two or more nonmetals bonded together covalently. An example is _______.

10. List the three rules in names a simple covalent compound.

Properties of Covalent Compounds

11. Because covalent compounds share electrons and make molecules they have different properties. List

five characteristics or properties of covalent compounds.

12. What is a hydrogen bond?

13. Draw out an example of a hydrogen bond between water molecules.

Lesson Summary

A covalent bond is the force of _________________ that holds together two atoms that ___________ a

pair of electrons. It forms between atoms of the same or different _________________. In polar

covalent bonds, one atom attracts the _______________ electrons more strongly and becomes slightly

______________. The other atoms becomes slightly _________________.

Covalent compounds form individual _______________ rather than __________________. Compared

with ionic compounds, they have ___________ melting and boiling points. They are also _____________

conductors of electricity.

Chapter 3, Section 4: Metallic Bonds

Formation of Metallic Bonds

1. Explain the “Sea of Electrons” in metallic bonding.

2. All metallic bonds are formed between a ______________ and a _______________.

Metallic Bonds and the Properties of Metals

3. The “Sea of Electrons,” that allow free movement of electrons, allows metals to be _____________

conductors of electricity.

4. What is the difference between metals that are ductile and metals that are malleable?

5. Can metals be both ductile and malleable?

6. Explain how a blacksmith or metal worker can hammer metals into shapes they want without the metal

shattering.

Lesson Summary

A metallic bond is the force of attraction between a _________________ charged metal ion and the

________________ electrons it share with other _________ of the metal. The _________________

move freely around the positive ions, which form a ________________________ structure.

With _________________ moving electrons, metals are _____________ conductors of electricity. The

______________ ions of metals can also move within the “sea” of ________________ without

breaking the metallic bonds that hold them together. This allows metals to change ______________

without breaking.

Chapter 4, Section 1: Introductions to Chemical Reactions

Introduction

1. What happens in a chemical change?

What is a Chemical Reaction?

2. What is a chemical reaction?

3. The substances you start with are _________________ and the substances that are produced and you

end with are ________________.

4. Draw a representation of a chemical reaction and explain what the arrow means.

Breaking and Reforming Chemical Bonds

5. There are three basic steps in a chemical reaction. List them below in order.

Reaction Direction and Equilibrium

6. When the forward and reverse reactions occur at the same rate the reaction has reached ____________.

Evidence of Chemical Reactions

7. List the four commons signs that a chemical reaction has occurred.

8. Circle the chemical reactions from the choices below:

Photosynthesis Water Freezing Leaves changing colors Baking Soda and Vinegar

Lesson Summary

A chemical reaction is a process in which some _________________ change into _______________

substances. In a chemical reaction, bonds _____________ in reactants and new bonds form in

_________________.

Evidence that a chemical reaction has occurred include a change in ______________, a change in

____________________, the production of a ___________, or the formation of a __________________.

Chapter 4, Section 2: Chemical Equations

Writing Chemical Equations

1. In this equation, from the flexbook, list the reactants and the products

C + O2 CO2

2. In the previous reaction how many carbon atoms are on the reactant side? Oxygen atoms?

3. Are those numbers the same as the number of atoms on the product side?

4. A chemical equation represents changes that occur during a chemical _________________.

Balancing Chemical Equations

5. Look at the following equation: H2 + O2 H2O

What is wrong with the way this chemical equation is written?

Using Coefficients

6. Coefficients are used to ______________________ chemical equations. Coefficients show how many

_______________ or _______________ of a substance are involved in the reaction.

7. Circle the coefficients in the following equations:

CH4 + 2O2 CO2 + 2H2O

2H + CO3 H2O + CO2

CaCl + 2AgNO Ca(NO3)2 + 2AgCl

Steps in Balancing a Chemical Equation

8. When you balance equations, _______________ change the subscripts in chemical formulas.

9. If you change the subscript you will change the _________________ involved in the reaction, only

change the _______________________.

10. Try to balance the following chemical equations by adding coefficients in the spaces provided. If you need help refer to some of the practice problems in the flexbook.

___H2 + ___O2 ___H2O ___N2 + ___H2 ___NH3

___Zn + ___HCl ___ZnCl2 + ___H2

Conserving Mass

11. Why must chemical equations be balanced?

12. What is the Law of Conservation of Mass?

13. In what century did Antoine Lavoisier run experiments to show mass conservation?

14. How was Lavoisier able to prove the Law of Conservation of Mass?

15. What secondary discovery did Lavoisier discover from his experiments?

Lesson Summary

A chemical ___________________ is a symbolic representation of a chemical _________________. It

shows how __________ are _____________________ in the reaction.

Equations in chemistry must _________________. There must be the same number of each type of

____________ in the ___________________ as there is in the _____________________. Coefficients are

used to ___________________ chemical equations. They show how many ______________ or

_________________ of a substance are involved in a reaction.

Chemical equations must be _____________________ because matter cannot be

___________________ or ___________________. This is the law of _________________________ of

mass. Experiments by Antoine Lavoisier led to this law.

Chapter 4, Section 3: Types of Chemical Reactions

Introduction

1. List the four common types of chemical reactions.

a.

b.

c.

d.

2. Which type of reaction is most often seen?

Synthesis Reactions

3. Write out the general equation for a synthesis reaction.

4. Explain what happens in a synthesis reaction and write out one example.

Decomposition Reactions

5. Write out the general equation for a decomposition reaction.

6. Explain what happens in a decomposition reaction and write out one example.

Replacement Reactions

7. Replacement reactions involve __________ and there are _________ types of replacement reactions.

8. Ions ____________ places in compounds so they are in different places in the products than they were in

the reactants

Single Replacement Reactions

9. Write out the general equation for a single replacement reaction and give an example.

Double Replacement Reactions

10. Write out the general equation for a double replacement reaction and give an example.

Combustion Reactions

11. Combustion reactions is when a substance reacts rapidly with ________________.

12. The final products of a combustion reaction are always ______________ and ______________.

13. Write out the general equation for a combustion reaction and show an example.

Lesson Summary

A ___________________ reaction occurs when ______________ or more reactants _________________

to forms a single ________________

In a decomposition reaction, one _______________ breaks down into ___________ or more

_______________. This is the ___________________ of a synthesis reaction.

Replacement reactions occur when elements __________________ places in compounds. In a

_________________ replacement reaction, one ________________ takes the place of another in a

single ________________. In a __________________ replacement reaction, _________________

compounds ___________________ elements.

A combustion reaction occurs when a substance reacts quickly with ___________________. Combustion

is commonly called _________________. Carbon Dioxide, ________________, and heat and light are

products of combustion.

Chapter 4, Section 4: Chemical Reactions and Energy

Introduction

1. During a chemical reaction, _______________ is used to break bonds in reactants, and ______________

is released when new bonds form in the products.

Endothermic Reactions

1. Exothermic reactions take more _______________ to break bonds in _________________ than is

released when new bonds form in the __________________.

2. Write out the general equation for an endothermic reaction. _________________________________

3. A ________________ input of energy is required in endothermic reactions usually in the form of

__________, absorbed from surroundings.

4. The absorption of _____________ causes the temperature around the reactants to _____________.

5. ________________________ is an example of an endothermic reaction.

Exothermic Reactions

6. Exothermic reactions take ____________ energy to break bonds in the ____________ than is released

when new bonds form in the ________________.

7. Write out the general equation for an exothermic reaction. ___________________________________

8. When the energy released is ___________, the temperature in the surrounding environment _________.

9. Examples of energy given off include: ________________, ______________ and possibly sound.

Conservation of Energy

10. What is the Law of Conservation of Energy?

11. Fill in the missing boxes with the correct terms for the following reactions.

Activation Energy

12. Activation Energy is the energy required to _______________ a reaction.

13. The activation energy creates the required _________________ needed for the reactants to collide.

Reaction Rates

14. List the four factors that influence the rates, speed, of a chemical reaction

a.

b.

c.

d.

Temperature of Reactants

15. When the temperature of the reactants is higher, the rate of the reaction is _______________. 16. Why do reactions happen faster at higher temperatures?

Concentration of Reactants

17. When the concentration of reactants is higher, the rate of the reaction is _______________. 18. Why do reactions happen faster with higher concentrations of reactants?

Surface Area of Reactants

19. Increasing the surface area of reactants, _______________ the reaction rate? 20. Why do reactions happen faster when reactants have a greater surface area?

Presence of a Catalyst

21. A catalyst is a substance that _______________ the rate of a chemical reaction. 22. Catalysts are not ______________ and are not used up in a reaction.

Lesson Summary

In an _______________________ reaction, it takes more _______________ to break bonds in the

reactants than is _________________ when new bonds form in the products. Therefore, an endothermic

reaction needs a __________________ input of _________________ to keep going.

In an exothermic reaction, it takes __________________ energy to break ______________ in the

reactants than is released when new bonds form in the ____________________. Therefore, an

___________________ reaction releases enough energy to keep going.

In any chemical reaction, there is no ________________ change in the amount of _________________.

Energy cannot be ____________________ or _________________________. This is the law of

________________________ of energy.

All chemical reactions, even ______________________ reactions, need __________________ energy to

get started. Activation energy is needed to bring _______________________ together so they can react.

How fast a reaction occurs is called the ___________________ ______________. Factors that affect the

reaction rate include _____________________ and the _______________________,

_______________________, and ______________________ area of reactants. A ___________________

is a substance that ______________________ the rate of a chemical reaction but it not changed or used

up in the reaction.