REFERENCES

WORKBOOK
Science 8

TOPICS
Learning Outcome 1: Ecosystems
REFERENCES
Topic 1.1: Photosynthesis
Topic 1.2: Cellular Respiration
Learning Outcome 2: Matter
Topic 2.1: What is Matter?
Topic 2.2: Structure of Atom
Topic 2.3: Elements and Compounds
Learning Outcome 3: Ties that Bind
Topic 3.1: Valence Electron
Topic 3.2: Lewis Dot Structures of Representative
Element

LEARNING OBJECTIVES
At the end of this workbook, the learners are expected to:
 Explain the role of energy in life processes;
 Identify the importance of raw materials;
 Describe the two photosynthetic reactions in plants;
 Explain the role of ATP in life processes;
 Trace the major events of glycolysis and aerobic respiration;
 define matter;
 determine the structure of an atom;
 differentiate between elements and compounds
 define valence electron;
 determine the number of valence electrons in an atom based on
its position in the periodic table; and
 draw electron-dot structures of representative elements.

MATERIALS
Pen
Answer sheet
Periodic Table

. Pavico, A.Ramos, A. Bayquen, A. Silverio, J. Ramos, Exploring Life through

Science Series The New Grade 9, Phoenix Publishing House

1|Page
 DEFINITION OF TERMS
Adenosine Triphosphate (ATP) : compound that stores energy
in the cell
Autotrophs : organisms that can make their own
food.
Calvin Cycle : name given to the cycle of dark reaction in
photosynthesis
Cellular Respiration : catabolic process pathways of aerobic and
Anaerobic
respiration, which break down
organic
molecules for the production of ATP.
Chlorophyll : green pigment in the chloroplast of
photosynthetic
organisms that
captures light
energy
Chloroplast : organelle found in photosynthetic
organisms
that absorb
sunlight and use it to synthesize
carbon dioxide

Learning Outcome 1: Ecosystem

WHAT DO YOU NEED TO KNOW?

Before proceeding to the topics, you’re about to study, answer the following
questions.
A. How do plants manufacture their own food?
_______________________________________________________________________________
_______________________________________________________________________________
B. What are the factors that affect the rate of photosynthesis?
_______________________________________________________________________________
_______________________________________________________________________________
C. How do cells convert stored energy in food into chemical energy?
_______________________________________________________________________________
_______________________________________________________________________________
D. How do materials and energy flow in the ecosystem?
_______________________________________________________________________________
_______________________________________________________________________________
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Photosynthesis: Using Light Energy to
Produce Food
Photosynthesis is a process of
food making done by plants and other
autotrophic organisms. The presence of
chlorophyll enables these organisms to
make their own food. Autotrophic
organisms require light energy, carbon
dioxide (CO2), and water (H2O) to make
food (sugar).

Leaves: Specialized Organs for

Photosynthesis
The typical parts of the leaves include the upper and lower
epidermis, mesophyll spongy layer, vascular bundles, and stomates. The
upper and lower epidermis protects the leaves and has nothing to do
with photosynthetic processes. Mesophyll has the greatest number of
chloroplasts that contain chlorophyll. They are important in trapping light
energy from the sun. Vascular bundles - phloem and xylem serve as
transporting vessels of manufactured food and water. Carbon dioxide and
oxygen were collected in the spongy layer and enters and exits the leaf
through the stomata.
The parts of a chloroplast
include the outer and inner
membranes, intermembrane space,
stroma and thylakoids stacked in
grana. The chlorophyll is built into
the membranes of the thylakoids.
Chlorophyll absorbs white light but it
looks green because white light
consists of three primary colors: red,
blue, and green. Only red and blue
light is absorbed thus making these colors unavailable to be seen by our
eyes while the green light is reflected which makes the chlorophyll looks
green. However, it is the energy from red light and blue light that are
absorbed and will be used in photosynthesis. The green light that we can
see is not absorbed by the plant and thus, cannot be used in
photosynthesis.
Photosynthesis: Food Making Process in
Plants
1. Light-Dependent Stage
Light-dependent reaction happens in the
presence of light. It occurs in the thylakoid
membrane and converts light energy to
chemical energy. Water-one of the raw
materials of photosynthesis-is utilized during

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this stage and facilitates the formation
of free electrons and oxygen. The
energy harvested during this stage is
stored in the form of ATP (Adenosine
Triphosphate) and NADPH(Nicotinamide
Adenine Dinucleotide Phosphate
Hydrogen). These products will be
needed in the next stage to complete
photosynthetic process.
2. Light-Independent Stage
Calvin Cycle (dark reaction)
is a light-independent phase that takes
place in the stroma and converts Carbon dioxide (CO2) into sugar. This
stage does not directly need light but needs the products of light reaction.
This is why it occurs immediately after the light-dependent phase
Direction: Label the parts of a chloroplast and the internal structure of a
leaf. Write your answer in the box.

Internal Structure of
Leaves

Chloroplast

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Cellular Respiration
All heterotrophic organisms including man, depend directly or
indirectly on plants and other photosynthetic organisms for food. Why do
we need food? Organisms need food as the main source of energy. All
organisms need energy to perform essential life processes. The food must
be digested to simple forms such as glucose,
amino acids, and triglycerides. These are then
transported to the cells. The immediate energy
source of the cells is glucose. Glucose inside the
cell is broken down to release the stored
energy. This stored energy is harvested in the
form of adenosine triphosphate (ATP). ATP is a
high-energy molecule needed by working cells.
Glycolysis
In glycolysis, the 6-carbon sugar,
glucose, is broken down into two molecules of a
3-carbon molecule called pyruvate. This change
is accompanied by a net gain of 2 ATP
molecules and 2 NADH molecules.
Krebs Cycle
The Krebs Cycle occurs in the
mitochondrial matrix and generates a
pool of
chemical energy (ATP, NADH, and
FADH2) from the oxidation of pyruvate,
the end product of glycolysis. Pyruvate is
transported into the mitochondria and
loses carbon dioxide to form acetyl-CoA,
a 2-carbon molecule. When acetyl-CoA is
oxidized to carbon dioxide
in the Krebs cycle, chemical energy is
released and captured in the form of NADH, FADH2, and ATP.
Electron Transport Chain
The electron transport chain allows the release of the large
amount of chemical energy stored in reduced NAD+ (NADH) and reduced
FAD (FADH2). The energy released is captured in the form of ATP (3ATP
per NADH and 2 ATP per FADH2).
Electron transport chain consists of series of molecules, mostly
proteins, embedded in the inner mitochondrial membrane.
This phase of cellular respiration produces the greatest number of
chemical energies in the form of ATP.

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 DIGGING DEEPER

Direction: Answer the following questions and refer to the diagram above.

Q1. Which of the terms found in the diagram is considered a process?

_______________________________________________________
Q2. In which part of the cell does the process take place?
________________________________________________________
Q3. What is the raw material?
________________________________________________________
Q4. What are the products?
_________________________________________________________

A. Answer the following questions.

1. How important is solar energy to you?
___________________________________________________________________________
___________________________________________________________________________
2. How do you get energy from food?
___________________________________________________________________________
___________________________________________________________________________
3. Oxygen is essential in cellular respiration. What is the role of oxygen in
the electron transport chain?
___________________________________________________________________________
___________________________________________________________________________

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 4. What will happen if ATP and NADPH are already used up at night?
___________________________________________________________________________
___________________________________________________________________________
5.What is the Outcome of Glycolysis?
___________________________________________________________________________
___________________________________________________________________________

Learning Outcome 2: Matter

WHAT DO YOU NEED TO KNOW?

Before proceeding to the topics, you’re about to study, answer the following
questions.
1. Describe matter
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
2. Do you think atom and element are similar? Explain.
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
3. Do you think matter is anywhere around us? Explain.
_______________________________________________________________________________
_______________________________________________________________________________
4. What do you think is the difference between elements and compounds?
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
5. Do you think matter is important? Explain.
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
What is your body made of?

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 Your first thought might be that it is made up of different organs—
such as your heart, lungs, and stomach—that work together to keep your
body going. Or you might zoom in a level and say that your body is made
up of many different types of cells. However, at the most basic level, your
body—and, in fact, all of life, as well as the nonliving world—is made up of
atoms, often organized into larger structures called molecules.
Matter
The term matter refers to anything that occupies space and has mass—in
other words, the “stuff” that the universe is made of. All matter is made
up of substances called elements, which have specific chemical and
physical properties and cannot be broken down into other substances
through ordinary chemical reactions. Gold, for instance, is an element,
and so is carbon. There are 118 elements, but only 92 occur naturally. The
remaining elements have only been made in laboratories and are
unstable.
Each element is designated by its chemical symbol, which is a single
capital letter or, when the first letter is already “taken” by another
element, a combination of two letters. Some elements follow the English
term for the element, such as C for carbon and Ca for calcium. Other
elements’ chemical symbols come from their Latin names; for example,
the symbol for sodium is Na, which is a short form of natrium, the Latin
word for sodium.
The four elements common to all living organisms are oxygen (O),
carbon (C), hydrogen (H), and nitrogen (N), which together make up about
96% of the human body. In the nonliving world, elements are found in
different proportions, and some elements common to living organisms are
relatively rare on the earth as a whole. All elements and the chemical
reactions between them obey the same chemical and physical laws,
regardless of whether they are a part of the living or nonliving world.

Direction: Determine the names of the following

element symbol.
Element Symbols Elements Name
1. Na

2. K

3. Ar

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4. He
5. Li

6. Be
7. N
8. O
9. F
10. Cl

The structure of the atom

An atom is the smallest unit of matter that retains all of the
chemical properties of an element. For example, a gold coin is simply a
very large number of gold atoms molded into the shape of a coin, with
small amounts of other, contaminating elements. Gold atoms cannot be
broken down into anything smaller while still retaining the properties of
gold. A gold atom gets its properties from the tiny subatomic particles it's
made up of.

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 An atom consists of two regions.
The first is the tiny atomic nucleus,
which is in the center of the atom and
contains positively charged particles
called protons and neutral, uncharged,
particles called neutrons. The second,
much larger, region of the atom is a
“cloud” of electrons, negatively charged
particles that orbit around the nucleus.
The attraction between the positively charged protons and negatively
charged electrons holds the atom together. Most atoms contain all three
of these types of subatomic particles—protons, electrons, and
neutrons. Hydrogen (H) is an exception because it typically has one
proton and one electron, but no neutrons. The number of protons in the
nucleus determines which element an atom is, while the number of
electrons surrounding the nucleus determines which kind of reactions the
atom will undergo. The three types of subatomic particles are illustrated
below for an atom of helium—which, by definition, contains two protons.
Protons and neutrons do not have the same charge, but they do
have approximately the same mass, about 1.67 × 10 -24 grams. Since
grams are not a very convenient unit for measuring masses that tiny,
scientists chose to define an alternative measure, the Dalton or atomic
mass unit (amu). A single neutron or proton has a weight very close to 1
amu. Electrons are much smaller in mass than protons, only about 1/1800
of an atomic mass unit, so they do not contribute much to an element’s
overall atomic mass. On the other hand, electrons do greatly affect an
atom’s charge, as each electron has a negative charge equal to the
positive charge of a proton. In uncharged, neutral atoms, the number of
electrons orbiting the nucleus is equal to the number of protons inside the
nucleus. The positive and negative charges cancel out, leading to an atom
with no net charge.
Protons, neutrons, and electrons are very small, and most of the
volume of an atom—greater than 99 percent—is actually empty space.
With all this empty space, you might ask why so-called solid objects don’t
just pass through one another. The answer is that the negatively charged
electron clouds of the atoms will repel each other if they get too close
together, resulting in our perception of solidity.

Direction: Complete the table.

Atom Numb Numbe Number of
Mass
Symb ic er of r of electrons
Elements Num
ol Num Proto Neutro
ber
ber ns ns

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 1) Helium 2

2) Magnesium 12 12

3) Zinc 30 65

4) Bromine 80 35

5) Aluminum 13 14

6) Uranium 92

7) Sodium 11 12

8) Hydrogen 1 1

9) Calcium 40 20

10) Silver 47 61

Elements
A chemical element is a
pure substance that consists of
one type of atom. Each atom has
an atomic number, which
represents the number of protons
that are in the nucleus of a single
atom of that element. The
periodic table of elements is
ordered by ascending atomic
number.
The chemical elements are divided into the metals, the metalloids,
and the non-metals. Metals, typically found on the left side of the periodic
table, are:
⮚ often conductive to
electricity
⮚ malleable
⮚ shiny
⮚ sometimes magnetic.

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 ⮚ Aluminum, iron, copper, gold, mercury and lead are metals.
In contrast, non-metals, found on the right side of the periodic table (to
the right of the staircase), are:
⮚ typically, not conductive
⮚ not malleable
⮚ dull (not shiny)
⮚ not magnetic.
⮚ Examples of elemental non-metals include carbon and oxygen.
Metalloids have some characteristics of metals and some characteristics
of non-metals. Silicon and arsenic are metalloids.
As of November, 2011, 118 elements have been identified (the most
recently identified was ununseptium, in 2010). Of these 118 known
elements, only the first 98 are known to occur naturally on Earth. The
elements that do not occur naturally on Earth are the synthetic products
of man-made nuclear reactions. 80 of the 98 naturally-occurring elements
are stable; the rest are radioactive, which means they decay into lighter
elements over timescales ranging from fractions of a second to billions of
years.

The periodic table shows 118 elements, including metals (blue),

nonmetals (red), and metalloids (green).
Hydrogen and helium are by far the most abundant elements in the
universe. However, iron is the most abundant element (by mass) in the

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composition of the Earth, and oxygen is the most common element in the
layer that is the Earth’s crust.
Although all known chemical matter is composed of these elements,
chemical matter itself constitutes only about 15% of the matter in the
universe. The remainder is dark matter, a mysterious substance that is
not composed of chemical elements. Dark matter lacks protons, neutrons,
or electrons.
Compounds
Pure samples of isolated elements are uncommon in nature. While
the 98 naturally occurring, elements have all been identified in mineral
samples from the Earth’s crust, only a small minority of them can be
found as recognizable, relatively pure minerals. Among the more common
of such “native elements” are copper, silver, gold, and sulfur. Carbon is
also commonly found in the form of coal, graphite, and diamonds. The
noble gases (e.g., neon) and noble metals (e.g., mercury) can also be
found in their pure, non-bonded forms in nature. Still, most of these
elements are found in mixtures.
When two distinct elements are chemically combined—i.e., chemical
bonds form between their atoms—the result is called a chemical
compound. Most elements on Earth bond with other elements to form
chemical compounds, such as sodium (Na) and Chloride (Cl), which
combine to form table salt (NaCl). Water is another example of a chemical
compound. The two or more component elements of a compound can be
separated through chemical reactions.
Chemical compounds have a unique and defined structure, which
consists of a fixed ratio of atoms held together in a defined spatial
arrangement by chemical bonds. Chemical compounds can be:
⮚ molecular compounds held together by covalent bonds
⮚ salts held together by ionic bonds
⮚ intermetallic compounds held together by metallic bonds
⮚ complexes held together by coordinate covalent bonds.
Pure chemical elements are not considered chemical compounds,
even if they consist of diatomic or polyatomic molecules (molecules that
contain only multiple atoms of a single element, such as H 2 or S8.

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Part 1: Read the following information on elements and compounds . Fill
in the blanks where necessary.
Elements:
• A pure substance containing only one kind of ____________.
• An element is always uniform all the way through (homogeneous).
• An element _____________ be separated into simpler materials
(except during nuclear reactions).
• Over 100 existing elements are listed and classified on the
____________________.
Compounds:
• A pure substance containing two or more kinds of _______________.
• The atoms are _________________ combined in some way. Often
times (but not always) they come together to form groups of atoms called
molecules.
• A compound is always homogeneous (uniform).
• Compounds ___________________ be separated by physical means.
Separating a compound requires a chemical reaction.
• The properties of a compound are usually different than the
properties of the elements it contains.
Part 2: Classify each of the following as elements (E), compounds (C).
___(C) ___Sugar (C6H12O6) ___Iron (Fe)
___Sulfuric Acid (H2SO4) ___Krypton (K) ___Bismuth (Bi)
___Uranium (U) ___Water (H2O) ___Alcohol (CH3OH)
___Ammonia (NH3) ___Salt (NaCl) ___Gold (Au)
___Wood ___Dry Ice (CO2) ___Titanium (Ti)
___Baking Soda (NaHCO3) ___Concrete

Answer the following questions.

1.Name the three particles of the atom and their respective charges are:

14 | P a g e
 a. ___________________________ _______________________________

b.___________________________ _______________________________

c. ___________________________ _______________________________

2. The number of protons in one atom of an element determines the

atom’s _________________________, and the number of electrons determines
____________________ of an element.
3. The atomic number tells you the number of ____________________________
in one atom of an element. It also tells you the number of
____________________________ in a neutral atom of that element. The atomic
number gives the “identity “of an element as well as its location on the
Periodic Table. No two different elements will have the ___________________
atomic number.
4. Where is most of the mass of an atom located?
5. Define Matter

WHAT DO YOU NEED TO KNOW?

___________________________________________________________________________
___________________________________________________________________________
6. Give the difference Between Elements and Compounds.
___________________________________________________________________________
___________________________________________________________________________

Learning Outcome 2: Matter

Before proceeding to the topics, you’re about to study, answer the

following questions.
1. Do you think it is important to study about valence electrons?
Explain.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2. Do you believe that Lewis Electron-Dot Structure represents the real
positioning of valence electrons in an atom? Explain

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 _____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
3. How are valence electrons and group number reflected in electron
configurations?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
4. What is the standard pattern in representing the valence electrons
in the Lewis Dot Structure of the element?

Valence electrons and open valences

A valence electron is an electron that is associated with an atom,
and that can participate in the formation of a chemical bond; in a single
covalent bond, both atoms in the
bond contribute one valence electron
in order to form a shared pair. The
presence of valence electrons can
determine the element's chemical
properties and whether it may bond
with other elements: For a main
group element, a valence electron
can only be in the outermost electron
shell.
An atom with a closed shell of
valence electrons (corresponding to an electron configuration s 2p6 ) tends
to be chemically inert. An atom with one or two valence electrons more
than a closed shell is highly reactive, because the extra valence electrons
are easily removed to form a positive ion. An atom with one or two
valence electrons fewer than a closed shell is also highly reactive,
because of a tendency either to gain the missing valence electrons
(thereby forming a negative ion), or to share valence electrons (thereby
forming a covalent bond).
Like an electron in an inner shell, a valence electron has the ability
to absorb or release energy in the form of a photon. An energy gain can
trigger an electron to move (jump) to an outer shell; this is known as
atomic excitation. Or the electron can even break free from its associated
atom's valence shell; this is ionization to form a positive ion. When an
electron loses energy (thereby causing a photon to be emitted), then it
can move to an inner shell which is not fully occupied.
The number of valence electrons

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 The number of valence electrons of an element can be determined
by the periodic table group (vertical column) in which the element is
categorized. With the exception of groups 3–12 (the transition metals), the
units digit of the group number identifies how many valence electrons are
associated with a neutral atom of an element listed under that particular
column.

The periodic table of the chemical elements

* The general method for counting valence electrons is generally not
useful for transition metals. Instead the modified d electron count method
is used. ** Except for helium, which has only two valence electrons.

Periodic table group Valence Electrons

Group 1 (I) (alkali metals) 1
Group 2 (II) (alkaline earth metals) 2
2*
Groups 3-12 (transition metals) (The 4s shell is complete and
cannot hold any more electrons)
Group 13 (III) (boron group) 3
Group 14 (IV) (carbon group) 4
Group 15 (V) (pnictogens) 5
Group 16 (VI) (chalcogens) 6
Group 17 (VII) (halogens) 7
Group 18 (VIII or 0) (noble gases) 8**

Lewis Electron-dot Structures of Representative Element

LEWIS SYMBOLS
We use Lewis symbols to describe valence electron configurations of
atoms and monatomic ions. A Lewis symbol consists of an elemental
symbol surrounded by one dot for each of its valence electrons:

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 Figure
1. shows
the Lewis
symbols
for the
elements
of the
third
period of
the
periodic
table
Lewis
symbols can also be used to illustrate the formation of cations from
atoms, as shown here for sodium and calcium:
Likewise, they can be used to show the formation of anions from
atoms, as shown here for chlorine and sulfur:
Figure 2. demonstrates the use of Lewis symbols to show the transfer of
electrons during the formation of ionic compounds.

Figure 2. Cations are formed when atoms lose electrons,

represented by fewer Lewis dots, whereas anions are formed by atoms
gaining electrons. The total number of electrons does not change.

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LEWIS STRUCTURES
We also use Lewis symbols to indicate the formation of covalent bonds,
which are shown in Lewis structures, drawings that describe the bonding
in molecules and polyatomic ions. For example, when two chlorine atoms
form a chlorine molecule, they share one pair of electrons:

The Lewis structure

indicates that each Cl atom has three pairs of electrons that are not used
in bonding (called lone pairs) and one shared pair of electrons (written
between the atoms). A dash (or line) is sometimes used to indicate a
shared pair of electrons:

A single shared pair of electrons is called a single bond. Each Cl atom

interacts with eight valence electrons: the six in the lone pairs and the two
in the single bond.

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 For each of the following elements, write the symbol and state
whether the element is a METAL, NONMETAL, or METALLOID:
Name Symbol Type of element
Oxygen
Sodium
Silver
Chlorine
Aluminum
Silicon
Lead
Antimony
2. To which family does each of the following elements belong?
Name Symbol Family
Rubidium
Bromine
Strontium
Iron
Krypton
Uranium
3. For each of the following elements, write the LEWIS DOT SYMBOL:
(remember: the A group # is the number of dots)

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 Name Lewis dot symbol Name Lewis dot
symbol

Carbon Hydrogen

Potassium Barium

Nitrogen Aluminum

Argon Selenium

Tin Helium

Answer the following questions.

1. How Are valence electrons and group number reflected in electron
configurations?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
_____________________________________________
2. What makes the study of valence electrons essential?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
_____________________________________________
3. What is the standard pattern in representing the valence electrons in
Lewis structure of the element?

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___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
_____________________________________________
4. Why do we follow certain patterns in chemistry and in life?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
_____________________________________________
Yes No I need some
times
1. I can explain the role of energy in life
processes;
2. I can identify the importance of raw
materials;
3. I can describe the two photosynthetic
reactions in plants;
4. I can explain the role of ATP in life
processes;
5. I can trace the major events of
glycolysis and aerobic respiration;
6. I can define matter;

7. I can determine the structure of an

atom;
8. I can differentiate between elements
and compounds
9. I can define valence electron;

10. I can determine the number of

valence electrons in an atom based on
its position in the periodic table; and
11. I can draw electron-dot structures
of representative elements.

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