8.6B ATOMS IN REACTIONS Use the periodic table to identify the atoms involved in chemical reactions.
3
8.6B – ATOMS IN REACTIONS
DIRECTIONS Below are various food items. Identify and list the components that make up the food item in each image. Which food item might contain the most components, or ingredients? Which food item might contain the least?
Components
Components
Components
Which of these (do you think) is made up of the most elements? Explain. A. NaHCO3 B. HCl C. Ca3(PO4)2
Sodium Bicarbonate Hydrochloric Acid Calcium Phosphate
4
8.6B – ATOMS IN REACTIONS 1
Would you happen to know how to bake a cake? If asked to explain how to bake a cake, what might we need? For starters, a recipe. A cake recipe includes ingredients like flour, sugar, and eggs and instructions like mix and bake.
2
The Periodic Table of Elements contains all known elements arranged by increasing atomic number. It holds the ingredients for a chemical equation. Like a cake recipe, a chemical equation has ingredients and instructions for making something new.
3
A chemical formula is expressed using symbols that represent elements. Each symbol can be found and identified on the periodic table. For example, Fe is the symbol for Iron, and O is the symbol for Oxygen. Each symbol also tells us how many atoms of the element are present, with a subscript.
4
A subscript is used in chemical formulas to indicate the number of atoms of an element present in a molecule or compound. For example, H₂ means that there are two hydrogen atoms. If a symbol has no subscript, there is only one atom of that element. Consider the following: CO₂. In this example, there is only one atom of Carbon, C, since no subscript is present. In comparison, there are two atoms of Oxygen, O. C O
O
5
C.9D T-TESS
1.1, 2.2
7.6B
8.6B – ATOMS IN REACTIONS 5
A coefficient is the number in the front of a molecule and tells us how many molecules there are. When there is a coefficient, we must multiply all elements in the formula by the coefficient. For example, in 6CO₂, there are one Carbon and two Oxygen atoms, but we must multiply both by the coefficient – six. So there are six Carbon atoms (1 x 6 = 6) and twelve Oxygen (2 x 6 = 12) atoms.
ACTUALITY Ammonium nitrite (NH₄NO₂) contains four different elements. True or false? Explain.
K2SO4 ELEMENT
NO. OF ATOMS
TOTAL
VISUAL
Go to Question
ATOM 001
6
8.6B – ATOMS IN REACTIONS ATOM 001
Li2CO3 Lithium carbonate is a white, crystalline salt compound used as an electrolyte in rechargeable batteries. This question has two parts. First, answer Part A. Then, answer Part B. PART A Which elements are represented in the formula? Select THREE correct answers. ☐ Lithium ☐ Iodine ☐ Cobalt ☐ Oxygen ☐ Carbon PART B Which evidence supports the answer to Part A? A. There are 2 atoms of Iodine, 1 atom of Cobalt, and 3 atoms of Oxygen. B. There are 2 atoms of Lithium, 1 atom of Carbon, and 3 atoms of Oxygen. C. There are 2 atoms of Lithium, 1 atom of Cobalt, and 3 atoms of Oxygen. D. There are 2 atoms of Iodine, 1 atom of Carbon, and 3 atoms of Cobalt.
7
8.6B – ATOMS IN REACTIONS
2 RUBRIC The scoring model for this multi-select/multi-part question is: ■ To obtain full credit (2 points), you must correctly answer Parts A and B. ■ To obtain partial credit (1 point), you must correctly answer Part A. ■ You will receive 0 points if the answer is missing or incorrect.
8
8.6B – ATOMS IN REACTIONS
CHEMICAL REACTIONS 6
A chemical equation uses symbols, subscripts, and coefficients to show a chemical reaction. For example, in this formula, we combine two molecules of Hydrogen gas and one molecule of Oxygen gas to create two water molecules.
2H2 O2
2H2O The chemical formula for water.
7
A chemical equation contains two parts: reactants and products. The reactants are the substances that react to create a new substance(s) before the chemical reaction, . located on the left side of the arrow
→
8
The products are the new substance(s) created after the chemical reaction, located on the right side of the arrow in the chemical equation. In the chemical equation for water, Hydrogen and Oxygen gas are the reactants, and water is the product of that reaction.
→
R
A
P
2H2 O2
2H2O
9
8.6B – ATOMS IN REACTIONS T-TESS
9
2.3
Some of the most common mistakes when identifying atoms in chemical reactions include confusion between elements and compounds, mix-up chemical symbols of elements, and failure to use the Periodic Table of Elements. Elements and compounds are often mistaken when the letters involved are identical. For example, CO and Co include the same letters but differ altogether. Co is an element known as Cobalt. In comparison, CO is a compound made of elements, Carbon and Oxygen. It is important to note that this error can be resolved by paying close attention to uppercase and lowercase letters.
CO
Co
ELEMENT(S)
ELEMENT(S)
6
8
27
C
O
Co
12.011
15.999
58.933
Carbon
Oxygen
Cobalt
Chemical symbols for the elements – Carbon, Oxygen and Cobalt.
10
This error commonly causes a mix-up between chemical symbols of elements. For example, Chlorine – Cl is commonly mistaken for a capital "C" and a capital "I." The chemical symbol for Chlorine is an uppercase "C" and a lowercase "L," not two uppercase letters. Finally, the last mistake involves using the wrong symbol for the wrong elements. For example, using P instead of K for Potassium. Not all symbols
10
8.6B – ATOMS IN REACTIONS contain letters from the name. For example, the symbol for Mercury is Hg.
ACTUALITY True or false? In the equation, 8H₂O + 14CO₂ → 2C₇H₈ + O₂, the following are the reactants: 8H₂O and 2C₇H₈. Explain.
DISCUSS
8Ag₂S → 16Ag + S₈ How many elements are represented in the chemical equation, AND how many atoms of each element (Ag and S atoms) are on each side of this chemical equation?
CH4
2O2
CO2
ELEMENT(S)
11
2H2O
8.6B – ATOMS IN REACTIONS
CH4
2O2
CO2
2H2O
WRAP IT UP 11
A chemical formula shows a chemical reaction using symbols. To determine which atoms are involved in a chemical reaction, we must use the periodic table to determine the symbols of the elements. A chemical formula has two parts: reactants and products. Reactants will react to create a new substance and are on the left side of the arrow. Products are the new substances made after a chemical reaction and are on the right side of the arrow.
Go to Question
ATOM 002
12
8.6B – ATOMS IN REACTIONS ATOM 002 DIRECTIONS Fill in the blanks to identify the atoms involved in the chemical equation. Record your answers in the spaces provided. How many atoms of each element are represented in the products of this equation?
2NH3 + 3I2 → N2I6 + 3H2 There are 1 atom(s) of Hydrogen, 2 atom(s) of Nitrogen, and 3 atom(s) of Iodine represented in the products of this chemical equation. 1. _______ 2. _______ 3. _______
13
8.6B – ATOMS IN REACTIONS
1 RUBRIC The scoring model for this text entry question is: ■ To obtain full credit (1 point), you must enter the correct answer in the box. ■ You will receive 0 points if the answer is missing or incorrect.
14
8.6B – ATOMS IN REACTIONS
THINKING AHEAD 12
T-TESS
Not all reactants in a chemical reaction are used entirely, meaning some reactants will be left over. The limiting reactant is the reactant that determines how much product is created, since it is entirely consumed during the reaction. For instance, suppose there is not enough O₂ in the equation 2H₂ + O₂ → 2H₂O, then H₂ is the limiting reactant. To figure out which reactant is limiting, chemists use a mathematical technique called stoichiometry.
13
The limiting reactant sets the amount of product that can be produced, in essence, limiting how much product is formed. Any reactant leftover from the reaction is known as the excess reactant. At the end of a reaction, we typically find some excess reactant, while the limiting reactant will have been entirely consumed.
15
1.1
8.6B – ATOMS IN REACTIONS
GET IN LINE 14
The periodic table allows scientists to identify elements by their symbols and properties. Similarly, in mathematics, linear relationships allow us to identify and analyze relationships between variables. Much like we determine characteristics such as slope or y-intercept by analyzing a graph, chemists use the periodic table to identify the elements in a compound.
T-TESS
2.2
15
In linear equations, such as y = mx + b, the graph provides a clear representation of how one variable relates to another. The term 'b' represents the y-intercept, which shows where the line crosses the y-axis. For the equation y = x + 2, the y-intercept is 2. This means that when 'x' is 0, 'y' equals 2, positioning the line at the point (0,2) on the graph. Y
20
y=x+2
15 10 5 X
X
-5
5
10
-5 Y 16
15
20
8.6B – ATOMS IN REACTIONS 16
By analyzing different equations, we can determine where each line crosses the y-axis. For example, in the equation y=2x+1, the line intersects the y-axis at (0,1). Likewise, in the equation y=−3x−4, the line crosses the y-axis at (0,-4). Lastly, in the equation y=0.5x+7, the line meets the y-axis at (0,7). These points where the lines meet the y-axis are commonly called the y-intercepts of the lines. Y
15 10 5 X
X
-3
-2
-1
1
2
3
-5 -10 -15 y = 2x + 1
Y y = 0.5x + 7
17
y = -3x – 4
8.6B – ATOMS IN REACTIONS
BRING IT AROUND 17
We use the periodic table to identify atoms involved in chemical reactions. By identifying the atoms and elements taking part in these reactions (chemical equations), we can observe that atoms of elements simply shift around or rearrange. No matter how these atoms shift and move, the total number remains the same on both sides. This principle is known as the law of conservation of mass.
18
The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass (and atoms) of reactants before a reaction must be equal to the total mass of products after the reaction. For instance, in the synthesis of carbon dioxide from carbon and oxygen:
REACTANTS
ARROW
PRODUCTS
C
O2
CO2
C
O
O C
O
O
Synthesis of carbon dioxide from carbon and oxygen.
18
8.6B – ATOMS IN REACTIONS 19
In this reaction, one carbon atom and two oxygen atoms exist on each side of the equation. This visual representation demonstrates the law of conservation of mass by maintaining the balance of atoms and mass, indicating that no atoms are lost or gained.
19
8.6B – ATOMS IN REACTIONS
CaS (s) ELEMENT
No. ATOMS
TOTAL
FeS (s) ELEMENT
TOTAL
No. ATOMS
2HCl (aq)
CaCl2 (aq)
ELEMENT
ELEMENT
No. ATOMS
No. ATOMS
TOTAL
TOTAL
2HCl (aq)
FeCl2 (aq)
ELEMENT
ELEMENT
No. ATOMS
TOTAL
TOTAL
20
H2S (g) ELEMENT
No. ATOMS
TOTAL
No. ATOMS
H2S (g) ELEMENT
TOTAL
No. ATOMS
8.6B – ATOMS IN REACTIONS
FeCl2 (aq) ELEMENT
No. ATOMS
TOTAL
TOTAL
ELEMENT
FeS (s)
No. ATOMS
ELEMENT
TOTAL
NaOH (aq) ELEMENT
H2S (g)
No. ATOMS
TOTAL
HCl (aq) ELEMENT
No. ATOMS
ELEMENT
TOTAL
TOTAL
21
ELEMENT
No. ATOMS
TOTAL
NaCl (aq)
No. ATOMS
2HCl (aq)
No. ATOMS
H2O (l) ELEMENT
TOTAL
No. ATOMS
8.6B – ATOMS IN REACTIONS
4NH3 (g) 5O2 (g)
4NO (g) 6H2O (l)
=
+
+
=
=
+
+
=
=
+
+
=
=
+
+
=
2KI (aq)
Cl2 (g)
2KCl (aq)
I2 (s)
=
+
+
=
=
+
+
=
=
+
+
=
=
+
+
=
22
8.6B – ATOMS IN REACTIONS
CH4
2O2
(g)
CO2
(g)
2H2O
(g)
(g)
=
+
+
=
=
+
+
=
=
+
+
=
=
+
+
=
3Ca(OH)2 2H3PO4
Ca3(PO4)2 6H2O
=
+
+
=
=
+
+
=
=
+
+
=
=
+
+
=
(s)
(l)
(s)
23
(l)
8.6B – ATOMS IN REACTIONS
CHEMICAL SYMBOLS C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
O
O
O
O
O
O
O
O
N
N
N
N
N
N
N
N
P
P
P
P
P
P
P
P
S
S
S
S
S
S
S
S
Na
Na
Na
Na
Na
Na
Na
Na
Ca
Ca
Ca
Ca
Ca
Ca
Ca
Ca
K
K
K
K
K
K
K
K
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
24
8.6B – ATOMS IN REACTIONS
CHEMICAL SYMBOLS C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
O
O
O
O
O
H O
O
O
6
7
8
PERIODIC TABLE 1
2
3
4
5
H
He
Li
Be
B
C
N
O
1.008
4.0026
6.94
9.0122
10.81
12.011
14.007
15.999
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
9
10
11
12
13
14
15
16
F
Ne
Na
Mg
Al
Si
P
S
18.998
20.180
22.980
24.305
26.982
28.085
30.974
32.06
Flourine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
17
18
19
20
31
32
33
34
Cl
Ar
K
Ca
Ga
Ge
As
Se
35.45
39.948
39.098
40.078
69.723
72.630
74.922
78.971
Chlorine
Argon
Potassium
Calcium
Gallium
Germanium
Arsenic
Selenium
35
36
37
38
51
52
53
54
Br
Kr
Rb
Sr
Sb
Te
I
Xe
79.904
83.798
85.468
87.62
121.76
72.630
126.90
131.29
Bromine
Krypton
Rubidium
Strontium
Antimony
Tellurium
Iodine
Xenon
1
1
1
6
6
8
8
8
H
H
H
C
C
O
O
O
1.008
1.008
1.008
12.011
12.011
15.999
15.999
15.999
Hydrogen
Hydrogen
Hydrogen
Carbon
Carbon
Oxygen
Oxygen
Oxygen
25
8.6B – ATOMS IN REACTIONS
1.
Which balanced equation represents a reaction with five different elements? 1. Na2CO3 + HCl → NaCl + H2O + CO2 2. C7H6O2 + O2 → CO2 + H2O 3. Fe2(SO4)3 + KOH → K2SO4 + Fe(OH)3 4. Ca3(PO4)2 + SiO2 → P4O10 + CaSiO3 A. Equations 1 and 4 B. Equations 3 and 4 C. Equations 1 and 3 D. Equations 2 only
2.
A student showed the teacher a chemical equation. The teacher said, "This equation is not balanced. There are different numbers of atoms on each side.”
C6H6 + 5O2 → 6CO2 + 2H2O How many atoms of each element are found in the product side of this unbalanced chemical equation? A. 6 carbon atoms, 4 hydrogen atoms, and 14 oxygen atoms. B. 6 carbon atoms, 6 hydrogen atoms, and 14 oxygen atoms. C. 6 carbon atoms, 4 hydrogen atoms, and 13 oxygen atoms. D. 6 carbon atoms, 2 hydrogen atoms, and 12 oxygen atoms.
26
8.6B – ATOMS IN REACTIONS
3.
Below are two balanced chemical equations. REACTION 1
Ca(HCO3)2 → CaCO3 + CO2 + H2O REACTION 2
CaCO3 + CaO → CO2 Which statement correctly compares both chemical equations? A. The second reaction has twice the number of calcium atoms as the first reaction. B. Both reactions involve calcium and carbon atoms, but only the first reaction has hydrogen atoms. C. Both reactions start with compounds having the same number of oxygen atoms, but the first reaction ends with more oxygen atoms due to the extra products. D. The first reaction has two more carbon atoms than the second reaction.
27
8.6B – ATOMS IN REACTIONS
4.
Below are two reactions involving hydrochloric acid. REACTION 1 Reaction between sodium carbonate and hydrochloric acid
Na2CO3 + 2HCl → 2NaCl + H2O + CO2 REACTION 2 Reaction between sodium bicarbonate and hydrochloric acid
NaHCO3 + HCl → NaCl + H2O + CO2 Based on the information, which statement is NOT true about the reactions? Select TWO correct answers.
☐ Both reactions start with the same number of hydrogen and sodium atoms. ☐ Reaction 1 utilizes a greater number of chlorine atoms than Reaction 2. ☐ Both reactions have the same number of elements. ☐ Reaction 2 starts with more carbon atoms than Reaction 1. ☐ Reaction 1 begins with more oxygen atoms than Reaction 2. RUBRIC The scoring model for this multi-select question is: ■ To obtain full credit (2 points), the student will correctly select two statements that are NOT true. ■ To obtain partial credit (1 point), the student will correctly select one statement that is NOT true. ■ Students will receive 0 points if both selections are missing or incorrect.
28
8.6B – ATOMS IN REACTIONS
5.
Which of the following chemical equations contains three elements? Select TWO correct answers.
CaO + H2O → Ca(OH)2 4Al + 3O2 → 2Al2O3 K + NaCl → KCl + Na 2Na + Cl2 → 2NaCl AgNO2 + NaCl → AgCl + NaNO2
RUBRIC The scoring model for this multi-select question is: ■ To obtain full credit (2 points), the student will correctly select two chemical equations that contain three elements. ■ To obtain partial credit (1 point), the student will correctly select one chemical equation that contains three elements. ■ Students will receive 0 points if both selections are missing or incorrect.
29
8.6B – ATOMS IN REACTIONS T-TESS
EXIT TICKET
2H2 + O2 → 2H2O
2.3
Which element(s) are represented in the chemical equation, AND how many total atoms of each element are represented on the reactant side? Product side?
ZnCO3 → ZnO + CO2
SHORT CONSTRUCTED RESPONSE
Zinc carbonate is a solid, white substance that breaks down into a solid, yellow substance and creates carbon dioxide when heated. Which elements are represented in the chemical equation, AND how many atoms of each element in the reactants are represented in the chemical equation? Read the question carefully. Then enter your answer in the space provided.
30
8.6B – ATOMS IN REACTIONS
X
#
# R
A→ 31
P
8.6B – ATOMS IN REACTIONS
32
8.6B
ATOM Átomo
ELEMENT Elemento
COMPOUND Compuesto
MOLECULE Molécule
CHEMICAL FORMULA Fórmula Quimica
8.6B – ATOMS IN REACTIONS
PERIODIC TABLE Tabla periódica
VOC 33
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Basic units of matter, consisting of protons, neutrons, electrons.
A table showing all the elements that have been discovered.
Unidades básicas de la materia.
Una tabla que contiene todos los elementos químicos. ACADÉMICO
Átomos en reacciones químicas
Átomos en reacciones químicas Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Substances formed when two or more elements chemically combine.
Substances consisting of a single type of atom.
Sustancias formadas cuando dos o más elementos se combinan químicamente.
ACADÉMICO
Átomos en reacciones químicas Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Symbols showing the elements present in a compound and their relative proportions.
Formed when two atoms (same or different) are chemically combined.
Formada cuando dos o más átomos (iguales o diferentes) se combinan químicamente.
Símbolos que muestran los elementos presentes en un compuesto.
ACADÉMICO
ACADÉMICO
Átomos en reacciones químicas
Átomos en reacciones químicas
34
Átomos en reacciones químicas
VOC
ACADÉMICO
Sustancias que consisten en un solo tipo de átomo.
8.6B – ATOMS IN REACTIONS
ACADÉMICO
8.6B
Atoms in Chemical Reactions
8.6B
CHEMICAL EQUATION Ecuacion química
REACTANT Reactivo
YIELD Rendimiento
PRODUCT Producto
COEFFICIENT Coeficiente
8.6B – ATOMS IN REACTIONS
CHEMICAL REACTION Reaccion química
VOC 35
Sustancias producidas en una reacción química.
Números que indican la cantidad de una sustancia en una ecuación.
ACADÉMICO
ACADÉMICO
Átomos en reacciones químicas
Átomos en reacciones químicas
Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Numbers in front of formulas in equations showing quantity.
Substances produced in a chemical reaction. Átomos en reacciones químicas ACADÉMICO
36
VOC
Átomos en reacciones químicas ACADÉMICO
Sustancias presentes al comienzo de una reacción química.
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Arrow in a chemical equation indicating result of reaction.
Substances present at the start of a chemical reaction. Átomos en reacciones químicas ACADÉMICO
8.6B – ATOMS IN REACTIONS
Flecha en una ecuación química que indica el resultado.
Atoms in Chemical Reactions Átomos en reacciones químicas ACADÉMICO
Representación simbólica de una reacción química.
Procesos donde las sustancias se convierten en nuevas sustancias.
8.6B
Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Symbolic representation of a chemical reaction.
Processes where substances change into new substances.
8.6B
SUBSCRIPT Subíndice
8.6B – ATOMS IN REACTIONS VOC 37
ACADÉMICO
ACADÉMICO
Átomos en reacciones químicas
Átomos en reacciones químicas
38
VOC
Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Átomos en reacciones químicas ACADÉMICO
Átomos en reacciones químicas ACADÉMICO
8.6B – ATOMS IN REACTIONS
Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC
Átomos en reacciones químicas ACADÉMICO
Átomos en reacciones químicas ACADÉMICO
Números pequeños que indican el número de átomos en una fórmula.
8.6B
Small numbers in formulas indicating number of atoms. Atoms in Chemical Reactions
Atoms in Chemical Reactions
ACADEMIC
ACADEMIC