G10_5.1: Reactions and Equations

Reactions and Equations

Pg 150 - 156

Lesson 1

Focus Question

How are chemical reactions modeled?

New Vocabulary

chemical reaction

reactant

product

chemical equation

coefficient

Review Vocabulary

chemical change: a process involving one or more
substances changing into a new substance

QUIZLET PRACTICE

https://quizlet.com/class/23470035/

Multiple Choice

The substances present before a chemical reaction occurs; in a chemical reaction the arrow usually points away from the reactant(s)

• chemical reaction

• products

• arrow

• reactants

Multiple Choice

The substances that are formed during a chemical reaction; in a chemical reaction the arrows point toward the product

• arrow

• chemical reaction

• reactants

• products

Multiple Choice

The number before the chemical formula; it represents the number of molecules that are present Ex. 2H₂O₂, 2 molecules of H₂O₂

• reactant

• coefficient

• product

• subscript

Multiple Choice

A chemical change; a process that changes substances into new substances

• physical change

• chemical reaction

• reactant

• product

Multiple Choice

(chemistry) a process in which one or more substances are changed into others

• physical change

• matter

• chemical reaction

• solution

Multiple Choice

What does chemical formula mean?

• letters and numbers showing the types and number of atoms that repeat to make up a substance

• a process in which atoms rearrange to form new substances

Chemical Reactions

• The process by which the atoms of one or

more substances are rearranged to form
different substances is called a chemical
reaction.

• A chemical reaction is another name for a

chemical change.

Chemical Reactions

Evidence of a Chemical Reaction
• A temperature change can indicate a chemical

reaction. Many reactions release energy in the
form of heat and light. Other chemical
reactions absorb heat.

• Color change can indicate a chemical reaction.
• Odor, gas bubbles, and the formation of a solid precipitate are other indications of chemical change.

Multiple Select

You know that a chemical reaction is occurring here because you see __________________ . (Pick 3)

• purple color

• smoke

• ice formation

• fire

• a yellow precipitate

Multiple Choice

The result of the experiment between Iodine and Aluminum was the production of __________________.

• clear liquid.

• a white powder.

• yellow precipitate.

• bubbles.

Multiple Choice

When zinc reacted with hydrochloric acid, what was the result of this reaction?

• a white powder

• a blue liquid

• a brown precipitate

• a gas

Multiple Choice

In this chemical reaction, what was the first evidence that you saw?

• Production of fire

• Production of light

• Production of purple smoke

• Production of white powder

Multiple Choice

A precipitate is a ___________ that forms when 2 liquids react together.

• solid

• liquid

• gas

• plasma

Multiple Choice

We know that there was a chemical reaction occurring when 2 clear liquids were mixed together. That is because we show the production of a _____________.

• solid.

• precipitate.

• gas.

Multiple Select

Which of the following are evidence of a chemical reaction? (Pick more than one.)

• Tearing paper.

• Change in color.

• Production of a gas.

• Change in temperature.

• Production of a precipitate.

Multiple Choice

Reactants are the chemicals that are present at the beginning of an experiment. Reactants react together to make the product.

We can know that a chemical reaction is occurring when we see ______.

• that the product looks just like the reactants.

• nothing new.

• that the product looks different from the reactants.

Representing Chemical Reactions

• Equations are used to

represent chemical
reactions.

• Equations show a

reaction’s reactants
(starting substances) and
products (substances
formed).

• The table shows the

symbols used in chemical
equations.

Multiple Choice

Which symbol is used to indicate a gas?

Multiple Choice

Which symbol is used to indicate a liquid?

Multiple Choice

Which symbol is used to indicate a solid?

Multiple Choice

Which symbol is used to indicate a substance dissolved in water to form a solution?

Multiple Choice

In a chemical equation, the arrow symbol pointing right could mean all of the following EXCEPT...

• yields

• produces

• forms

• precipitates

Multiple Choice

Which symbol is used to indicate that a reaction is reversible?

Multiple Choice

What does the following image represent, in a chemial equation?

• do not store in cold temperatures

• the temperature at which the reaction was carried out

• products must be kept in the refrigerator

• products will be cold

Representing Chemical Reactions

Word Equations
aluminum(s) + bromine(l) → aluminum bromide(s)
• In this word equation, aluminum(s) + bromine(l)

→ aluminum bromide(s) reads as “aluminum and
bromine react to produce aluminum bromide.”

• Word equations lack information about the

number of atoms involved.

Representing Chemical Reactions

Skeleton Equations

Al(s) + Br(l) → AlBr3(s)

• Skeleton equations use symbols and formulas to

represent reactants and products.

• These equations also lack information about the

number of atoms involved.

Representing Chemical Reactions

Chemical Equations
A chemical equation uses chemical formulas to
show the identities and relative amounts of the
substances involved in a chemical reaction.

Balancing Chemical Equations

A coefficient in a chemical equation is the number
written in front of a reactant or product.

Multiple Choice

A math equation is separated by equal (=) sign while a chemical equation is separated by _________.

• an arrow

• a positive sign

• a negative sign

Multiple Choice

The number written before a compound shows the number of __________.

• atoms

• molecules

• reaction

Fill in the Blanks

Multiple Choice

The products are found at the _______ side of the chemical equation.

• right

• left

• center

Multiple Choice

The SMALL number written after an element symbol represents the number of __________.

• atoms

• molecules

• reaction

Multiple Choice

What are the reactants on the image?

• iron nail

• oxygen

• both are correct

Multiple Choice

What is the product on the given image?

• iron nail

• oxygen

• rust

Balancing Chemical Equations

Steps for Balancing Equations
1.

Write the skeleton equation for the reaction.

2.

Count the atoms of the elements in the reactants.

3.

Count the atoms of the elements in the products.

4.

Change the coefficients to make the number of
each element equal on both sides of the equation.
This shows that atoms are conserved.

5.

Write the coefficients in their lowest possible
ratio.

6.

Check your work.

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Writing a Balanced Chemical Equation

Use with Example Problem 1.
Problem
Write the balanced chemical equation for
the reaction in which aqueous sodium
hydroxide and aqueous calcium bromide
react to produce solid calcium hydroxide and
aqueous sodium bromide.

Response
ANALYZE THE PROBLEM
You are given the reactants and products in a
chemical reaction. Start with a skeleton equation,
and use the steps for balancing chemical
equations.

SOLVE FOR THE UNKNOWN

Write the skeleton equation for the chemical
reaction. Be sure to put the reactants on the
left side of the arrow and the products on the
right. Separate the substances with plus signs,
and indicate their physical states.

NaOH(aq) + CaBr2(aq) → Ca(OH)2(s) + NaBr(aq)

•Count the atoms of each element in the
reactants.

1 Na, 1 O, 1 H, 1 Ca, 2 Br

•Count the atoms of each element in the
products.

1 Na, 2 O, 2 H, 1 Ca, 1 Br

EVALUATE THE ANSWER
The chemical formulas for all substances are
written correctly. The number of atoms of
each element is equal on both sides of the
equation. The coefficients are written in the
lowest possible ratio. The balanced chemical
equation for the reaction is

2NaOH(aq) + CaBr2(aq) → Ca(OH)2(s) +
2NaBr(aq)

SOLVE FOR THE UNKNOWN

•Insert the coefficient 2 in front of NaOH to
balance the hydroxide ions.

2NaOH + CaBr2→ Ca(OH)2 + NaBr

•Insert the coefficient 2 in front of NaBr to
balance the Na and Br atoms.

2NaOH + CaBr2→ Ca(OH)2 + 2NaBr

•Write the coefficients in their
lowest-possible ratio.

The ratio of the coefficients is 2:1:1:2.

•Check to make sure that the number of
atoms of each element is equal on both
sides of the equation.

Reactants: 2 Na, 2 OH, 1 Ca, 2 Br

Products: 2 Na, 2 OH, 1 Ca, 2 Br.

Writing a Balanced Chemical Equation

Multiple Choice

What is a coefficient?

• The small number on the right of the chemical symbol.

• The large number to the left of a formula.

Multiple Choice

Which problem is balanced?

• PbO₂ + 2H₂

• SO₂ + H₂0 --> H₂SO₄

• 2Na + 2H₂O --> 2NaOH + H₂

Multiple Choice

Is the equation balanced?: 2H₂O + O₂ --> 4MgO + 3Fe

• Yes

• No

Multiple Choice

Balance this equation
_Zn+_HCl-->_ZnCl₂ +_H₂

• 1,1,2,1

• 1,1,1,2

• 1,2,1,1

• 2,1,1,1

Think of the Quiz answers before moving

to the next slide

Quiz

rotting food

D

boiling water

C

burning wood

B

rusting iron

A

Which of the following is not an example of a
chemical reaction?

1.

Quiz

rotting food

D

boiling water

C

burning wood

B

rusting iron

A

Which of the following is not an example of a
chemical reaction?

1.

CORRECT

Quiz

They are not usually
written if the value is 1.

D

They describe the
highest whole number
ratio of the amounts of
all reactants and
products.

C

They are usually whole
numbers.

B

They are numbers
written in front of
reactants or products.

A

Which of the following is not true about coefficients
in a balanced chemical equation?

2.

Quiz

They are not usually
written if the value is 1.

D

They describe the
highest whole number
ratio of the amounts of
all reactants and
products.

C

They are usually whole
numbers.

B

They are numbers
written in front of
reactants or products.

A

Which of the following is not true about coefficients
in a balanced chemical equation?

2.

CORRECT

Quiz

A solid changes color.

D

A solid melts.

C

A solid is no longer magnetic.

B

There is an odor change.

A

Which observation is NOT physical evidence that a
chemical reaction has occurred?

3.

Quiz

A solid changes color.

D

A solid melts.

C

A solid is no longer magnetic.

B

There is an odor change.

A

Which observation is NOT physical evidence that a
chemical reaction has occurred?

3.

CORRECT

Quiz

Subscripts are changed
to make the number of
each element equal on
both sides.

D

Coefficients are changed
to make the number of
each element equal on
both sides.

C

Coefficients are written
in their lowest possible
ratio.

B

Subscripts should never
be changed to balance
the equation.

A

Which of the following is NOTtrue about balancing
chemical equations?

4.

Quiz

Subscripts are changed
to make the number of
each element equal on
both sides.

D

Coefficients are changed
to make the number of
each element equal on
both sides.

C

Coefficients are written
in their lowest possible
ratio.

B

Subscripts should never
be changed to balance
the equation.

A

Which of the following is NOTtrue about balancing
chemical equations?

4.

CORRECT

Multiple Choice

What is the left part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical equation

Multiple Choice

What is the right part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical Equation

Multiple Choice

How many Mn atoms are found in the following compound?

2MnO₄

• 1

• 2

• 4

• 8

Multiple Choice

What is the little number after an element in a chemical equation called?

Example: H₂

• Coefficient

• Atom

• Subscript

• Equation

Multiple Choice

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO

Multiple Choice

What is the number before a chemical formula called?

Example: 2H₂ + O₂ ---> 2H₂O

• Coefficient

• Atom

• Subscript

• Equation

Multiple Choice

Which of the following equations are correctly balanced?

• 12CO₂ + H₂O ---> C₆H₁₂O₆ + O₂

• CO₂ + H₂O ---> 3C₆H₁₂O₆ + O₂

• CO₂ + 9H₂O ---> C₆H₁₂O₆ + O₂

• 6CO₂ + 6H₂O ---> C₆H₁₂O₆ + 6O₂

Multiple Choice

Balance this equation:

H₂ + Cl₂ ---> HCl

• It is balanced.

• H₂ + Cl₂ ---> 2HCl

• 3H₂ + Cl₂ ---> 6HCl

• H₂ + 3Cl₂ ---> 6HCl