Chapter 3 Review

Chapter 3 Review

1. Physical and Chemical Changes
2. Chemical Reactions
3. Balancing Chemical Equations
4. Types of Chemical Reactions
5. Endo- and Exothermic Reactions
6. Rates of Chemical Reactions

Expectations of the lesson

During this lesson you will review the KEY CONCEPTS of Chemical Reactions.

Each KEY CONCEPT will be briefly explained followed by questions to answer.

Physical and Chemical Change

• A physical change occurs when matter changes its physical properties but not its chemical composition.

• A chemical change occurs whenever matter changes into new substances with different chemical properties.

Multiple Choice

Can you identify the type of Change?

• Physical Change

• Chemical Change

Multiple Choice

Which picture shows a PHYSICAL change?

Signs of a Chemical Reaction occurring

Multiple Select

Which of the following are signs of CHEMICAL CHANGE?

• change in odor

• change in shape

• change in color

• formation of bubbles/gas

Chemical Reactions

• A chemical reaction is a process by which chemical bonds between atoms are broken and new ones are formed. In chemical reactions, substances change into different substances.

• A chemical equation is a statement , used to show changes during a specific chemical reaction.

• A chemical equation involves:

  • the chemical formula of each substance in the reaction  
  • an arrow that indicates the process of change, it can be read as "yields" or "reacts to form"

Look at the description of REACTANTS and PRODUCTS

Multiple Choice

Identify the reactant in the following chemical equation.

 $2Mg\ +\ O_2\ \ \rightarrow\ \ 2MgO$  

•  $2Mg\ \ +\ O_2$  

•  $2MgO$  

Multiple Choice

Identify the PRODUCTS in the following chemical equation.

 $Mg\ +\ CUSO_4\ \ \rightarrow\ \ MgSO_4\ +\ Cu$  

•  $Mg\ +\ CuSO_4$  

•  $MgSO_4\ +\ Cu$  

New Substances

ATOM ARRANGEMENT: The atoms of iron and sulfur are rearranged and new bonds can form to produce iron sulfide.

BOND BREAKING: Each water molecule is made up of two hydrogen atoms joined to one oxygen atom which can decompose by breaking the bonds.

BOND FORMATION: In a compound, the atoms are joined together by strong forces called chemical bonds.

Multiple Select

Identify all the ways new substances can be formed.

• Atom Rearrangement

• Bond Breaking

• Bond Formation

Multiple Choice

Which statement is true for a chemical reaction?

• no new substances are formed

• separate stones from sea water

• new substances are formed

• it is usually easy to reverse the change

Multiple Choice

In the reaction below,

 $CO_2$  is the ...
 $C\ +\ O_2\ \rightarrow\ CO_2$  

• electron

• bond

• reactant

• product

Balancing Chemical Equations

The law of conservation of mass states that mass is never lost or gained in chemical reactions. The total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning. This is because no atoms are created or destroyed during chemical reactions.

How to Balance an equation

• In a balanced chemical equation, the total number of atoms remains the same before and after the reaction.

• How does a chemical equation for any reaction model that mass is conserved during a chemical reaction?

• STEP 1: Determine the number of atoms of each element in the reactants and in the products.

• STEP 2: Count the number of atoms on each side of the equation.

  • If the numbers are equal, then the equation is balanced and if they are not equal, the equation is not balanced.

• STEP 3: Add coefficients to the chemical formulas to balance the equation. 

• STEP 4: Write the balanced chemical equation.

Multiple Choice

 $......\ H_2+.......\ O_2\ \rightarrow\ ......\ H_2O$  

Balance the following equation.

•  $2H_{2\ }+\ 2O_{2\ }\rightarrow\ 2H_2O$  

•  $2H_{2\ }+\ O_2\ \rightarrow\ 2H_2O$  

•  $H_2+\ 2O_2\ \rightarrow\ 2H_2O$  

Multiple Choice

 $......\ NH_3\ \rightarrow\ ......\ H_2+.....\ N_2$  

Balance the following equation.

•  $2NH_{3\ }\rightarrow\ 3H_{2\ }+N_2$  

•  $2NH_{3\ }\rightarrow\ H_{2\ }+2N_2$  

•  $3NH_{3\ }\rightarrow\ 3H_{2\ }+2N_2$  

Multiple Choice

 $......\ CuCO_3\ \rightarrow\ ......\ CO_2+.....\ CuO$  

Balance the following equation.

•  $CuCO_3\ \rightarrow\ 2CO_2+2CuO$  

•  $2CuCO_3\ \rightarrow\ 2CO_2+CuO$  

•  $CuCO_3\ \rightarrow\ CO_2+CuO$  

Types of Chemical Reactions

• Synthesis Reaction: A synthesis reaction occurs when two elements or compounds combine to form one new compound.

• Decomposition Reaction: A decomposition reaction occurs when one reactant breaks down into two or more products.

Types of Chemical Reactions

• Single-replacement Reaction: In a single replacement reaction, one element replaces another element in a compound.

• Double-replacement Reaction: In a double replacement reaction, the two negative ions of two compounds switch places.

Types of Chemical Reactions

• Combustion Reaction: In a combustion reaction, a substance reacts with oxygen and releases energy in the form of heat and light.

Multiple Choice

Which is the correct general equation for a decomposition reaction?

Multiple Choice

Identify the type of reaction for the following equation.

 $2Na\ +\ Cl_2\ \rightarrow\ 2NaC$  

• Combustion

• Double Replacement

• Synthesis

• Single Replacement

Multiple Choice

Identify the type of reaction for the following equation.

 $CuSo_4+Mg\ \ \rightarrow\ MgSO_4+Cu$  

• Combustion

• Double Replacement

• Synthesis

• Single Replacement

Exothermic and Endothermic Reactions

• An exothermic reaction is a chemical reaction that releases thermal energy.

• An endothermic reaction is a chemical reaction that absorbs thermal energy.

Fill in the Blanks

Fill in the Blanks

Poll

I feel confident in my knowledge of Chemical reactions and Equations

• I feel very confident

• I feel I need more practice

• I do not feel confident