8.5(D) & 8.5(E) - Checkpoint 3 Review

8.5(D) & 8.5(E) - Checkpoint 3 Review

8th Grade Science

8.5(D)

Recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing subscripts.

How are elements represented?

• Elements are represented by a chemical symbol.
• This can be a single capital letter OR a capital letter with a lowercase letter.
• ONLY ELEMENTS are on the Periodic Table of Elements - NO COMPOUNDS.

Multiple Choice

What is the symbol for Iron?

• Ir

• In

• Fe

• FE

Multiple Choice

What is the name of the element with the symbol N?

• Sodium

• Nitrogonous

• Nonium

• Nitrogen

Multiple Choice

What is the chemical symbol for Hydrogen?

• Hy

• H

• Hr

• Hn

What are Compounds?

• They are represented by a chemical formula.

• The chemical formula has TWO or MORE elements.

• Every capital letter is a new element present.

Multiple Choice

How many carbon atom/s are present in the compounds CaCO₃?

• 1
• 2
• 3
• 4

Multiple Choice

Can compounds be found in the periodic table?

• Yes

• No

Multiple Choice

Which of the following is not a compound?

• HCl

• Ag

• NaCl

• CO2

Multiple Choice

How many elements are represented in the compound?
Na₂CO₃

• 1
• 2
• 3
• 4

Subscripts

• The small number written directly behind the symbol of an element within a chemical formula.

• It represents the number of atoms of that element. 

  
  

• If you DO NOT see a subscript it means there is ONLY ONE atom.

Subscripts

• If there are parenthesis you must multiply the subscript by all the subscripts (INSIDE) the parenthesis.

• Remember if you DO NOT see a subscript just multiply by one.

Multiple Choice

How many oxygen atoms are in 
Fe(NO₃)₂

• 1
• 2
• 3
• 6

Multiple Choice

How many nitrogen atoms are in 
Fe(NO₃)₂

• 1
• 2
• 3
• 6

Multiple Choice

How many iron atoms are in 
Fe(NO₃)₂

• 1
• 2
• 3
• 6

Multiple Choice

Number written below & to the right of a chemical symbol

• subscript
• reactant
• product
• coefficient

Coefficients

• Number on the left side (or in front) of an element or formula.

• The coefficient tells you how many molecules or compounds you have.

• You must distribute the coefficient by multiplying it with each subscript.

Coefficients

• You must distribute the coefficient by multiplying it with each subscript.

• REMEBER,if there are parenthesis you must multiply the subscript by all the subscripts (INSIDE) the parenthesis.

• THEN multiply all your atoms by the coefficient.

Multiple Choice

Which chemical formula below matches the image shown here?

• $2H_2O$

• $H_4O_2$

• $4H2O$

• $2HO$

Multiple Choice

 $2C_6H_{12}O_6$  

In this chemical formula, which number represents the coefficient (the number of molecules)?

• 2

• 6

• 12

• 1

Multiple Choice

Which image below could represent this formula?

  $2NaCl$  

Multiple Choice

 $3H_2O$  

Which image below matches this chemical formula?

Let's Count Atoms!

Multiple Choice

Are there any compounds on the periodic table?

• yes there are many

• no because only elements are on the periodic table

• I think they are?

• there is no way to tell

Multiple Choice

How many atoms are present if there is no subscript following the element symbol?

• 0

• 2

• only 1

• 1 million

Multiple Choice

How many elements are present in this compound? (Careful!)

Mg₂As₃COHNi₂

• 2

• 4

• 6

• 10

Multiple Choice

How many Aluminum atoms are in Al₂O₃?

• 3

• 2

• 5

• 1

Multiple Choice

A subscript is the small number below the element symbol that tells the number of _______ of that element.

• atoms

• valence electrons

• protons

• elements

Multiple Choice

How many Hydrogen atoms in 3(NH₄)₂CrO₄?

• 4

• 2

• 8

• 24

Multiple Choice

How many Oxygen atoms are in Al₂(SO₄)₃?

• 4

• 12

• 7

• 24

Multiple Choice

How many atoms of Hydrogen are in this compound?

• 1

• 2

• 3

• 4

Multiple Choice

What is C₂H₈O ?

• Element

• Letters

• Numbers

• Compound

Multiple Choice

How many Nitrogen atoms are in (NH₄)₂CrO₄?

• 1

• 2

• 8

• 16

Multiple Choice

How many Sodium atoms are in 6NaCl?

• 1

• 12

• 6

Multiple Choice

How many atoms are there TOTAL in H₂SO₄ ?

• 6

• 5

• 7

• 3

Multiple Choice

How many elements are in C₆H₁₂O₆?

• 1
• 2
• 3
• 4

Multiple Choice

How many Magnesium atoms are in 10MgCl₂?

• 10

• 5

• 20

Multiple Choice

How many Oxygen atoms are in H₂O?

• 1

• 2

• 0

• 4

Multiple Choice

How many Hydrogen atoms are in 4H₂O?

• 6

• 8

• 2

• 4

8.5(E)

Investigate how evidence of chemical reactions indicates that new substances with different properties are formed and how that relates to the law of conservation of mass.

Physical Change

• ONLY changes the form or the appearance of a substance.

• Does not change or form a new substance.

• Phase Changes

Multiple Choice

Which is a physical change?

• burning match 
• vinegar in baking soda 
• melting butter
• cooking an egg

Multiple Choice

How do we know if it is a chemical change?

• can be undone
• cannot be undone
• both
• none

Multiple Choice

Water freezing

• Chemical Change
• Physical Change

Multiple Choice

Ice melting

• Chemical Change
• Physical Change

Multiple Choice

What kind of change occurs if matter changes in amount, size, or shape?

• substance change

• chemical change

• physical change

• elemental change

Chemical Changes

• Substance is transformed into one or more different substances, such as when iron becomes rust.

• IRREVERSIBLE - Cannot change it back to its original form.

• A new product is produced.

Multiple Choice

An explosion occurs ...

• Chemical Change
• Physical Change

Multiple Choice

Change in size ...

• Chemical Change
• Physical Change

Multiple Choice

A change in phase ...

• Chemical Change
• Physical Change

Multiple Choice

Which of the following is NOT an example of a physical change?

• crumpled paper
• pencil sharpening
• shrunken clothing
• sour milk

Multiple Choice

Which of the following is NOT an example of chemical change?

• sour milk
• burning wood
• breaking a pencil
• rust

Multiple Choice

A change in which NEW substances are formed.

• Chemical change
• Physical change
• Casual change
• Formal change

Multiple Choice

A copper penny turning greenish after a few years is an example of ...

• Chemical Change
• Physical Change

Chemical Reactions

•  a process in which atoms of one or more substances (reactants) are rearranged to form one or more new substances (products).

• Chemical changes are the result of chemical reactions.

Indicators of a Chemical Reaction:

• COLOR CHANGE

• GAS PRODUCTION

• LIGHT PRODUCTION

• TEMPERTURE CHANGE

• SMELL/ODOR

• PRECIPITATE

Open Ended

In your own words, tell me what is a precipitate and how is it formed?

Multiple Choice

Identify what type of change happening in the picture below...

• Chemical Reaction

• Physical Change

• Change in State

• Change in appearance only

Multiple Choice

The formation of a solid when two liquids combine is called?

• Solidification

• Freezing

• Precipitate

• Solubility

Multiple Choice

A Chemical Change is also known as what?

• Physical Change

• Physical Property

• Chemical Reaction

• Chemical Property

Multiple Choice

A green powder is heated & a gas is given off while it turns to a black solid. This describes

• Physical Change

• Chemical Change

• Change in State

• Change in Temperature

Multiple Choice

During Chemical Reactions, the new substances created are called?

• Precipitate

• Corrosion

• Reactants

• Products

Multiple Choice

During Chemical Reactions, the substances that are used are called?

• Precipitate

• Corrosion

• Reactants

• Products

The Law of Conservation of Mass

• Mass or matter cannot be created nor destroyed.

• Reactants EQUAL Products

Reactants

• What you START with.

• LEFT side.

• EQUAL to the products.

Products

• What you END with.

• RIGHT side.

• EQUAL to the reactants.

Multiple Choice

Which of the following describes the law of conservation of mass?

• In a reaction, atoms are created or destroyed.
• In a reaction, atoms are not lost or made.
• In a reaction, the mass of the product may be more or less than the reactants.
• In a reaction, mass never stays the same.

Multiple Choice

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

Mass is NEITHER created nor destroyed.

Multiple Choice

A precipitate is a 

• liquid that forms when two solids are reacted
• a solid that forms when two liquids are mixed
• a gas that forms when vinegar and baking soda react
• a change of color in a solution

Multiple Choice

The coefficient in  3H₂O is

• 6
• 2
• 3
• 5

Multiple Choice

A chemical reaction is balanced when

• both sides have the same elements

• Both sides have the same number of atoms

• Same subscripts

• Same coefficients

Multiple Choice

The number in front of a compound or element is a 

• Subscript
• Coefficient
• Superscript
• Charge

Multiple Choice

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

Multiple Choice

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

Multiple Choice

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

Multiple Choice

The blue numbers in the image below represent ________

• I don't know, and don't want to try
• coefficients
• subscripts
• none of the answers are correct

Multiple Choice

Which of the following is NOT a sign of a chemical reaction? 

• Color changes
• Cutting into fourths
• Light is produced
• Gas is formed

Multiple Choice

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

• Coefficient
• reactant
• subscript
• product 

Multiple Choice

A chemical reaction that absorbs heat

• Single replacement
• Exothermic
• Endothermic
• Decomposition

Multiple Choice

The right side of the equation below is called the

• products
• reactants

Multiple Choice

The left side of the equation below is called

• Products
• Reactants

Multiple Choice

How many Carbons are present on the reactant side?

• 1

• 2

• 3

• 4

Multiple Choice

A chemical change is different than a physical change because in a chemical change

• chemicals are used

• molecules do not physically touch

• a new substance is formed and in a physical no new substance is formed

• the change can be seen but in a physical change it cannot

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