CP2 review

Checkpoint 2 Review

8th Grade Science

Counting Atoms - Conservation of Mass

How to count atoms in a chemical formaula.

• You already know how to read SUBSCRIPTS

• A subscript tells us how many of each atom there are

Multiple Choice

How many Sodium atoms are there in NaCl?

• 1

• 2

• 3

• 4

Multiple Choice

How many Magnesium atoms are there in Mg₃N₂?

• 1

• 2

• 3

• 4

Multiple Choice

How many Hydrogen atoms are there in Pentane, C₅H₁₂?

• 5

• 12

• 1

• 2

We CANNOT change the subscript, it would become something totally different!

• Add a subscript of 2 after Oxygen and you make Hydrogen Peroxide.

Coefficiant

• The large number in FRONT of the symbol. You have to multiply this number by all of the subscripts.

• 4 Iron Atoms

• 6 Oxygen Atoms

Multiple Choice

How many Hydrogens are in 2H₂O?

• 2

• 4

• 6

• 1

Multiple Choice

How many Oxygens are in 6H₂O?

• 2

• 12

• 6

Multiple Choice

How many Carbons are in 3CO₂?

• 3

• 6

• 2

Balanced Equations

• Follow the Law of Conservation

• Have the same number and type of atoms on both sides

• They just get rearranged!

Multiple Choice

Balanced or Not?

H₂ + Cl₂ ---> 2HCl

• Balanced

• Unbalanced

H₂ + O₂ ---> H₂O

The hydrogen are balanced, but the oxygens are not.

You CAN change the coefficient.

You CANNOT change the subscript.

We put a two in front of the water and this balances the oxygen.

H₂ + O₂ ---> 2H₂O

But....

H₂ + O₂ ---> 2H₂O

Reactants: 2H, 2O Products: 4H, 2O

• This causes the hydrogen to become unbalanced.

• To fix this, we place a two in front of the hydrogen on the left side.

  2H₂ + O₂ ---> 2H₂O

2H₂ + O₂ ---> 2H₂O

• It's balanced now!

• 4 H and 2 O

Multiple Choice

Balanced or Not?

H₂ + O₂ ---> H₂O

• Balanced

• Not

Multiple Choice

Balanced or not?

N₂+6H₂ ----> 2NH₆

• Balanced

• Unbalanced

Multiple Choice

Which of the following equations is balanced?

• P₄ + 3O₂ ---> 2P₂O₃

• N₄ + 3F₂ ---> 2NF₃

• 2LiF + Br₂ ---> 2LiBr + F₄

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

Multiple Choice

In this reaction, how much CO₂ is produced?

• 42 g

• 24 g

• 23 g

• No grams produced

Multiple Choice

Does this equation follow the Law of Conservation of Mass?

2Fe₂O₃ + 3C → 4Fe + 3 CO₂

• No, because there are more reactants than products.

• No, because there are more products than reactants.

• Yes, because the reactants equal the products.

• Yes, because the reactants do not equal the products.

Multiple Choice

O + H₂ → H₂O

32 g of Oxygen completely reacts with 8 g of Hydrogen to produce _____ g of water.

• 8

• 12

• 24

• 40

Multiple Choice

Mg + F → MgF

24 g of magnesium reacts with 38 g of fluorine to produce _____ g magnesium fluoride.

• 62 
• 38
• 24
• 14

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.

Multiple Choice

What is the symbol for Iron?

• Ir

• In

• Fe

• FE

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.

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

How many Aluminum atoms are in Al₂O₃?

• 3

• 2

• 5

• 1

Multiple Choice

How many atoms are there TOTAL in H₂SO₄ ?

• 6

• 5

• 7

• 3

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 elements are in C₆H₁₂O₆?

• 1
• 2
• 3
• 4

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

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

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

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/ Bubbles

• LIGHT PRODUCTION

• TEMPERTURE CHANGE

• ODOR

• NEW substances

• 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

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

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

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 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

Types of Forces

Contact forces: These require physical

contact between objects.

Friction

Applied Forces

Normal Forces

Multiple Choice

Two object must touch each other for a contact force to have happened

• yes

• no

Friction

• Friction is a force that slows motion when two objects

rub against each other

• Friction opposes motion

Multiple Choice

Friction ______ Motion.

• helps motion

• opposes (slows) motion

●rubbing both the hands
together to create heat

●a child sliding down through a
slide in a park

●a book sliding across a table

●a book resting on a table

●a car parked on a hill

●a ladder leaning against a
wall

●A moving car

●rolling a soccer or tennis ball

●a marble rolling on the floor

Open Ended

Give one example of friction

Applied Force

A force that is applied to an object by

another object or person

• when you push a door open

• kick a ball

• pull a drawer out

Multiple Choice

An example of applied force is _______.

• rain falling

• earth orbiting

• kicking a ball

Normal Forces

Upward push of a surface on an object

that keeps the object from falling through.

● Books sitting on a table

● A person sitting on a tabletop

Multiple Choice

Normal forces

• make objects fly

• keep objects from falling through surfaces

• give objects speed

Open Ended

Give and example of a normal force.

Non-contact forces: These act on objects
even if they are not physically touching.

Gravity

Magnetism

Gravitational Force

The attraction between two objects

with mass, such as Earth pulling objects

toward its center.

● Rain falling to Earth
● Tides in the ocean

● Earth’s revolution around the sun

Drag and Drop

Gravitation force happens between two objects with _______.

Placeholder

Drag these tiles and drop them in the correct blank above

mass

color

shape

size

Net Force review

As a review- Net force is the combination of forces on an object.​

Answer will need the netforce (in Newtons) and the direction

Net Force

Multiple Choice

What is Force?

• A pull exerted on an object

• A push exerted on an object

• A push or pull exerted on an object

• Nothing

Multiple Choice

What is the unit for FORCE? 

• N (Newtons)

• lbs (pounds)

• g (grams)

• m/s (meters per second)

As a Review:

• If the forces are going in the same direction: you add the forces

• If the directions are going in different directions: you subtract the forces

• If there is a combination: add the ones that are the same, then subtract the different directions.

Multiple Choice

How do you find the net force of this image.

• Add up all the arrows

• Add a green arrow and the orange arrow.

• Subtract all the arrows.

• Add the green arrows and subtract the orange arrow.

Multiple Choice

Is the Net Force balanced or Unbalanced?

• Balanced

• Unbalanced

Multiple Choice

What is the Overall Net Force and which side has a greater Net Force?

• 12, Right

• 0, Both are balanced

• 12, Both are balanced

• 0, Left

Multiple Choice

What is the net force and to what direction.

• 210 N to the right

• 280 N to the right

• 110 N to the left

• 180 N to the left

Multiple Choice

Which one is balanced?

• top

• bottom

• both

• Neither is balanced

Multiple Choice

What is the net force?

• 17 N Right

• 3 N Right

• 3 N Left

• 17 N Left

Multiple Choice

Which direction will the object move?

• Up

• Down

• Right

• Left

Multiple Choice

What is the net force?

• 65 N left

• 65 N right

• 35 N left

• 35 N right

Multiple Choice

If the wind is heading south with a force of 5 N, and a car is going north with force of 78936 N, what is the Net Force and Direction.

• 78931 N North

• 78931 N South

• 78531 N North

• 78531 N South

Multiple Choice

If a car has a force of 54 N forwards and the brakes have a force of 73 N backwards, what is the overall Net Force.

• 16 backwards

• 19 forwards

• 18 backwords

• 23 forwards

Multiple Choice

If a boat traveling East has a Net Force of 324 N, and the wind blowing West has a Net Force of 789 N. What is the overall Net Force and which side?

• 465 N, East

• 465 N, West

• 1113 N, West

• 1113 N, East

Newton's Laws of Motion

Multiple Choice

What is Newton's First Law

• F=ma
• Every action has an equal and opposite reaction
• An object at rest stays at rest, an object in motion stays in motion. 
• Friction 

Multiple Choice

Which type of force(s) will cause a change in an object's motion?

• gravity
• zero net force
• balanced forces
• unbalanced forces

Multiple Choice

According to Newton’s first law of motion, a moving object that is not acted on by an unbalanced force will

• remain in motion.
• eventually come to a stop.
• change its momentum.
• accelerate.

Multiple Choice

What is Newton's First Law known as? The Law of

• Friction
• Mass
• Inertia
• Gravity

Multiple Choice

What is inertia?

• the force that opposes motion
• the force of attraction between 2 objects
• an object's tendency to stay in motion or to stay at rest
• a change in an object's speed and/or direction

Multiple Choice

Why does an 18-wheeler have more inertia than a bicycle?

• it has more mass
• it has more volume
• it is not as aerodynamic

Multiple Choice

What is Newton's 2nd Law?

• Every action has an equal and opposite reaction

• An object at rest stays at rest, an object in motion stays in motion.

• F = ma

• Friction

Multiple Choice

A greater applied force is required to move an object with a greater mass than one with a smaller mass.

• True
• False

Multiple Choice

The SI units for force are...

• Kilograms
• Newtons
• Meters per second
• Pounds

Multiple Choice

Unit of mass

• m/s 2
• m/s
• newtons
• kg

Multiple Choice

You push on a tree with 20 N of force. If the tree doesn't move, the tree is pushing back on you with _____of force.

• 20N

• 10N

• 40N

• 70N

Multiple Choice

The mass of a wagon is 40 kg. The wagon accelerates at 8 m/s² . What is the force?

• 38.25 Kg

• 320N

• 5N

• 3.825Kg

Also known as the "Law of Action/Reaction"

Multiple Choice

Newton's Third Law States...

• Objects in motion stay in motion and objects at rest stay at rest
• Force is equal to mass times acceleration
• For each action there is an equal and opposite reaction

Multiple Choice

A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction force is...

• The grip of the player's hands on the ball
• the air resistance of the ball
• the force of the ball against the bat

Multiple Choice

Two students with different masses are sitting in roll-y chairs. The lighter one uses his feet to push the other

• The lighter student will move faster because he has less mass

• The heavier student will move more because he is being pushed

• They will move with the same speed

• The heavier student shouldn't move at all

Multiple Choice

When you hit a tennis ball with a racket...

• The ball exerts more force on the racket

• The ball and racket exert the same force on each other

• The racket exerts more force on the ball

• It depends on how hard you hit it