Physical and Chemical Changes

Which of the following is an example of a chemical reaction?

• A marshmallow turning black when heated over a fire
• A powder dissolving in water to make lemonade
• An ice cube melting into a puddle of water
• Salt crystals being crushed into a powder
  

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

What happens when chemical bonds break and new bonds form?

• a physical change
• a chemical reaction
• matter is destroyed
• surface area increases
  

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The principle of conservation of mass is true

• only for reactions that take place in open systems.
• only for reactions that take place in closed systems.
• for reactions in both open and closed systems.
• for no reactions at all.
  

Tags

NGSS.MS-PS1-5

When heated, oxygen reacts with copper to form copper oxide:
If this reaction occurs in a sealed container, will the mass of the container and everything in it increase, decrease, or stay the same and why?

• The mass will stay the same because the number of each kind of atom stays the same.
• The mass will increase because a new kind of molecule is formed.
• The mass will decrease because two substances combine to form one substance.
• More information is needed to tell if the mass will change.
  

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

What is the Law of Conservation of mass?

• Mass is created in a chemical reaction
• Mass is created in a physical change
• New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
• Mass is never created or destroyed

Tags

NGSS.MS-PS1-5

In a reaction A + B ----> C,  reactant A has 5g and product  C has 9g. How many grams should reactant B have? 

• 4g
• 5g
• 9g
• 14g

Tags

NGSS.MS-PS1-5

A chemical reaction is balanced when

• both sides have the same elements
• Both sides have the same  number of atoms
• Same subscripts
• Same coefficients

Tags

NGSS.MS-PS1-5

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

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

Tags

NGSS.MS-PS1-5

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes
• Oxygen is present
• A new substance is produced
• Coal is made up of more than one element

Tags

NGSS.MS-PS1-2

You know you a chemical reaction has occurred if 

• there is a precipitate.
• there is a color change.
• there is a temperature change.
• All of these answers are evidence.

Tags

NGSS.MS-PS1-2