Unit 5 - Chemical Reactions Review

What are the evidences/signs that a chemical reaction has occurred? (Select all correct answers)

• Change from solid, liquid, or gas

• Formation of a gas (bubbles, smoke, fizzing, expanding container, new odor)

• A precipitate (solid) forming in a liquid

• Unexpected temperature or color change

• Light is released

What is the BEST definition of a chemical reaction?

• A change in matter that produces one or more NEW substances

• When two things combine and EXPLODE.

Tags

NGSS.HS-PS1-7

• Mg and O
• MgO
• Mg and MgO
• O and MgO

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

What are the products of the chemical reaction pictured?

• CH₄ and CO₂

• CH₄ and O₂

• CO₂ and 2 H₂O

• O₂ and H₂O

This is the decomposition reaction of hydrogen peroxide. According to the law of conservation of mass, if you start with 40g of hydrogen peroxide you should end up with _____g of water and oxygen combined.

• 10

• 20

• 30

• 40

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The Law of Conservation of Mass States

• Energy cannot be created nor destroyed, it can only change form.

• Mass cannot be created nor destroyed, it can only change form.

• Mass can be created or destroyed, it cannot change form.

Tags

NGSS.MS-PS1-5

Which of the following are examples of physical changes? (Select two answers)

• Change in shape

• Phase change

• Bubbles form

• A new substance is formed

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

Example: H₂

• Coefficient

• Atom

• Subscript

• Equation

What is the number before a chemical formula called?

Example: 2H₂ + O₂ ---> 2H₂O

• Coefficient

• Atom

• Subscript

• Equation

Which of the following examples shows that a chemical reaction has occurred? 

• A rock breaks into smaller pieces when it is struck with a hammer.
• Rust forms on a hammer that has been left outside to long. 
• A cup of water turns pink when a few drops of red food coloring are added. 
• A solid is formed when heat is removed from a sample of water. 

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5