Chemistry

What kind of change is a phase change?

• Physical - it's still the same substance
• chemical - it's made of chemicals 

What kind of change is a phase change?

• Physical - it's still the same substance
• chemical - it's made of chemicals 

A chemical change happens when...

• a substance is changed at the atomic level 
• bonds are broken and formed 
• a new substance is made
• all of the above! 

A catalyst  

• is added to a reaction to make it slow down 
• breaks apart and is changed 
• provides an energetic short cut to the products 

Chemical Formulas ...

• are written in alphabetical order 
• represent the destruction or creation of atoms 
• represent how atoms are arranged in a chemical reaction 

The compounds or elements present at the end of a reaction 

• reactants
• catalyst
• products
• energy 

The compounds and elements that are present at the beginning of a reaction:

• reactants
• catalyst
• products
• energy 

Which of the following reactions is a combustion reaction ? 

• MgCO3 + O2 → MgO + CO2  
• C3H8 + 5O2 → 3CO2 + 4H2O 
  
• 6CO2 + 6H2O → C6H12O6 + 6O2 
• 6CO2 + 6H2O → C6H12O6 + 6O2 

What is the law of Conservation of Mass?

• A measure of how much mass is created or destroyed. 
• Mass can neither be created nor destroyed during a chemical reaction. 

Explain this graph

• A catalyst is used to speed up the reaction rate
• The catalyst provides a short cut to the products
• The red line shows how the catalyst saves energy 
• All of these choices