CFE Review: Law of Conservation of Mass and Energy

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

What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?

• They both will weigh the same
• The product always weighs more than the reactant
• The reactant will weigh more than the product
• They both will loose mass after the reaction

Since gasses weigh nothing, when they are produced in a reaction they do not have to be accounted for.  

• True
• False

Which are chemical changes

• Iron rusting 
• Glass breaking
• Clothing ripping
• Hair cut

Can matter be created or destroyed?

• Yes, it can be created.
• Yes, it can be destroyed.
• No, matter is always conserved
• None of these

The mass after a physical change, such as ice melting into water, stays the same

• True
• False

Evidence of a chemical reaction include:

• Phase change
• No new substance
• Bubbles forming
• Shape change

10 g of a solid chemical reacts with a 10 g of a liquid chemical, the reaction bubbles and changes the color of the liquid.  The colored liquid weighs 13 g, what can be concluded?

• The gas produced from the bubbles weighed 5 g
• The bubbles were evidence of 7 g of matter being destroyed
• The gas produced weighed 7 g
• The gas produced weighed 13 g

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed 
• Energy cannot be created or destroyed, it can only transformed
• Energy can't be created, destroyed or transformed

Which energy transformation below matches?
Animals eating food?

• electrical to potential
• chemical to kinetic
• potential to chemical