Law of Conservation of Mass

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

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

Which of these is not a chemical reaction?

• Burning of wood
• Milk going bad
• Mixing vinegar and baking soda
• Melting of ice

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

• 4g
• 5g
• 9g
• 14g

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

Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?

• The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
• Bubbles were produced during the reaction, which meant that a gas was being produced.
• The plastic bag did not change in any way, indicating that it was not involved in the reaction.
• The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.

Suppose a reaction were to happen in an open container in a lab.  During the reaction, the scientist observes the chemicals bubble, and produce a gas.   During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g.  Explain what happened.  

• His chemical reaction defied the law of conservation of mass
• The product destroyed mass during the reaction
• The reactants created matter during the reaction
• The gas that was produced was not able to be weighed since the container was open.  

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

Think of an example of the Law of Conservation of Mass in your everyday life. Don't limit your answers to chemical reactions, any example of a process where the mass doesn't change will do.