LAW OF CONSERVATION OF MASS

What is the law of conservation of mass?

• The amount of matter changes when reacted or changed.
• The mass of all reactants are changed during a physical or chemical change
• The mass of the reactants equals the mass of the products
• The mass of the products is different than the mass of the reactants.

Students react baking soda with vinegar in Coach Moore's class. 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 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 grams when he started, and the product weighed 18 grams. 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 grams of a solid chemical reacts with a 10 grams 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 grams

• The bubbles were evidence of 7 grams of matter being destroyed

• The gas produced weighed 7 grams

• The gas produced weighed 13 grams

Fill in the coefficient for HCl to balance the chemical equation.

Mg + ___ HCl → MgCl₂ + H₂

• 1

• 2

• 3

• 4

During our elephant toothpaste demonstration, heat was produced when the hydrogen peroxide bonds were broken during the decomposition reaction. A chemical reaction that releases heat is called?

• Endothermic

• Exothermic

• Unstable

• Thermodynamic

Students in Coach Moore's class combined baking soda and vinegar in a Ziplock bag. Once the reaction began, students noticed the bag felt cooler to the touch. A chemical reaction or process that absorbs heat from the surroundings is called?

• Endothermic

• Exothermic

• Synthetic

• Unstable

A ______________ is a substance that increases the rate of a reaction without changing any other properties of that reaction

• catalyst

• product

• reactant

• solute

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

How many oxygen atoms are in this chemical formula?

• 6 oxygen atoms
• 2 oxygen atoms
• 3 oxygen atoms
• 4 oxygen atoms