Law of Conservation of Energy and Matter

According to the law of conservation of energy, the total amount of energy in the universe is

• increasing
• decreasing
• constant

In an exothermic chemical reaction, the energy gained by the surroundings must be what compared to the energy lost by the reaction?

• equal to
• greater than
• less than

In an endothermic chemical reaction, the energy lost from the surroundings must be what compared to the energy gained by the reaction?

• equal to
• greater than
• less than

Which statement best describes matter and energy?

• Matter is different from energy because matter is always destroyed in a chemical reaction.
• Matter is similar to energy because matter is always conserved in a chemical reaction.
• Matter is similar to energy because matter is always created in a chemical reaction.

In an exothermic chemical reaction, the energy that is given off by the reaction comes from

• the surroundings
• an external heat source
• stored energy in the chemical bonds of the reactants

What happens to the reactants when a chemical reaction takes place?

• They all remain intact
• They are destroyed, or consumed by the reaction
• Their chemical bonds are broken and rearranged

The bond enthalpy value for a carbon to hydrogen bond is 413 kJ. What does this mean?

• It takes 413 kJ of energy to break a carbon to hydrogen bond.
• The formation of a carbon to hydrogen bond releases 413 kJ of energy.
• Both of the above

When chemical bonds are formed, energy isQuestion options:

• stored in the bond
• released from the bond
• not needed in the bond

In the chemical formula 3NH₄, how many total atoms of nitrogen (N) are there?

• 1
• 3
• 12

In the chemical formula 3NH₄, how many total atoms of hydrogen (H) are there?

• 1
• 4
• 12