Chemical Reactions

Identify: Which is a sign of a chemical reaction?

• Chemical properties change.

• Physical properties change.

• A gas forms.

• A solid forms.

Analyze: Using the periodic table, what atoms are present in the following chemical reaction?

CO2+NaOH→NaHCO3

• sodium, oxygen, hydrogen, cobalt

• 
  sodium, oxygen, hydrogen, carbon

• nitrogen, hydrogen, oxygen, cobalt

• nitrogen, hydrogen, oxygen, carbon

In the chemical equation HCl(acid)+NaOH(base)→H2O+NaCl, what atoms are present and what is produced by the reaction?

• Atoms of hydrogen, chlorine, sodium, and oxygen are present. When HCl and NaOH are combined they produce water and salt. This is because they neutralize the properties of each other.

• Atoms of hydrogen, chlorine, nitrogen, and oxygen are present. When HCl and NaOH are combined they produce water and salt. This is because they neutralize the properties of each other.

• Atoms of hydrogen, chlorine, sodium, and oxygen are present. When HCl and NaOH are combined they produce water and salt. This is because the properties of the acid take over.

• Atoms of hydrogen, chlorine, sodium, and oxygen are present. When HCl and NaOH are combined they produce water and salt. This is because the properties of the base take over.

Relate: Examine the chemical equation for photosynthesis. Which statement correctly describes how mass is conserved during this chemical reaction?

6CO2+6H2O→C6H12O6+6O2

carbon dioxide + water → sugar + oxygen gas

• Atoms disappear, causing the mass of the products to be less than the mass of the reactants.

• The atoms rearrange, causing the mass of the products to equal the mass of the reactants.

• The atoms change into new atoms, causing the mass of the products to equal the mass of the reactants.

• No changes occur, causing the mass of the products to equal the mass of the reactants.

Two solutions are mixed and react to produce AgCl. The chemical reaction is shown by the balanced equation.

AgNO3+LiCl→AgCl+LiNO3

What happens to the total mass as the reaction takes place?

• The mass increased.

• The mass decreased.

• The mass stayed the same.

• The mass first increased and then decreased.

What atoms are involved in this chemical reaction?

CaCO3→CaO+CO2

• calcium, cobalt, and oxygen

• calcium, carbon, and oxygen

• calcium, carbon, and cobalt

• carbon and oxygen

What is a Reactant?

• The end result of a chemical reaction.

• The arrow that separates the product from the reactant.

• The number to the lower right of an element that shows the number of atoms.

• The substance changed in a chemical reaction.

What is an example of a chemical change?

• Tearing paper

• Dissolving salt in water

• Melting ice

• Burning wood

• 3

• 4

• 7

• 12

• 4

• 12

• 9

• 24