Cambios químicos

Which of these changes are chemical changes?

• Cutting a paper.

• Boiling water.

• The oxidation of an appel.

• Respiration.

The main difference between a physical and a chemical change is that...

• in a chemical change the color changes but in a physical change the color never changes.

• new substances are produced in a physical change but not in a chemical change.

• in a chemical change gases are emitted.

• new substances are produced in a chemical change but not in a physical change.

What changes can you appreciate in this chemical change:

• Change in color.

• Change in odor.

• Change in temperature.

• Production of light.

• Formation of a solid.

A chemical change is the same than a chemical reaction.

• True.

• False.

Which are the reactants in the following chemical reaction:

Methane reacts with oxygen to produce water and carbon dioxide.

• Methane.

• Water.

• Oxygen.

• Carbon dioxide.

Which are the products in the following chemical reaction: Sodium reacts with hydrogen chloride to produce sodium chloride and hydrogen.

• Sodium chloride.

• Hydrogen chloride.

• Hydrogen.

• Sodium.

New substances are produced in a chemical reaction because...

• new atoms are created.

• the atoms wich form the reactants reorder and join in a different way.

• the atoms wich form the reactants disappear.

A chemical equation is...

• the same than a chemical reaction.

• a representation of a chemical reaction.

• the same than a chemical change.

The law of conservation of mass was proposed by...

• Mendeleiev.

• Newton.

• Lavoisier.

• Einstein.

According to the law of conservation of mass...

• chemical reactions create matter.

• chemcial reactions destroy matter.

• chemcial reactions transform matter.

• The mass of the reactants is equal to the mass of the products.