science (balancing)

• A chemical reaction is a process in which the properties of the original substance change into new substances with different physical and chemical properties
• Examples of chemical reactions

  • Fireworks
  • Nail or any metal
• Physical reaction/change


  Melting of ice into water, freezing of water into ice, crumpling of paper
• Distinguishing factor between chemical and physical reactions

  In a chemical reaction, there is a change in the compounds, not just the elements
• Evidences of a chemical reaction

  • Change of color
  • Formation of gas
  • Temperature change
  • Change in smell
  • Formation of precipitate
• Reactant


  Substance or group of substances that enter a chemical reaction
• Product


  Substance or group of substances that are produced in a chemical reaction
• Examples of chemical equations

  • Photosynthesis: Carbon dioxide + Water → Glucose + Oxygen gas
  • Carbonic acid breakdown: Carbonic acid → Carbon dioxide + Water
  • Antacid reaction: Sodium bicarbonate + Hydrochloric acid → Sodium chloride + Carbon dioxide + Water
• Coefficient


  Whole number in front of a chemical formula
• Subscript


  Number written below an element in a chemical formula
• Balancing a chemical equation

  1. Add coefficients to balance the number of atoms on each side

  2. Ensure the total mass of reactants equals the total mass of products
• The law of conservation of mass states that matter is neither created nor destroyed in any chemical reaction
• the total mass of the reactants must be equal to the total mass of the products
• In physical change, there are changes in their physical appearance, but the identity remains the same.
• chemical reaction is the process where a material is transformed into a new one, possessing a new composition
• there are two parts of a chemical equation, the reactants and the products.
• Reactants are the substances before reaction and written on the left side of the chemical equation.
• Products are the substances resulting from the reaction and presented at the right side of the chemical equation.
• The reactants and products are separated by an arrow
• + indicates that the substances are added or mixed
• → means “yields”, “makes”, “produces”, “forms” separates the reactants from the products.
• ↓ means that a precipitate is formed.
• ↑ indicates that a gas has evolved.
• (s) designates that the reactants or products are in solid form
• (l) designates that the reactants or products are in liquid form
• (g) designates that the reactants or products are in gas form.
• (aq) designates an aqueous solution; the substance is dissolved in water.
• Combination or Synthesis - a reaction when two or more elements combine to form a single product.
• Decomposition - a single reactant breaks down into simpler ones. It is the opposite of combination reaction.
• Single Displacement (Replacement) – A substance; it can be an element or a compound; capable of replacing one of the atoms of a given compound.
• Double Displacement (Replacement) – a reaction in which ions get exchanged between two reactants, resulting to the formation of a new compound.
• Combustion (Burning) Reaction – a reaction wherein oxygen gas combines with a hydrocarbon; a compound containing carbon and hydrogen atoms; forming carbon dioxide and water as the products.
• Acid-Base Reaction or Neutralization Reaction - special kind of double displacement reaction that takes place when an acid and a base react. In general, the products of this reaction are salt and water.
• The law of conservation of mass is a scientific law popularized and systematized by the 18th-century French chemist Antoine Lavoisier.
• According to this law, matter cannot be created nor destroyed— it can only be changed.
• escapes as a gas happens when some of the mass of a substance formed bubbles during a chemical reaction
• the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.
• reactant - left
• product - right
• chemical equation- a shorthand notation that represents substances undergoing chemical reactions