Chemistry: Acids, Bases, and pH Scale

Unknown Liquids Data

• Students investigated whether unknown liquids were acids or bases
• The dependent variable was the color change of litmus paper
• The independent variable was the pH of the unknown liquid
• Litmus paper indicator was a constant

Compounds, Elements and Mixtures

• A compound is a pure substance made of two or more elements bonded together
• An element is the purest form of matter that cannot be broken down further
• A mixture is a combination of two or more substances that are not chemically bonded

Examples of Elements, Compounds, or Mixtures

• H₂ - element
• H₂O - compound
• Air - mixture
• C₆H₁₂O₆ - compound

pH Scale

• Substances were placed on a pH scale.
• Distilled water (pH 7.0) - located on spot B
• Battery Acid (pH 1.5) - located on spot A
• Milk (pH 8.5) - located on spot C
• Sodium Hydroxide (pH 13.0) - located on spot D

Acid Properties

• Sour taste
• Rough
• Conducts electricity
• Reacts with bases
• pH less than 7

Base Properties

• Bitter taste
• Slippery
• Conducts electricity
• Reacts with acids
• pH greater than 7

Atom Inventory

• Data was given to conduct an atom inventory for some molecules.
• The number and type of atoms in a molecule is identified.

Chemical Equation

• 6CO₂ + 6H₂O → C₆H₁₂O₆ + O₂
• Reactants: 6CO₂ and 6H₂O
• Products: C₆H₁₂O₆ and O₂
• CH₄ + 2O₂ → CO₂ +2H₂O is a balanced equation for combustion of methane
• C₃H₈ + 5O₂ → 4H₂O +3CO₂ is a balanced equation

Law of Conservation of Mass

• Matter cannot be created or destroyed
• The mass of the reactants will equal the mass of the products in a closed system.
• 34 g C₆H₅COOH + 9 g O₂ → 18 g CO₂ + 13 g H₂O represents that the mass of reactants equals the mass of products

Physical and Chemical Changes

• Examples of physical changes: ice melting, salt dissolving, changing color of water, cutting paper
• Examples of chemical changes: burning wood, mixing baking soda and vinegar, iron rusting, copper turning green
• Clues to chemical changes: unexpected color change; gas formation (bubbles), precipitate (solid) formation, change in temperature

Types of Reactions

• Exothermic reactions: release heat to surroundings; feel warm to touch
• Endothermic reactions: absorb heat from surroundings; feel cold to touch

pH Values

• pH range for acids: 0-6.9
• pH range for bases: 7.1 and above
• pH of a neutral substance: 7

Metals and Nonmetals

• Metals are elements left of the staircase on the periodic table
• Properties of metals include: luster, good conductors, ductile, malleable, solid at room temperature
• Nonmetals generally are right on the periodic table, have dull appearances that are poor conductors, brittle that are not ductile or malleable, often gases at room temperate.

Bonds

• Ionic bonds: form between metals and nonmetals; electrons are transferred
• Covalent bonds: form between nonmetals and nonmetals; electrons are shared

Ions and Isotopes

• Ion: a charged atom
• Isotopes: atoms with the same number of protons, but different numbers of neutrons

This quiz explores the properties of acids and bases, the classification of substances as elements, compounds, or mixtures, and their behavior on the pH scale. Students will apply their understanding by investigating unknown liquids and interpreting litmus paper color changes. Dive into the essential concepts of chemistry with this engaging quiz!