Phy Sci Test

Test Review Overview

  • Key Topics:

    • Chemical and Physical Change

    • Chemical Property and Physical Property

    • Pure Substance

    • Homogenous and Heterogenous Mixtures

Chemical and Physical Changes

  • Chemical Change:

    • Involves the formation of new substances through chemical reactions.

    • Example: Rusting of iron.

  • Physical Change:

    • Does not change the chemical composition of a substance.

    • Example: Melting ice to water.

Properties of Substances

  • Chemical Properties:

    • Describe a substance's ability to undergo changes that transform it into different substances.

    • Example: Flammability.

  • Physical Properties:

    • Can be observed without changing the identity of the substance.

    • Example: Color, melting point.

Pure Substances and Mixtures

  • Pure Substance:

    • Has a uniform and definite composition.

    • Consists of one type of particle.

  • Mixtures:

    • Combination of two or more pure substances that retain their individual properties.

    • Can be classified as homogenous (uniform composition) or heterogeneous (distinct substances visible).

Compounds vs. Mixtures

  • Compound:

    • A substance formed when two or more elements chemically bond.

    • Has a fixed composition and properties.

  • Mixture:

    • A combination of two or more substances where each retains its individual properties.

    • Elements and compounds can exist together without changing their properties.

Density Calculations

  • Density Formula:

    • Density (D) = Mass (m) / Volume (V)

    • Example Calculation: When m = 15g and volume = 0.5 cm x 0.6 cm x 0.7 cm = 0.21 cm³,

    • Density = 15g / 0.21cm³ = 71.4 g/cm³

Specific Heat and Heat Transfer Equations

  • Specific Heat Formula:

    • q = mCΔT

    • Where q = heat absorbed/released, m = mass, C = specific heat, ΔT = change in temperature

  • Endothermic Process:

    • Absorbs heat.

    • Example: Melting of ice.

  • Exothermic Process:

    • Releases heat.

    • Example: Freezing of water.

Key Specific Heat Values

  • Specific Heat Capacities:

    • Water (H₂O) = 4.18 J/g°C

    • Gases = 2.02 J/g°C

    • Solids = 2.06 J/g°C

Thermodynamic Equations

  • Heat Transfer Calculations:

    • ΔHfus (enthalpy of fusion) = 334 J/g

    • ΔHvap (enthalpy of vaporization) = 2260 J/g

Exam Preparation Notes

  • On Test:

    • Familiarize with formulas:

      • MCAT = m·C·ΔT

      • m·ΔHfus = heat of fusion-related calculations

      • m·ΔHvap = heat of vaporization-related calculations

    • Be prepared with numerical examples using the above formulas for various temperature changes.

Examples of Key Concepts:

  • Chemical Change: An example of a chemical change is the process of iron rusting.

  • Physical Change: An illustration of a physical change is the melting of ice into water.

  • Chemical Property: Flammability serves as an example of a chemical property.

  • Physical Property: Observable characteristics like color and melting point represent physical properties.

  • Pure Substance Example: Water (H₂O) is characterized as a pure substance due to its uniform composition.

  • Homogenous Mixture Example: Saltwater is a homogenous mixture with a uniform composition.

  • Heterogeneous Mixture Example: A salad exemplifies a heterogeneous mixture, as its distinct components are visible.

  • Endothermic Process: The melting of ice is an example of an endothermic process, as it absorbs heat.

  • Exothermic Process: Freezing water is an example of an exothermic process, where heat is released.

  • Example Calculation for Density: For a mass of 15g and a volume of 0.21 cm³, the density calculation would yield Density = 15g / 0.21cm³ = 71.4 g/cm³.