Chem 1 Unit 1 Review Guide _KEY

In-Depth Notes Based on Objectives

Objective #1: Hypothesis Formation

Hypothesis Development

• Formulate a hypothesis that indicates the relationship between the independent and dependent variables.

  • Example: In a study assessing jazz music’s impact on sleep, the hypothesis states that listening to jazz while sleeping results in longer sleep duration.

Experiment Design

• Two groups created for the study:

  • Control Group: Slept in silence

  • Experimental Group: Slept while listening to jazz music

• Independent Variable: Jazz music

• Dependent Variable: Sleep duration

Objective #2: Definition and Classification of Matter

Matter

• Defined as the substance that occupies space and possesses mass. Matter can be:

  • A single substance (e.g., water)

  • A mixture (e.g., air)

Properties of Matter

• Physical Properties: Observable characteristics without altering composition (e.g., color, melting point).

• Chemical Properties: Characteristics that indicate how a substance reacts with other substances (e.g., reactivity with water).

Changes of Matter

• Physical Change: Change that does not affect the chemical composition (e.g., melting ice).

• Chemical Change: Change that involves a transformation in chemical composition (e.g., rusting).

Objective #3: Phases of Matter

Comparison of Phases

Key Questions

• Which state has the strongest attraction? (Solid)

• Which state has the most energy? (Gas)

• Which state maintains a fixed volume but has an indefinite shape? (Liquid)

Objective #4: Classification of Matter

Classification Categories

• Element: A pure substance made of only one type of atom.

• Compound: A pure substance made of two or more elements that are chemically combined.

• Homogeneous Mixture: Mixture with indistinguishable parts (uniform composition).

• Heterogeneous Mixture: Mixture with distinguishable parts (non-uniform composition).

Objective #5: Scientific Notation Conversion

Scientific Notation Structure

• Format: N x 10^x, where N is between 1 and 10.

  • Examples:

    • 93,000,000 = 9.3 x 10^7

    • 270,000 = 2.7 x 10^5

Conversion Practice

• 625,000 = 6.25 x 10^5

• 0.004730 = 4.73 x 10^-3

Objective #6: Amounts of Substances and Metric Prefixes

Comparison Using Metric Prefixes

• 1 km > 10 m

• 100,000 mm < 10 km

Common Metric Conversions

• Convert 12.0 g to mg: 12,000 mg

Objective #10: Percent Error Calculation

Formula for Percent Error

• Percent Error = |Accepted Value - Experimental Value| / Accepted Value x 100

Examples

• Comparison of boiling point of ethyl alcohol: |80 - 75| x 100 = 6%

• Density measurement comparison for experimental and accepted values.

Objective #11: Accuracy vs. Precision

Definitions

• Accuracy: Closeness of a measurement to the accepted value.

• Precision: Reproducibility and consistency of measurements.

Objective #12: Estimation and Significant Figures

Significant Figures Rule

• Non-zero digits are significant.

• Leading zeros are not significant.

• Trailing zeros are significant only when a decimal point is present.

Objective #18: Density Calculations

Density Formula

• Formula: Density = Mass / Volume

• Properties: Density is an intensive property and does not depend on the quantity of the material.

Practice Problems

• Calculate density using given mass and volume.

• Identify unknown substances based on density calculations.