Exam 1 Study Guide: CHM 130 (Chapters 1-3) – Chemistry in Our Lives, Measurements, Matter & Energy

Exam 1 Study Guide: CHM 130

Chapters 1-3 Overview

This study guide covers foundational topics in chemistry, focusing on significant figures, measurements, matter, energy, and basic calculations. These concepts are essential for understanding the principles of chemistry and for performing accurate scientific work.

Chemistry in Our Lives

Significant Figures and Calculations

Significant figures are crucial for expressing the precision of measurements and calculations in chemistry.

• Significant Figures: Digits in a measurement that are known with certainty plus one estimated digit.

• Rules: Learn how to round off in addition, subtraction, multiplication, and division.

• Example: When multiplying 2.34 (3 sig figs) by 1.2 (2 sig figs), the answer should have 2 significant figures.

Additional info: In addition/subtraction, the result is rounded to the least number of decimal places; in multiplication/division, to the least number of significant figures.

Chemistry and Measurements

Scientific Notation

Scientific notation is used to express very large or very small numbers efficiently.

• Expressing Numbers: Convert between standard and scientific notation.

• Example: 0.00056 = $5.6 \times 10^{-4}$

Physical/Chemical Changes

Understanding the difference between physical and chemical changes is fundamental in chemistry.

• Physical Change: Change in state or appearance without altering composition (e.g., melting ice).

• Chemical Change: Change that produces new substances (e.g., rusting iron).

• Example: Dissolving sugar in water is a physical change; burning wood is a chemical change.

Temperature Conversions

Temperature can be measured in Celsius, Fahrenheit, and Kelvin. Converting between these units is a common task.

• Formulas:

  • Celsius to Fahrenheit: $F = \frac{9}{5}C + 32$

  • Fahrenheit to Celsius: $C = \frac{5}{9}(F - 32)$

  • Celsius to Kelvin: $K = C + 273.15$

• Example: Convert 25°C to Fahrenheit: $F = \frac{9}{5} \times 25 + 32 = 77°F$

Types of Matter

Matter can be classified as elements, compounds, homogeneous mixtures, or heterogeneous mixtures.

• Element: Pure substance made of one type of atom (e.g., O2).

• Compound: Substance made of two or more elements chemically combined (e.g., H2O).

• Homogeneous Mixture: Uniform composition (e.g., salt water).

• Heterogeneous Mixture: Non-uniform composition (e.g., salad).

Matter and Energy

States of Matter

Matter exists in different states: solid, liquid, and gas. Each state has distinct properties.

• Solid: Definite shape and volume.

• Liquid: Definite volume, no definite shape.

• Gas: No definite shape or volume.

• Example: Water as ice (solid), liquid water, and steam (gas).

Energy Concepts

Energy is the capacity to do work or produce heat. It can be classified as kinetic or potential energy.

• Kinetic Energy: Energy of motion.

• Potential Energy: Stored energy due to position.

• Example: A ball at the top of a hill has potential energy; rolling down, it has kinetic energy.

Density Calculations

Density is a physical property that relates mass and volume.

• Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Example: If mass = 10 g and volume = 2 mL, density = $\frac{10}{2} = 5$ g/mL.

• How to Rearrange: To find mass: $\text{Mass} = \text{Density} \times \text{Volume}$; to find volume: $\text{Volume} = \frac{\text{Mass}}{\text{Density}}$

Unit Conversions

Converting between units is essential for solving chemistry problems.

• Metric Conversions: Use conversion factors to change units (e.g., cm to m, g to kg).

• Example: 100 cm = 1 m; 1 kg = 1000 g.

Calorie and Joule Conversions

Energy can be measured in calories or joules. Understanding their relationship is important in chemistry.

• Conversion: $1 \text{cal} = 4.184 \text{J}$

• Example: 10 cal = $10 \times 4.184 = 41.84$ J

Multi-Step Problems

Some problems require multiple steps and the use of several concepts, such as energy-related calculations.

• Example: Calculate the energy required to heat water from one temperature to another using specific heat capacity.

• Formula: $q = m \times c \times \Delta T$

• Where: $q$ = heat energy, $m$ = mass, $c$ = specific heat, $\Delta T$ = change in temperature.

Additional info: Multi-step problems may combine unit conversions, density, and energy calculations.

Summary Table: Types of Matter

Type	Description	Example
Element	Pure substance, one type of atom	O2, Fe
Compound	Two or more elements chemically combined	H2O, CO2
Homogeneous Mixture	Uniform composition	Salt water, air
Heterogeneous Mixture	Non-uniform composition	Salad, sand and iron filings