Matter, Energy, and Measurement: GOB Chemistry Study Notes

Chapter 1: Matter, Energy, and Measurement

Matter

Matter is anything that has mass and takes up space. All physical substances are forms of matter.

• Examples: Water, air, rocks, and living organisms are all matter.

Chemistry

Chemistry is the science that deals with matter, its structure and properties, and the transformations from one form of matter to another.

• Chemical change (chemical reaction): Occurs when substances are used up (disappear) and others are formed (e.g., burning paper or cooking an egg).

• Physical change: The identities of the substances do not change (e.g., evaporation of water or melting of ice).

Scientific Method

The scientific method is a systematic approach to investigation and discovery in science.

• Fact: A statement based on direct experience.

• Hypothesis: A proposed statement, without actual proof, to explain facts and their relationships.

• Theory: A hypothesis that has been supported by evidence and is widely accepted.

Exponential Notation

Exponential notation is a way to handle large and small numbers using powers of 10.

• Example: $5640000 = 5.64 \times 10^6$

• Example: $0.00000000732 = 7.32 \times 10^{-9}$

Units and Conversion of Units

Measurement consists of two parts: a number and a unit. A number without a unit is meaningless.

Metric System of Units and SI (International System of Units)

The metric system uses base units for each kind of measurement, and other units are related to the base unit by powers of 10.

• Base unit for length: meter (m)

• Base unit for volume: liter (L)

• Base unit for mass: gram (g)

• Base unit for time: second (s)

Prefix (Symbol)	Value
giga (G)	$10^9$
mega (M)	$10^6$
kilo (k)	$10^3$
deci (d)	$10^{-1}$
centi (c)	$10^{-2}$
milli (m)	$10^{-3}$
micro (μ)	$10^{-6}$
nano (n)	$10^{-9}$

• 1 kilometer (km) = 1000 meters (m)

• 1 centimeter (cm) = 0.01 meters (m)

• 1 liter (L) = 1000 milliliters (mL) = 1000 cm3

• 1 kilogram (kg) = 1000 grams (g)

• 1 gram (g) = 1000 milligrams (mg)

• 3600 seconds (s) = 1 hour (h)

English System of Units

Used in the United States (pounds, miles, gallons, etc.).

Temperature

• Fahrenheit (°F): Used in the English system.

• Celsius (°C): Used in the metric system.

• Kelvin (K): Used in SI; absolute scale.

Conversion formulas:

• $^{\circ}\mathrm{F} = 1.8 \times ^{\circ}\mathrm{C} + 32$

• $^{\circ}\mathrm{C} = \frac{^{\circ}\mathrm{F} - 32}{1.8}$

• $\mathrm{K} = ^{\circ}\mathrm{C} + 273$

• $^{\circ}\mathrm{C} = \mathrm{K} - 273$

Factor-Label Method (Dimensional Analysis)

The factor-label method is a systematic way to convert one unit to another using conversion factors.

• Example: $84\,\text{in} = ?\,\text{cm}$ $84\,\text{in} \times \frac{2.54\,\text{cm}}{1\,\text{in}} = 213.36\,\text{cm}$

• Example: $25\,\text{km/h} = ?\,\text{mi/s}$ $25\,\text{km/h} \times \frac{1\,\text{mi}}{1.609\,\text{km}} \times \frac{1\,\text{h}}{3600\,\text{s}} = 0.0043\,\text{mi/s}$

States of Matter

Matter exists in three primary states: gas, liquid, and solid.

• Gases: No definite shape or volume; expand to fill their container; highly compressible.

• Liquids: Definite volume but no definite shape; slightly compressible.

• Solids: Definite shape and volume; incompressible.

Note: The state of a substance depends on temperature and pressure. Physical changes (e.g., melting, boiling) do not change the chemical identity of a substance.

Density and Specific Gravity

Density (d): The mass per unit volume of a substance. For gases, density is often expressed in g/L.

• Formula: $d = \frac{m}{v}$ where $m$ = mass, $v$ = volume

• Note: Density usually decreases with increasing temperature.

Specific Gravity (SG): The ratio of the density of a substance to the density of water. It is dimensionless and often measured with a hydrometer.

• Formula: $\text{SG} = \frac{d_{\text{substance}}}{d_{\text{water}}}$

Energy

Energy is the capacity to do work or produce heat. It exists in various forms:

• Kinetic Energy (KE): Energy of motion. Any moving object has kinetic energy. Formula: $KE = \frac{1}{2}mv^2$ where $m$ = mass, $v$ = velocity

• Potential Energy (PE): Stored energy due to position or composition.

• Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Heat and Specific Heat

Heat is the energy transferred due to temperature difference. The amount of heat required to raise the temperature of 1 g of water by 1°C is called a calorie (cal).

• 1 kcal = 1000 cal

• SI unit of heat: Joule (J)

Specific Heat (SH)

Specific heat is the amount of heat necessary to raise the temperature of 1 g of a substance by 1°C. Each substance has its own specific heat.

• Unit: cal/g·°C

• Formula: $\text{Amount of heat} = \text{SH} \times \text{mass} \times (T_2 - T_1)$ where $T_1$ = initial temperature, $T_2$ = final temperature