Chapter 1: Matter & Measurement – General Chemistry Study Notes

Matter & Measurement

Introduction to Chemistry

Chemistry is the scientific study of matter and the changes it undergoes. It explores the composition, structure, properties, and transformations of substances.

• Matter: Anything that has mass and occupies volume.

• Mass: A measure of the amount of matter in an object, typically quantified in grams (g), kilograms (kg), etc. Note: Mass is different from weight, which is the force of gravity acting on mass.

• Volume: The amount of three-dimensional space a substance occupies, measured in liters (L), milliliters (mL), or cubic centimeters (cm3).

Formula for Volume (rectangular object):

• $\text{Volume} = \text{Length} \times \text{Width} \times \text{Height}$

• 1 mL = 1 cm3

Density

Density is a physical property that describes the mass of a substance per unit volume. It is useful for identifying substances and predicting their behavior in mixtures.

• Common units: g/cm3 or g/mL

• Formula: $\text{Density} = \frac{\text{mass}}{\text{volume}}$

Examples:

• Ex 1: A piece of wood has a mass of 457.2 g and a volume of 82.03 cm3. Density calculation: $d = \frac{457.2}{82.03} = 5.574\ \text{g/cm}^3$

• Ex 2: Mercury has a density of 13.54 g/mL. If its mass is 100.0 g, its volume is $v = \frac{100.0}{13.54} = 7.386\ \text{mL} = 0.007386\ \text{L}$

Classification of Matter

Types of Matter

Matter can be classified based on its composition and properties. The main categories are mixtures and pure substances.

Type	Can be physically separated?	Uniform composition?	Can be chemically decomposed?
Homogeneous Mixture (Solution)	Yes	Yes	No
Heterogeneous Mixture	Yes	No	No
Compound	No	Yes	Yes
Element	No	Yes	No

Mixtures

• Mixture: A combination of two or more substances that retain their own identities.

• Homogeneous Mixture (Solution): The composition is uniform throughout. Examples: salt water, soft drinks.

• Heterogeneous Mixture: The composition is not uniform throughout. Examples: concrete mix, salad, pizza.

Pure Substances

• Substance: A form of matter with distinct properties and definite composition.

• Element: A substance that cannot be separated into simpler substances by chemical means.

• Compound: A substance composed of atoms of two or more elements chemically combined in a fixed proportion.

Properties of Matter

Intensive and Extensive Properties

Properties of matter can be classified based on whether they depend on the amount of substance present.

• Intensive Property: Does not depend on the amount of matter present. Examples: density, color, temperature.

• Extensive Property: Depends on the amount of matter present. Examples: length, mass, volume.

Physical and Chemical Changes

Physical Change

A physical change alters the form of a substance but does not change its chemical composition.

• Examples: salt dissolving in water, melting of ice.

Chemical Change

A chemical change results in the formation of a new substance with different properties and composition due to a chemical reaction.

• Example: Hydrogen reacts with oxygen to form water.

States of Matter

Solid, Liquid, and Gas

Matter exists in three primary states, each with distinct physical properties.

• Solid: Has a definite shape and volume; particles are closely packed and cannot flow.

• Liquid: Has a definite volume but takes the shape of its container; particles can flow.

• Gas: Has neither definite shape nor volume; particles are far apart and can flow freely.