CHEM110: Intro to Matter & Scientific Method

• CHEM110 covers quantitative chemistry.

Introduction to Matter

• Chemistry studies matter, which has mass and occupies space, and its interactions.
• Matter is composed of atoms, and there are approximately 100 types of atoms called elements.
• Atoms combine to form molecules and more complex structures, giving materials different properties.
• Understanding matter's structure helps understand its reactivity and properties.
• Chemists can create new materials from molecules and atoms using standard chemical reactions.

Scientific Method

• Science relies on observations.
• Experiments observe natural phenomena in a controlled and repeatable manner, allowing for conclusions.
• A hypothesis is a tentative explanation of a regularity, which can become a theory if it passes several tests.
• A law is a concise statement or equation about a fundamental relationship or regularity in nature.

Physical States and Changes of Matter

• Matter exists in solid, liquid, and gas states.
• Solids have a rigid shape, fixed volume and are almost incompressible.
• Liquids are relatively incompressible fluids with a fixed volume but without a defined shape.
• Gases are easily compressible fluids that can fit into almost any shape and size container.
• Physical change alters the form of matter without changing its chemical identity.
• Chemical change (reaction) transforms matter into a new kind with different properties.

Classifying Matter

• Matter is classified based via its physical state and chemical composition.

Chemical Constitution

• Substances cannot be separated into other kinds of matter by any physical process.
• Elements, of which there are 116 known, cannot be broken down into simpler substances by chemical means.
• Most substances are compounds, composed of two or more chemically combined elements.
• Pure compounds always contain constant proportions of elements by mass and can be broken down into their constituent elements.
• Mixtures can be separated by physical means like distillation, precipitation, or chromatography.
• Unlike pure compounds, Mixtures have variable composition.
• Heterogeneous mixtures have physically distinct parts, like iron filings and sulphur powder, or carbonated water.
• Homogeneous mixtures (solutions) have uniform properties, like sugar dissolved in water or black coffee; alloys are examples.
• A phase is a distinctive part of a heterogeneous sample, and a homogeneous sample always consists of only a single phase.

Relationships Between Matter

• Matter can be divided into substances and mixtures
• Substances can be either elements or compounds
• Mixtures can be either homogenous or heterogenous.
• Intensive properties are independent of the amount of substance present, examples being density, boiling point, and color
• Extensive properties are dependent of the amount of substance present, examples being mass, volume, and energy.

Chemical vs Physical Changes

• Chemical changes result in creating new substances.
• The new substances formed via chemical changes have different properties from the original ones.
• Chemical changes include combustion, oxidation, and decomposition.
• During a chemical reaction, reacting substances transform into new substances.
• Physical changes alter matter without changing its chemical composition.
• A substance maintains its chemical composition after a physical change.
• Physical changes include changes of state (solid, liquid, gas), temperature, and volume.

Example of Changes

• Reacting zinc metal with hydrochloric acid to produce zinc(II) chloride and hydrogen gas is a chemical change.
• Combusting hydrogen gas to produce water is a chemical change.
• Dissolving zinc(II) chloride and freezing liquid water are physical changes.