Section 1: Composition of Matter

Warm-up: Think of that air you are breathing in right now. What are some components of air? Why might air be referred to as a mixture?

Learning Goals Define substances and mixtures. Identify elements and compounds. Compare and contrast solutions, colloids, and suspensions.

Matter Matter: anything that has mass and takes up space All matter can be divided into substances and mixtures.

Substances Substances: type of matter with a fixed composition can be either elements or compounds.

Elements Elements: substance built from all atoms of the same identity; cannot be broken down into simpler parts Examples: Hydrogen (H), oxygen (O), carbon (C)

Elements All elements are listed on the periodic table. There are about 90 naturally occurring elements. Approximately 20 have been made in laboratories.

Compounds Compounds: substance in which two or more atoms are combined in a fixed proportion

Compounds Common examples: water (H2O) or sugar (C6H12O6)

Mixtures Mixture: material made of two or more substances that can be separated by physical means Mixtures can be heterogeneous or homogeneous

Heterogeneous Mixtures Heterogeneous mixture: a mixture in which the different materials can be distinguished easily

Heterogeneous Mixtures Examples: salad, granite, dry soup mix

Homogeneous Mixtures Homogeneous mixture: contains two or more gaseous, liquid, or solid substances blended evenly throughout Examples: vinegar (acetic acid and water), iced tea, fog, smoke

Homogenous Mixtures Homogeneous mixtures can be described as solutions or colloids

Solutions Solution: homogeneous mixture with particles so small that they cannot be seen with a microscope and will never settle to the bottom of the container Examples: lemonade, salt water

Solutions Made up of two parts: solute (what is dissolved) solvent (what does the dissolving)

Colloids Colloids: type of mixture with particles that are larger than those in solutions but are not heavy enough to settle out Examples: paint, fog, smoke

Colloids Colloids are detected using the Tyndall effect where you pass light through the substance. The particles in the colloid will scatter the light.

Suspensions Some mixtures are neither solutions nor colloids Suspension: heterogeneous mixture containing a liquid in which visible particles settle. Examples: pond water, Italian dressing

Suspensions

Check-in: Why might it be easy to confuse a compound and a homogeneous mixture?