Chapter 2 Matter

Overview Learn about the composition of matter Learn the difference between elements and compounds Distinguish between physical and chemical properties and changes Distinguish between mixtures and pure substances Learn 2 methods of separating mixtures

Did you ever wonder?... How do plants grow & why are they green? Why is the sun hot? Why does a hot dog get hot in a microwave? Why does wood burn and rocks do not? How does soap work? Why does pop fizz? What’s happening when iron rusts? Why doesn’t aluminum foil rust? How does a hair permanent work?

The Particulate Nature of Matter Matter: the “stuff” the universe is composed of Has mass and occupies space Comes in many forms: the stars, your chair, brain tissue Composed of tiny particles called atoms Scanning tunneling microscope produces images of atoms Can’t see with naked eye, similar to looking at beach from far away; can only see sand particles when you get close

Elements and Compounds Atoms: all matter is composed of these tiny particles Over 100 different atoms Similar to words, all made from 26 different letters All matter made from about 100 different atoms Compounds: substances made by bonding atoms together in specific ways Contain 2 or more different types of atoms Same throughout Molecule: made up of atoms that are “stuck” together

Atom Combinations

Elements Some atoms can combine with like atoms to form molecules: H2 & O2 Carbon bonds forming large groups Elements: substances that contain only one type of atom Compound: always contains atoms of different elements (water = H2O)

Top Ten

Figure 2.5: The three forms of the element carbon: Diamond.

Figure 2.5: The three forms of the element carbon: Graphite.

Figure 2.5: The three forms of the element carbon: Buckminsterfullerene.

The States of Matter

Figure 2. 7: The three states of water: Solid Figure 2.7: The three states of water: Solid. Solids: Rigid; have a fixed shape and volume

Figure 2.7: The three states of water: Liquid Liquid: has a definite volume but takes the shape of its container

Figure 2. 7: The three states of water: Gas Figure 2.7: The three states of water: Gas. Gas: has no fixed volume or shape; uniformly fills any container

Physical and Chemical Properties and Changes Physical Properties: Odor, color, volume, state, density, melting point, and boiling point Chemical properties: refer to a substances ability to form new substances Examples: wood burning, rusting of steel, digestion of food, growth of grass Given substance changes to a fundamentally different substance or substances

Chemical vs. Physical change in water Physical changes solid → liquid → gas Change of state: H2O molecules still present Chemical change = electrolysis water changed into different substances (water decomposes to hydrogen & oxygen)

Electrolysis, the decomposition of water by an electric current, is a chemical process.

Physical & Chemical Changes Physical change involves a change in one or more physical properties, but no change in fundamental components of substance. Most common are changes in state. Chemical change involves a change in the fundamental components of the substance. Chemical changes are called reactions.

Mixtures and Pure Substances Mixture: something that has variable composition Examples: soda, coffee, tap water, air Composition of mixtures varies, but composition of compounds is always the same Composition depends on how much of each component is used when mixture is formed Can be separated into pure substances: elements and/or compounds

The composition of air.

Chart examining each substance of air.

Mixtures: Alloys Alloys: mixtures of metals Many gold alloys: mixture of gold, copper, and silver They are not compounds! (like water) Composition varies

Figure 2.10: Twenty-four-karat gold is an element Eighteen-karat gold is an alloy. Fourteen-karat gold is an alloy.

Homogeneous and Heterogeneous Homogeneous mixture is the same throughout, & also called a solution Examples: salt water, air, brass (mixture of copper and zinc) Heterogeneous mixture contains regions that have different properties from other regions Examples: sand/water mixture, rocky road ice cream, chocolate chip cookie dough

Representation of H2O molecules.

Distillation: Separation Process Boil water (or other liquid) Vaporizes (turns into gas = steam) Condense (cool steam in tube) – turns back to liquid Minerals are left behind Pure water collected Physical change

The solution is boiled and steam is driven off.

Salt remains after all water is boiled off.

No chemical change occurs when salt water is distilled.

Filtration: Separation Process Pour mixture onto a mesh, such as filter paper Liquid passes through, solid is left behind on filter paper

Filtration separates a liquid from a solid.

Separation of a sand-saltwater mixture.

Pure Substances Pure substances are either elements or compounds Always have same chemical and physical properties

The organization of matter.

Setup to boil water.