Chapter 3: Matter and Energy

 With your partner, decide whether the items on the card are matter or not matter.  Create a list of properties that apply to all items that you consider to be matter.  Place the cards in the appropriate place on the board once you are finished.

 Classify matter as element, compound, or mixture.  Distinguish between heterogeneous and homogeneous mixtures.

 Matter: anything that occupies space and has mass.  Some types of matter, such as steel, water, wood, and plastic, are easily visible to our eyes.  Other types of matter, such as air or microscopic dust, are impossible to see without magnification.

 Matter is ultimately composed of atoms.  Atoms: submicroscopic particles that are the fundamental building blocks of matter.

 In many cases, these atoms are bonded together to form molecules.  Molecules: two or more atoms joined to one another in specific geometric arrangements.

 Recent advances in microscopy have allowed us to image the atoms and molecules that compose matter.

 Scanning tunneling microscope image of nickel atoms  A scanning tunneling microscope (STM) creates an image by scanning a surface with a tip of atomic dimensions. (Source: Reprint Courtesy of International Business Machines Corporation, copyright © International Business Machines Corporation.)

 Scanning tunneling microscope image of a DNA molecule  In this image, the DNA molecule is yellow.  The double-stranded structure of DNA is discernible.

 The common states of matter are solid, liquid, and gas.  Plasma  Bose Einstein Condensate

 Water exists as ice (solid), water (liquid), and steam (gas).  In ice, the water molecules are closely spaced and, although they vibrate, they do not generally move relative to one another.  In liquid water, the water molecules are closely spaced but are free to move around and past each other.  In steam, water molecules are separated by large distances and do not interact significantly with one another.

 In solid matter, atoms or molecules pack close to each other in fixed locations.  Neighboring atoms or molecules in a solid may vibrate or oscillate, but they do not move around each other.  Solids have fixed volume and rigid shape.  Examples: Ice, diamond, quartz, and iron

 Crystalline solid: Atoms or molecules are arranged in geometric patterns with long- range, repeating order.  Examples: salt, diamond ▪ The well-ordered, geometric shapes of salt and diamond crystals reflect the well-ordered geometric arrangement of their atoms.

 Amorphous solid: Atoms or molecules do not have long-range order.  Examples: glass, rubber, and plastic

 In liquid matter, atoms or molecules are close to each other but are free to move around and by each other.  Liquids have a fixed volume because their atoms or molecules are in close contact.  Liquids assume the shape of their containers because the atoms or molecules are free to move relative to one another.  Examples: Water, gasoline, alcohol, and mercury

 In gaseous matter, atoms or molecules are separated by large distances and are free to move relative to one another.  Since the atoms or molecules that compose gases are not in contact with one another, gases are compressible.  Gases always assume the shape and volume of their containers.  Examples: Oxygen, helium, and carbon dioxide

 Which image best represents matter in the gas state?

 Pure substance: composed of only one type of atom or molecule.  Mixture: composed of two or more different types of atoms or molecules combined in variable proportions.

 Pure substances include elements and compounds

 Element: A pure substance that cannot be broken down into simpler substances.  No chemical transformation can decompose an element into simpler substances.  All known elements are listed in the periodic table. ▪ Examples: hydrogen (H), carbon (C), iodine (I)

 Compound: A pure substance composed of two or more elements in fixed definite proportions.  Compounds are more common than pure elements.  Most elements are chemically reactive and combine with other elements to form compounds.  Compounds can be decomposed into simpler substances. ▪ Examples: water, table salt, sugar

Molecule/compound Molecule/element Atoms/element

 Pure substances can be represented with a chemical formula.  Examples?

 When matter contains two types of atoms, it may be a pure substance or a mixture.  A compound is a pure substance composed of different atoms that are chemically bonded in fixed definite proportions.  A mixture is composed of different substances that are not chemically bonded, but simply mixed together.

 Mixtures cannot be represented by a chemical formula.  Properties of mixtures can vary since proportions can vary.

 Homogeneous Mixture: a mixture of compounds or elements in which all regions are identical in composition and properties.

 Examples?

 Includes solutions, colloids, and alloys: ▪ Solutions: homogeneous mixtures in which all particles are dissolved. Solutions are usually transparent. ▪ Vinegar, Kool-aid, tea ▪ Colloids: homogeneous mixtures in which larger particles do not separate out from the mixture. Light is usually scattered when passing through. ▪ Milk, paint, smoke

▪ Alloys: a mixture of two metals, or a metal and a non-metal. ▪ Can also be heterogeneous! ▪ Examples: Brass = copper + zinc Steel = iron + carbon

 Heterogeneous Mixture: a mixture of compounds or elements in which separate regions are noticeable and have differing compositions and properties.

 Examples?

 Includes suspensions ▪ Suspension: mixture in which particles of one substance is dispersed in the other. These particles can be seen with the naked eye. Particles will settle out of the suspension if left undisturbed. ▪ Examples: sand in water, dust in the air

 In the diagram below, which pictures do you think represent mixtures and which represent pure substances? Explain your answers. (The spheres represent atoms.)

 Classify each type of matter as a pure substance or a mixture. If it is a pure substance, classify it as an element or a compound; if it is a mixture, classify it as homogeneous or heterogeneous.  (a) a lead weight  (b) seawater  (c) distilled water  (d) Italian salad dressing  (e) mercury in a thermometer  (f) exhaled air  (g) chicken noodle soup  (h) Sugar