Chemistry Chapter 2: Properties of Matter

Pre-Test 1. What instrument would you use to measure temperature? 2. Which of the following is a unit of volume? A. Gram B. Atmosphere C. Meter D. Liter

Pre-test Continued… 3. What characteristic of matter can you measure using a graduated cylinder? 4. The sides of a cube are 2 cm by 2cm. What is the volume of the cube? 5.What additional quantity would you need to calculate the density of the cube described in #4?

Pre-test Continued… 6. Which of the following topics is not studied in chemistry? A. Composition of matter B. Reactions of substances C. Properties of materials D. Motion of large objects

2.1- Classifying Matter Matter- anything that has mass and volume Two main types of matter Pure Substances Mixtures

Pure Substance Matter that always has exactly the same composition is classified as a pure substance Every sample of a given substance has the same properties because a substance has a fixed, uniform composition

Pure Substance Element: a substance that cannot be broken down into simpler substances All elements can be found on the periodic table An element has a fixed composition because it contains only one type of atom Element: Symbols-first letter capitalized, if there is a second letter, it is lowercase Developed so scientists around the world can communicate and share results Symbols come from latin or greek names for the elements

Pure Substance Compounds: A substance that is made from two or more simpler substances and can be broken down into simpler substances by chemical means Properties of a compound are different than the properties of the substances that make it up Compounds: A compound always contains two or more elements joined in a fixed proportion

Examples Elements: Carbon-C Oxygen-O Copper-Cu Compounds: CO-Carbon Monoxide NaCl-table salt- sodium chloride H 2 O-Water- dihydrogen oxide

Mixtures The properties of a mixture can vary because the composition of a mixture is not fixed Mixtures tend to retain some of the properties of their individual substances

Mixture Heterogeneous: Word parts: hetero- means different genus- means kind The parts of a heterogeneous mixture are noticeably different from one another Non-uniform composition If you took two different samples of this type of mixture they would not have the same composition Heterogeneous: Suspension: A heterogeneous mixture that separates into layers over time You could use a filter to separate the substances When light shines through a suspension, it is scattered (translucent or opaque )

Mixture Heterogeneous : Examples : Sand Granite Italian dressing Oil and water

Mixture Homogeneous: The substances are so evenly distributed that it is difficult to distinguish one substance from another Appears to contain only one substance Homogeneous: Solution: when substances dissolve and form a mixture Two parts in a homogeneous mixture Solvent-what does the dissolving Solute-what gets dissolved Do not separate into layers, cannot be filtered, light passes through a liquid solution without being scattered Particles in a sol’n are too small to settle, be trapped, or scatter light

Mixtures Colloids Contains some particles that are intermediate in size between the small particles in a sol’n and the larger particles in a suspension Do not separate into layers Cannot use a filter to separate the parts When light passes through a colloid it is scattered Mixtures can be categorized as a sol’n, colloid, or suspension by the size of their largest particles

2.2-Physical Properties Physical Property- any characteristic of a material that can be observed or measured without changing the composition of the substances in the material Examples: Viscosity Conductivity Malleablility Hardness Melting point Boiling point density

Descriptions of Physical Properties Viscosity The resistance of a liquid to flow The tendency of a liquid to keep from flowing The higher the viscosity of a liquid, the slower it will flow Does temperature affect viscosity? weblogs.baltimoresun.com/ features/green/2009/06 greentopher.blogspot.com/ 2008/01/honey.html YES!

Descriptions of Physical Properties Conductivity A material’s ability to allow heat to flow Materials with a high conductivity are called conductors ex: metals Materials with a low conductivity are called insulators ex: wood

Descriptions of Physical Properties Malleability The ability of a solid to be hammered without shattering Most metals are malleable Brittle Solids that shatter when hit Glass, ice

Descriptions of Physical Properties Hardness Mohs Scale Remember??? 1-10, 1 being the softest (talc) and 10 being the hardest (diamonds) One way to compare the hardness of two materials is to see which of the materials can scratch the other Melting and Boiling Points Melting point-the temperature at which a substance changes from solid to liquid Boiling point-the temperature at which a substance boils

Descriptions of Physical Properties Density Can be used to test the purity of a substance Ratio of the mass of a substance to the volume of a substance D = M/V

Using Physical Properties Physical Properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture

Using Physical Properties… …to identify materials 1st: decide what properties to test 2nd: test a sample of the unknown 3rd: compare results with known data …to choose materials ex: you wouldn’t want to use a stick of wax to stir your spaghetti sauce Why?

Using Physical Properties to Separate Mixtures Filtration A process that separates materials based on the size of their particles Distillation This process is often used if filtration cannot be used A process that separates the substances in a solution based on their boiling points Filtration and Distillation are two common methods

Physical Changes Physical Change- occurs when some of the properties of a material change, but the substances in the material remain the same Some physical changes can be reversed, some cannot

2.3 Chemical Properties Chemical Property- any ability to produce a change in the composition of matter Observing Chemical Properties Chemical Properties can be observed only when the substances in a sample of matter are changing into different substances

Chemical Properties Flammability A material’s ability to burn in the presence of oxygen home-and-garden.webshots.com/photo/ JxVHds

Chemical Properties Reactivity The tendency of a substance to to combine chemically with other substances nuclearnrg-psa.blogspot.com/2009_02_01_archive.html

Recognizing Chemical Changes Chemical Change- occurs when a substance reacts and forms one or more new substances (the original substance is no longer present) When a chemical change takes place new substance(s) are formed and there is evidence that a change occurred

Recognizing Chemical Changes Common types of evidence for a chemical change follow: Change in color Production of a gas Formation of a precipitate Energy (heat/light) given off Energy used (it will get very cold) Odor given off

Recognizing Chemical Changes Change in Color Copper turns greenish Match head turns black/gray

Recognizing Chemical Changes Production of a Gas Vinegar and baking soda (CO 2 given off) Electrolysis of water H 2 and O 2 gas given off Bread rising due to the formation of CO 2 when yeast causes fermentation to take place Formation of a Precipitate Precipitate- any solid that forms and separates from a liquid mixture genchem.chem.wisc.edu/sstutorial/Text8/Tx82/tx82.html

Chemical or Physical Change? When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same. Before you decide whether or not a chemical change has taken place ask yourself: Are different substances present after the change takes place?