Bellwork Chapter Pre-test: 1. What instrument would you use to measure temperature? Thermometer 2. Which of the following is a unit of volume? A. atmosphere B. gram C. meter D. liter D. 3. What characteristic of matter can you measure using a graduated cylinder? Volume 4. The sides of a cube are 2 cm by 2 cm. What is the volume of the cube? 8 cm3 5. What additional quantity would you need to calculate the density of the cube in question 4? Mass 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. D.

Physical science Chapter 2 Properties of Matter

Lab Groups of three-four will be made Each group will be provided 5 materials, a rubber band, a steel paper clip, a copper prong, wooden pencil or toothpick, and a graphite pencil filler. Determine the properties or characteristics of the materials by touching, smelling, and looking at them. Record these properties in a table/chart. After you record these properties, write a description of each material that could be used to clearly identify it.

Bellwork Finish the lab quickly so we can discuss your descriptions.

Possibilities Rubber’s elasticity Copper’s color Steel’s shininess Wood’s brittleness Graphite’s ability to leave a mark Description: Copper is a gold-ish solid that is flexible enough to be shaped and bent

Section objectives 1. Classify pure substances as elements or compounds. 2. Understand why are elements and compounds are classified as pure substances 3. Understand how mixtures differ from pure substances. 4. Know what the main difference is among solutions, suspensions, and colloids.

Heterogeneous mixture Matter Substance Element Compound Mixture Heterogeneous mixture Homogenous Mixture

Intro Your book uses the example of a care label on your clothes. Why is it there? A tendency to wrinkle is a property of cotton, the tendency to not wrinkle is a tendency of polyester, the tendency to shrink when washed is a property of wool. They all have different properties because they have different compositions. These compositions can be broken into pure substances and mixtures

Pure substances Matter that always has the same composition is classified as a pure substance, or substance Every sample of a given substance has the same properties because a substance has a fixed, uniform composition. Salt is a composition of sodium and chloride Substances can be classified into two categories, elements and compounds Matter Substance Elements Compounds

Elements There are only about 100 elements Element: a substance that cannot be broken down into simpler substances An atom is the smallest particle of an atom An element has a fixed composition because it contains only one type of atom.

Elements No two elements contain the same type of atom. Most elements are solids at room temperature (20 C, 68 F)

Examples Aluminum

Example Carbon

Elements Some elements are gas at room temperature Oxygen and nitrogen are the main gases we breathe

Bellwork Draw the diagram classifying the different types of matter What are elements made of? What form are most elements in at room temperature?

Liquid Elements Only two elements that are liquid at room temperature: Bromine and mercury, both are very poisonous

Symbols The symbols for elements are similar to why scientists use the SI system of measurement. Many symbols are based on the Latin name for the element and all scientists agree on the symbol for each element *project!: Choose an element you are unfamiliar with. Research the origin of the symbol. Then, research the application or use of the element. Write at least a paragraph detailing this information and turn it in on Thursday

Compounds Someone read the first paragraph under Compounds on pg. 40 A compound is a substance that is made from two or more simpler substances. The simpler substances are either elements or other compounds

Compounds continued THE PROPERTIES OF A COMPOUND DIFFER FROM THOSE OF THE SUBSTANCES FROM WHICH IT IS MADE Water is a compound made up of the elements hydrogen (H) and oxygen (O) Both of these elements are gases at room temperature, but water is a liquid Hydrogen can fuel a fire and oxygen is needed to keep it going, but water is used to put it out

COMPOUNDS COMPOUNDS ALWAYS CONTAIN TWO OR MORE ELEMENTS JOINED IN A FIXED PORTION Silicon dioxide, for example, is the compound found in most light colored sand It is made from the elements silicon ( a gray solid) and oxygen. It is always made with two oxygen atoms for each silicon atom. (di means 2) Same for water

Mixtures Mixtures tend to retain some of the properties of their individual substances But the properties of a mixture are less constant than the properties of a substance The properties of a mixture can vary because the composition of a mixture is not fixed.

On your own Read pages 41-44 Create a chart with descriptive visuals and examples to help you classify the different types of mixtures Heterogeneous Homogeneous Solutions Suspension Colloid When you finish, complete section 1 in your workbook

Types of mixtures Mixtures are combinations of substances The composition of the substances (unlike compounds) are not constant Example: salsa Heterogeneous mixtures: the parts that make up the mixture are noticeably different Example: sand

Bellwork Think of a homogeneous and a hetergeneous mixture

Heterogeneous Mixtures Hetero (different) genus (kind)

Homogeneous mixtures Homogeneous mixtures: the substances are so evenly distributed that it is difficult to distinguish one substance from another Example: a stainless steel spoon is a homogeneous mixture of iron, chromium and nickel

Homogeneous Mixtures

Solutions, Suspensions, Colloids Based on the size of its largest particles, a mixture can be classified as a solution, suspension, or a colloid

Solution Solution: when substances dissolve and form a homogeneous mixture Example: sugar dissolved in water Characteristics: Particles are too small to settle out of the solution Particles cannot be trapped by a filter Particles are too small to scatter light

Solution

Suspension “Shake Well” Suspension: a heterogeneous mixture that separates into layers over time Example: Sand and water Characteristics: Particles will settle Particles can be filtered Particles are large enough to scatter light

Suspension

Colloid Colloid: contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension. Example: homogeneous milk Characteristics: Particles do not separate into layers You cannot filter to separate parts of a colloid Particles are large enough to scatter light

Colloid

Mixture Solution Suspension Colloid Heterogeneous Homogeneous Combination of substances Solution When substances dissolve in a homogeneous mixture, sugar water Suspension Heterogeneous mixture that separates into layers, sand and water Colloid Homogeneous mixture with intermediate particles, milk, fog Heterogeneous Parts are noticeably different , sand Homogeneous Parts are evenly distributed, stainless steel spoon

Bellwork 8-29 Give an example of a solution, suspension, and a colloid

Examples of 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. Viscosity Conductivity Malleability Hardness Melting point Boiling point Density

Viscosity Viscosity: the tendency of a liquid to keep from flowing-its resistance to flowing The greater the viscosity the slower the liquid flows

Viscosity Viscosity usually decreases when heated Importance? Think motor oil…

Conductivity Conductivity: a material’s ability to allow heat to flow Materials with high conductivity (metals) are conductors If a material is a good conductor of heat it will usually do the same for electricity So why do we stir soup with a wooden spoon?

Conductive materials

Malleability Malleability: the ability of a solid to be hammered without shattering. Most metals are malleable Solids that shatter when struck are brittle Give an example of a malleable and brittle material.

Malleability

Hardness Hardness: how hard a material is To compare hardness you can try to scratch one object with another Diamond is the hardest material known

Hardness

Melting and boiling points Melting Point: The temperature at which a substance changes from a solid to liquid Boiling Point: The temperature at which a substance boils What are the melting and boiling points of water in Celsius? Are there any factors that can affect boiling point?

Melting/Boiling Points

Density Density: can be used to test the purity of a substance Examples include methanol for bike racing

Using Physical Properties to Identify Materials 1. Decide which properties to test 2. Perform tests on unknown samples 3. Compare data results with data reported for known materials Example: crime investigation

Recognizing Physical Change Physical Change: A physical change alters the form of a substance, but does not change it to another substance.

Using Properties to Choose Materials Properties determine which materials are chosen for which uses. Wood shoelaces?

Using Properties to Separate Mixtures Two properties are used to separate: Filtration Distillation Filtration: a process that separates materials based on the size and of their particles. What are some examples of filtration?

Homework Finish section 1 in your work/study book Finish your research on your symbol

Chemical Properties Chemical property: any ability to produce change in the composition of matter Chemical properties can only be observed when the substances in a sample of matter are changing into different substances. Example: Paraffin wax in a candle (made of compounds containing hydrogen and carbon). As the compounds burn they combine with oxygen and form water and carbon dioxide

Chemical Properties Flammability and Reactivity are two chemical properties of matter. Flammability: a material’s ability to burn in the presence of oxygen

Why does it matter? Think of some reasons why the flammability of a material or substance is important?

Reactivity Reactivity: how readily a substance combines with other substances Oxygen and iron are highly reactive substances. What happens when iron reacts with oxygen and water? What are some other materials that rust?

Rust

Reactivity Nitrogen has a low reactivity Because of this it is used to displace the reactivity of other substances Example: water tanks that stabilize ships are filled with seawater. The oxygen in the water reacts with the iron in the steel and creates rust Japanese engineers have pumped nitrogen in these tanks to displace the oxygen and decrease rust.

Recognizing chemical changes Chemical change occurs when a substance reacts and forms one or more new substances. Can you think of examples of chemical change?

Recognizing change Think of things that change chemically. What are some “side effects” of chemical change?

Recognizing Chemical Change 3 types of evidence for chemical change: 1. Change in Color 2. Production of gas 3. Formation of a precipitate

Change in Color A change in color is a clue that a chemical change has produced at least one new substance Copper + water+ Oxygen=Patina

Production of a Gas Can you think of an example of a production of gas when compounds or substances are combined?

Production of Gas Many gas reactions include carbon dioxide. When baking soda and vinegar are combined they form bubbles of carbon dioxide Baking soda in a cake combines with an acid and creates bubbles which make the cake rise

Formation of a Precipitate Any solid that forms and separates from a liquid mixture is called a precipitate What are some examples?

Formation of a Precipitate When acid is added to milk the proteins undergo a chemical change that alters their structure, causing them to stick together in clumps These clumps are cheese!

Chemical or Physical Change? Always ask, “are different substances present after the change takes place?” If not, then it is a physical change Chemical change= the composition of the matter changes Physical change=the composition of the matter remains the same. What are some examples of physical change that have evidence of chemical change?

Video for Chemical and Physical Change http://youtu.be/gCbqjs-pqJo