Chemistry The Science of Matter

Do Now List at least 5 chemicals that you are familiar with from past experience.

Learning Objective Understand composition and their impact on the properties of matter Be able to classify chemical vs. physical changes

Chemistry The science that investigates the structure and properties of matter – Matter: anything that takes up space and has mass Mass: the measure of the amount of matter that an object contains NOT Matter- – Heat – Light – Radio waves etc.

Matter continued Structure: refers to what it is made of and of how it is organized Properties: Describe the characteristics and behavior of matter including the changes it undergoes

Behavior of Matter Determined by BOTH – The elements it contains – Arrangement of those elements

Example Salt vs. Water Sodium and Chloride Hydrogen and Oxygen Contain different elements --- Have different properties!

Example AspirinVs Table Sugar Both contain only Carbon, Hydrogen and Oxygen molecules --- same composition Different Structures Cause Different Behaviors!

Example Two Different Artificial Sweeteners Aspartame Saccharine Different Compositions Both have: C, H, O and N and are sweet Only Saccharine has Na+ and S Their arrangement must be a factor!

Properties Many are easy to observe by simple tests Use heat, magnets, electricity etc – Color – State: solid, liquid or gas at room temp and pressure – Soft or hard – Does it burn? – Does it dissolve in water? These are from a macroscopic perspective – Things you can touch, taste, feel, smell and see

What is it made of? This question is harder to answer – Must take measurements – Must observe chemical changes Macroscopic Observations Submicroscopic perspective – To understand hidden structure influences behavior

Physical change vs. Chemical change Physical ChangeChemical Change Doesn't change what the substance is. A new substance is formed and energy is either given off or absorbed. Can be reversedCannot be reversed with the substance changed back without extraordinary means, if at all.

Examples Physical ChangeChemical Change Paper cut into pieces, small pieces are still paper Paper burned is no longer paper Dissolve sugar in waterMake a cake with flour, water, sugar and other ingredients and bake them, it would take extraordinary means to separate the various ingredients out to their original form.

Physical Vs. Chemical Change Worksheet (15 minutes) In pairs complete the given handout You may use your notes Students should each complete an answer sheet as a study guide Be sure that you are prepared to share your answers with the class

Share Answers

Chemical properties vs. Physical properties Chemical Property Flammability: The ability to burn Ability to rust: Reacts with oxygen to produce rust Reactivity with vinegar: Reacts with vinegar to produce new substances Physical Property Transparency: The property of letting light pass through something Boiling point: Temperature at which a substance goes from liquid to gas Melting point: Temperature at which a substance goes from solid to a liquid Brittleness: Tendency to crack or break Ductility: Ability to bend without breaking Elasticity: Ability to be stretched or compressed then return to original size Density: Mass per unit volume

Submicroscopic Level of Matter Matter is made of Atoms Atoms – So small they can not be seen with the most powerful light microscope – So small that if a period at the end of a sentence were made of Carbon atoms it would be made of 100 quintillion carbon atoms (100, 000,000,000,000,000,000) Counting them at 3 per second would take you a trillion years! – Scanning Tunneling Microscope (STM) creates computer images which are a visible perspective showing atomic location

Scanning Tunneling Microscope (STM) individual iron atoms on a silver substrate

Using Chemical Models Show types and numbers of atoms Show arrangement of the atoms and space filled

Why Models? Submicroscopic structural representation Explains observed behavior Used to predict behavior not yet observed Built on investigation and experimentation

Show Connections Between Atoms

Mixtures A material that is made of 2 or more things which are not combined chemically Each of the parts still keep their own identities Made by blending, but NOT forming chemical bonds or chemical change! Most everyday matter occurs as mixtures

Heterogeneous and Homogeneous Mixtures A classification of matter based on composition Homogeneous mixture: no clumping or grouping but rather a uniform dispersal of the material it is made of. – Ex. Air; made of N2, O2, CO2 and other gases – A liquid in which there is a solvent and a solute is called a solution Heterogeneous mixture: it is easy to identify all if the different components

Heterogeneous mixture

Colloids (look homogeneous but microscopically heterogenous) Hair spray Smoke Cloud Whipped cream Shaving cream Blood Styrofoam Gello

Dispersion (Heterogeneous) Dust Milk Hand cream Gravel Granite Sponge

Homogeneous Mixtures

Solutions (homogeneous) Air (gas) Martini (liquid) Salt water (liquid) Plastic (solid)

Substances Homogeneous materials that contain only 1 kind of matter Have definite composition and properties Substances which can not be broken down into a simpler substance is an ELEMENT. Substances which can be broken down into a simpler substance is a COMPOUND. – They are made of 2 or more elements

Elements Made of only one kind of atom Can not be made simplified by physical or chemical means Can exist as atoms (carbon) or molecules (N2)

Compounds Consist of 2 or more DIFFERENT atoms bound together (H2O) Can be broken down into smaller types of matter by chemical means only. Have properties which are different than the elements they are made of Always contain the same ratio of its components atoms ( ex 2 hydrogen's to 1 oxygen, in water)

Answers to pg 7 questions Ocean water- solution Calcium- element Vitamin C- Compound ( L-asorbic acid) Dry ice – compound (CO2) Copper- element Grain alcohol- compound (C2H5OH) after shave lotion- heterogenous mixture Hamburger- hetero Al foil – element Milk- solution Salt- cmpd Iron nail- element