Presentation on theme: "Chemistry The Science of Matter. Do Now List at least 5 chemicals that you are familiar with from past experience."— Presentation transcript:
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!
Identifying 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 (10 minutes) In pairs complete the given handout You may use your notes Be sure that you are prepared to share your answers with the class
Share Answers (3 min/group) Each table shares their answers with the class. Be sure to explain why you chose your answer. ALL STUDENTS MUST RECORD THE CORRECT ANSWER ON THEIR HANDOUT!
Exit Ticket – Answer individually Write your name! Please number your index card List 5 different properties of matter which can be used to identify a substance. 2.Define Chemical change 3.Define physical change 4.List 3 examples of a chemical change 5.List 3 examples of a physical change. PLACE YOUR EXIT TICKET IN THE TRAY ON YOUR WAY OUT! Thanks for doing your best work!
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
Let’s look closely at Density It is an important property of matter – It is used to identify substances – It is also used to separate mixtures Definition of Density: the mass of a specific unit of volume It is expressed in the following equation; D= m/v or density = mass volume
Density In solids it is usually expressed as; – grams per cubic meter g/cm 3 – Kilograms per cubic meter Kg/m 3 In liquids it is usually expressed as; – grams per liter g/L – grams per cubic centimeter g/cm 3
Example of Density Calculations If a piece of rock has a mass of 14g and a volume of 5 cm 3, what is the density? – Step 1: Write the given and ensure proper units m =14 g V= 5 cm 3 – Step 2: Write the formula D= m/v – Step 3: Substitute the given into the formula D = 14g / 5 cm 3 – Step 4: solve D=2.8 g/cm 3
Your turn to work! Alone, Silently Read the first 2 pages (4 min) – Highlight or underline any concepts which we have already mentioned as important, in ppt. – Circle any new information – Use a sticky note to write out any questions you have
Now you try some problems! Work with your partner to answer questions for practice exercise 1 and 3 (10 min) – You may use a calculator – Write out all steps – Label all units – Be prepared to put your answer on the board!
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
Classifying Matter 1.Substance: matter with constant composition a)Element: Made of only one type of atom b)Compound: 2 or more elements that are chemically combined 2.Mixture: Matter with variable composition a)Heterogeneous Mixture: Made up of more than 1 phase b)Homogeneous Mixture: also called solutions, made up of only 1 phase
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
Dispersion (Heterogeneous) Dust Milk Hand cream Gravel Granite Sponge
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)
Learning Objectives Investigate various ways to separate mixtures Identify the properties of the matter that allow for a particular method of separation
REMEMBER Mixtures Are 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
Separating Mixtures Mixtures can be separated through a physical process, (the identity of the substance remains unchanged). – Using their Physical properties – Bringing about physical changes to separate the mixture into its components (different substances it is made of)
REMEMBER: Physical Properties 1. Density: Mass per unit volume 2.Solubility in water : Does it dissolve in water? 3.State of mater: at room temp and pressure 4.Transparency: lets light pass through 5. Boiling point: Temperature at which a substance goes from liquid to gas 6.Melting point: Temperature at which a substance goes from solid to a liquid 7. Brittleness: Tendency to crack or break 8. Ductility: Ability to bend without breaking 9.Elasticity: Ability to be stretched or compressed then return to original size
Making a Mixture AND SANDSUGAR
How can we separate it? What do you think? – Work with your lab partner to come up with a suggested method. (10 minutes) – You may use your class notes, but your brain is your best asset. – Write your thoughts in your notebooks. – Do not be afraid to try!
Report out on ideas So, what did you come up with? Share your thoughts! (10 minutes)
What can we do? Method #1 Use a pair of tweezers and a microscope to physically separate the particles Requires a lot of time and patience
Method #2 Step #1 Recall the properties of water and of sand Sugar dissolves in water Sand does NOT Use the difference!
Step #2 Recall the properties again sand will not pass through a filter Sugar and water solution will Use the difference!
Step #3 Recall the properties of sugar and water sugar will not evaporate (change state) at 100 degrees Celsius water will ! Use the difference! Step #4
You have the two pure substances again! Sand in the filter! Sugar in the bottom of the beaker!
Learning objective Understand the relationship between chemical change and energy change
Mixtures vs. Pure substances Mixtures can be separated based physical properties and through physical change Pure substances can only be separated through chemical changes – Separated from compounds into elements H2O- H and O2 – Made into compounds from elements H + O H2O
Chemical Change and Energy All chemical changes involve some sort of energy change! Many chemical changes (reactions) release energy – Exothermic reactions: release energy as heat Some reactions absorb energy – Endothermic reactions: absorb heat energy
Demo Epsom salt and laundry detergent
Lab Thursday! Paper Chromatography! – A method of separating mixtures based on their ability to dissolve or on the size of particles.
More methods of separating mixtures Paper chromatography – Separating the dyes in ink Dyes are usually made of several basic colors called pigments Using the property of these dyes – Soluble in water we will separate the pigments
Develop a question! Make a claim (hypothesis) Follow the Procedure Answer the lab analysis questions Draw a conclusion Ask a new question Create a poster presentation of your results
Unit Test on Monday! Be sure to study your notes and your review sheets!