Chemistry and Changes 8th Grade Science .pdf
- 2. This week Monday- Observing chemical reactions Tuesday- What is chemistry Wednesday History of chemistry Thursday- Breakdown of atoms and molecules Friday- finishing up intro and short quiz
- 3. Observing chemical Reactions Today’s lab is an introduction where we will observe chemical reactions. We are doing this by building mini rockets and launching them outside with different chemicals. Remember lab procedure and safety this is a potentially dangerous lab
- 4. What is Chemistry The study of the composition of matter and the changes that happen to it ➔ Everything that is made up of matter is studied by some sort of chemist. ➔ Understanding chemistry will help you understand the world around you.
- 5. What kinds of careers involve chemistry? Pharmacist Doctor Chef Virologist Personal Trainer Geologist Paleontologist Farmer Forensics Dentist
- 6. Early Chemistry Jabir ibn Hayyan was an arabic chemist that lived from 751-815 AD. Attributed with the creation of distillation, crystallization, sublimation, and filtration.
- 7. History of Chemistry Chemistry started out as a way to make better things, soaps, dyes, glass and metalwork etc. ● This was not very “scientific” but did involve trial and error Modern chemistry began with Sir Robert Boyle ● He explained scientifically and mathematically the behavior of gases.
- 8. History (cont.) In the 1700s various scientists started to identify and name specific compounds and elements ● Some of the first were oxygen, chlorine, and nitrogen In 1807 Jon Dalton developed the atomic theory. Early 1800s - Amadeo Avogadro develops a systematic approach to measure the number of particles in a given amount of gas. ● Moles - 6.023 x 1023 ○ Number of particles in a chemical substance
- 9. Where do you see chemistry every day?
- 10. What is matter? ● Anything that has mass and takes up space. ● Made up of particles called atoms ● These atoms create everything in the universe
- 11. Atoms Protons - Found in the nucleus Neutrons - Found in the nucleus Electrons - Surrounding the nucleus 99% of an atom is empty space between the nucleus and the electrons
- 12. Protons # of protons in the nucleus tells you what element it is Each proton has a mass of 1au Positive charge 1.6605402E-24 g
- 13. Neutrons Each Neutron has a mass of 1au Neutral charge
- 14. Electrons Negative charge Move around the nucleus Negligible mass
- 17. Atoms like to have balance ● If a hydrogen atom has one proton (positive charge) it will prefer to have one electron (negative charge)
- 18. Valence Electrons Electrons surround the nucleus in balanced layers. ● The first layer will have a maximum of 2 electrons ● The next layers will have a maximum of 8 electrons The outermost layer is called the valence shell
- 19. PHET Simulation Get 4 or 5 stars on all 4 “Games” on the PHET science simulation and let me check it.
- 20. Build an Atom You need to Build an atom. Be sure to include: ● Correct number of Protons and Neutrons in the nucleus ● Correct number of electrons in the correct energy shells You also need to explain on your paper the chemical and physical properties of the element. Use your resources to find correct information. Information to include: ● Atomic Number & Symbol ● Atomic Mass ● Physical properties ● Chemical Properties ● Reactivity ● Any other interesting or important info- two facts in sentences
- 22. How Atoms Stick Together- Atomic Bonds
- 23. Elements - Each individual chemical substance that cannot be broken down into other substances. ● Oxygen (O), Hydrogen (H), Magnesium (Mg) etc. Compounds - A chemical substance that is made up of multiple elements bonded together. ● Water (H2 O), Carbon Dioxide (CO2 ), Glucose (C6 H12 O6 ) ● The number of each element is represented with subscript, if no subscript is given then there is one of that element
- 24. Are the following elements or compounds? Nitrogen Carbon Monoxide Helium Salt (Sodium Chloride) Sugar (Glucose) Methane N CO He NaCl C6 H12 O6 CH4
- 25. Why Do atoms Bond? ● To be as stable as possible. ● Complete Valence shell
- 26. Bonds Ionic- Atoms Transfer electrons Covalent- Atoms share electrons
- 27. Ionic Bonds ● Usually between a metal and a nonmetal ● Creates charged ions that attract each other ● Example: NaCl (table salt)
- 28. Covalent Bonds ● Usually between two nonmetals ● Atoms share electrons to fill shells ● Example: H₂O (water)
- 29. Chemical Compounds Some elements tend to bind together to be more stable: O2 = Oxygen Other compounds are created by multiple elements binding together to create a compound : H2 O = Water; C6 H12 O6 = Glucose
- 30. How do we write it? Subscript numbers after an element indicate how many atoms are present in a molecule Ex. O2 H2 0 C6 H12 O6
- 31. Properties What characteristics can we use to identify a chemical? Unit 8.1.2
- 32. Water is a chemical How would you describe water? What properties does it have? How might water change? How might it interact with other chemicals?
- 33. Characteristic Properties ● Properties that define an element ● Elements are pure substances made of only one type of atom. ● Every element has a unique set of properties that help identify it. ● Properties can be grouped into physical (can be observed without changing what the substance is) and chemical (describe how it reacts with other substances).
- 34. Chemical vs Physical “Guessing” Game Color Density Melting Point Flammability Ability to Rust Solubility Odor Reactivity With Oxygen Ability to Tarnish
- 36. Quiz Day- No bellwork
- 37. Physical Properties These can be observed or measured without changing the element into something new. Examples: ● State of Matter: solid, liquid, gas at room temperature ● Color: gold is yellow, copper is reddish-brown ● Density: mass per unit volume ● Melting Point / Boiling Point: temperature where it changes state ● Conductivity: how well it conducts electricity or heat ● Malleability: can be hammered into sheets ● Ductility: can be pulled into wires ● Luster: shiny or dull
- 38. Chemical Properties These describe how the element behaves in chemical reactions. Examples: ● Reactivity: how easily it reacts with other substances ○ Example: sodium reacts quickly with water, gold barely reacts at all ● Flammability: ability to burn ● Corrosion/Oxidation: tendency to rust or tarnish (iron rusts, silver tarnishes) ● Toxicity: harmful effects on living things ● pH behavior: acidic, basic, or neutral
- 39. How do we use these properties Identify an unknown element (match measured properties to known values) Classify elements in the periodic table (metals, nonmetals, metalloids) Predict how an element might behave in a reaction
- 40. ● Metals: shiny, good conductors, malleable, ductile, mostly solid at room temperature ● Nonmetals: dull, poor conductors, brittle, can be gases or solids ● Metalloids: share properties of both metals and nonmetals
- 41. Physical Change A change in the form or appearance of matter, without changing into a different substance. ● Change in shape ● Change in state of matter
- 42. Chemical Change A change in matter in which one or more new substances form ● Change in color ● Change in temperature ● Formation of a gas ● Formation of a precipitate ○ A solid substance that appears in a solution
- 43. Chemical Reaction Process by which substances interact to form new substances with different properties.
- 44. Chemical Reaction Equations Chemical Reaction - Process that occurs when one or more substances, called reactants, is changed into one or more substances, called products. Requires energy. Reactant Product Carbon + Oxygen Carbon Monoxide C + O CO
- 45. Reactant - The substance in a reaction that is changed. ➔ Left side of the equation. Product - The substance that is created in a reaction. ➔ Right side of the equation.
- 46. Law of Conservation of Mass In a system where reaction occurs, mass of the reactants cannot be removed or added in the products. In other words: Mass cannot be created or destroyed All elements present in the reactants will be present in the products. An equation is balanced when the reactants side of the equation has the same number of particles as the products side.
- 47. Law of conservation of energy