Syst è me Internationale SI Units

1. Système InternationaleSI Units

2. SI is a system of measurement used in science based on powers of 10. • Units are given using a prefix + a base unit Prefixes: Kilo- (K) 1,000 Hecto- (H) 100 Deka- (D) 10 Base unit- 1 deci- (d) 0.1 centi- (c) 0.01 milli- (m) 0.001 Base Units: Length = meter (m) Mass = gram (g) Volume = cubic meter (m³) or liters (L) Time = seconds (s) Temperature scale = celsius

3. To remember the prefixes… • King • Henry • Danced • By • Dirty • Cow • Manure

4. Conversion: 80cm= _________meters 80cm x 1m/100cm = 2000mm = ___________meters 2000mm x 1m/1000mm = 2 Kg = __________-mg 2Kg x 1,000,000mg/1Kg = 0.8 m 2 m 2,000,000 mg

5. 800mL = __________L 800mL x 1L/1,000mL = 7,500 cg = __________Kg 7,500 cg x 1Kg/100,000cg = 0.8 L 0.075 Kg K H D b d c m -You can also count how many times you are multiplying or dividing by 10 and then move the decimal point as necessary

6. SI Practice Conversions 1)2,345 g = ______________Kg 2)3,462 mL = _____________DL 3) 6.2 Km = ______________dm 4) 78 Hg = _______________Kg 5) 0.001 KL=_____________L 6) 0.000005 Km= _________mm 7) 520 cm = _____________m 8) 892.2 dm =____________Dm 9) 1,236,000mm³=_________Km³ 10) 3.5 hours= ___________seconds • 2.345 Kg • 0.3462 DL • 62,000dm • 7.8 Kg • 1L • 5mm • 5.2m • 8.922 Dm • 1.236 Km³ • 12,600 seconds

7. Elements, Compounds, and Mixtures We can describe matter based on its physical and chemical properties, but how do we organize it? Pure substances- any form of matter made of uniform particles Mixture- matter made of multiple types of particles that are not chemically bound

8. Pure substances are split into two categories… Elements- pure substance made up of only one type of atom -cannot be broken down into simpler substances by physical or chemical means Compounds- pure substance made up of multiple types of atoms, chemically bound to form particles called molecules

9. Elements are all made up of different types of atoms and organized according to their physical and chemical properties on the periodic table.

10. Compounds Compounds are made of chemically bound elements, but their properties can be different than the properties of the elements that make them. dangerous elements can make harmless compounds and vice versa A type of molecule is always made up of the same ratio of its component elements Examples- water is always 2 Hydrogen atoms and 1 oxygen -table salt is always 1 sodium atom and 1 chlorine atom

11. Compounds can be broken down during a chemical change. -Sometimes they need a catalyst, sometimes they need an input of energy, and sometimes they just degrade over time. Eat a steak, its proteins are broken down into amino acids (mechanical and chemical digestion) then your body reassembles the amino acids into other proteins (translation). Can you come up with any other examples of compound breaking down or being formed? Glucose Deoxyribonucleic acid

12. How do we know when a chemical change has taken place? Often the appearance (texture, color, physical state) can change. Other signs of change include… -heat -odor -fizzing and foaming -sound -light Unlike physical changes, chemical changes are hard to reverse -You can undo some reactions by chemical means, but most of the time it is difficult

13. Atoms: Theory and Structure- Review Atoms are the smallest unit of an element Each element is made-up of a different type of atom, distinguished by the number of the different subatomic particles that compose them. There are three subatomic particles that make-up an atom Proton: + charge and large mass (1amu) Neutron: 0 charge and large mass (1amu) Electron: - charge and small mass Protons and neutrons are found in the nucleus of the atom and electrons orbit around it, in what is called the electron cloud.

14. Atomic Theory: • All substances are made of atoms, which in turn are made of smaller particles called electrons, protons, and neutrons. • They can be divided or combined (difficultly)- nuclear fusion and fission • Atoms of the same element will all have the same number of protons and electrons, but the number of neutrons and as a result the mass may vary (isotopes). • Atoms do join with other atoms to form new substances (compounds)

15. Chemical Reactions Chemical reactions (chemical changes) occur when compounds form or degrade. This occurs as a result of chemical bonding, when electrons are shared, gained, or lost during the association of one atom with another Do all of an atom’s electrons take part in chemical bonding? No, usually only the valence electrons take part in chemical bonding

16. Valence electrons are the electrons on the outermost energy level -an atom can have between 1 and 8 of them -atoms bond with other atoms, gaining, losing, or sharing electrons, to get a complete set of 8.

17. Which groups of elements want to lose electrons? Which groups of elements want to gain electrons? Which groups will most likely share their electrons? There are different types of chemical bonds. The type depends on whether electrons are transferred or shared between atoms.

18. Ionic Bonding A type of bonding in which electrons are transferred from one atom to another Atoms are usually neutrally charged, having an equal number of + protons and –electrons, but during an ionic bond that number is no longer equal. In one of the bonding atoms, the number of electrons is greater than the number of protons. -they are negatively charged In the other bonding atom, the number of electrons is less than the number of protons. -they are positively charged

19. Charged atoms are called ions -positively charged ions are called cations -negatively charged ions are called anions Does an ionic compound, made of one cation and one anion, have a charge? No, the atoms in the compound are now charged, but the compound itself is neutral

20. Ionic compounds bond together in rigid, geometric structures or chrystals. -the actual shape in which they form is called a chrystal lattice

21. Identify the cation and anion in each of these ionic compounds CaCl2 Ba K2S FeBr3 Cr2O3 KI NaCl FeO KF FrBr

22. Usually when an atom has more than one or two electrons to gain or lose it cannot transfer its electrons. In these cases they will share electrons, forming covalent bonds Compounds formed of covalent bonds are called molecules -a molecule is the simplest form of a covalent pure substance Organic compounds (anything containing carbon) are all covalent. -glucose -starch -celullose

23. You can diagram a molecule using an electron-dot diagram or Lewis structure. • Drawing an electron-dot diagram… • Write the element symbol of the largest atom • Draw dots around it representing its number of valence electrons • Try to space them evenly in groups of two • Place the other atoms around it in a way that allows each atom to have 8 valence electrons (2 for hydrogen).

24. -A pair of electrons involved in a bond can be represented using a bar. (single bond) -4 electrons involved in a double bond can be represented using a double bar (double bond) -6 by a triple bar (triple bond)

25. Other types of Chemical Bonding There are two other types of chemical bonding, metallic and hydrogen bonding They do not result in new compounds like ionic and covalent bonding. Instead they associate or hold like atoms together. Metals are usually very dense, meaning that their atoms are very close together. As a result their electron clouds overlap and their valence electrons are allowed to move throughout the substance. Hydrogen, because it is so simple an atom, when it binds with electronegative atoms (want to take electrons) becomes slightly positive. It will then associate with electronegative atoms of other molecules, limiting how far apart the different molecules can go without more energy.

26. Metallic bonding gives metals some unique properties, such as electrical conductivity, ductility, and malleability. Electrical conductivity- since the valence electrons can move freely through metals, an electric current (moving electrons) can also. Ductility- ability to be drawn into wire Malleability- ability to be hammered into sheets Basically, metal can be bent into any shape necessary and can be used to direct electricity.

27. As a result of hydrogen bonding, water molecules tend to stick together. This gives water molecules several unique properties…adhesion, cohesion, and surface tension Adhesion- water molecule’s tendency to stick to other objects Cohesion- water molecule’s tendency to stick to each other Surface tension- water molecule’s tendency to form a rigid surface at the top of a liquid These properties explain capillary action

28. Signs of Chemical Reactions Chemical reactions often give us physical evidence that a reaction is taking place. Such as… Color change Precipitate formation (forming a solid) Gas release (creating a gas) Heat (energy release)

31. Compounds are represented using chemical formulas (e.g. H2O) and chemical reactions are represented using chemical equations. 6 CO2 + 6H2O C6H12O6 + 6O2 Chemical equations tell you the chemical formulas of all of the compounds involved and how many of each compound is involved. We know… -the number of each compound -The kinds of atoms involved -the number of each kind of atom The compounds entering the reaction are called reactants The compounds produced in the reaction are called products

32. The one BIG rule The atoms in the reactants much equal the atoms in the products The Law of Conservation of Mass -Mass (matter) is neither created nor destroyed during a normal chemical or physical reaction As a result the atoms present before a reaction must also be present after a reaction

33. To balance equations and make sure that no matter is lost or created, we use coefficients. -they tell us how many of a particular compound is involved in a reaction -By adding them to one, two, or all of the compounds involved in a reaction we can be sure that the same number of atoms enter and leave a reaction. CO2 + H2O C6H12O6 + O2 6CO2 + 6H2O C6H12O6 + 6O2 Balancing chemical equations is part of a branch of chemistry called Stoichiometry

34. Energy Energy is the ability/potential to do work (move matter). When matter interacts energy is transferred back and forth. Something with a lot of energy could do a lot of work Or To do a lot of work (moving something massive), it requires a lot of energy

35. Energy in Chemical Reactions Iron reacts with oxygen to form rust. How come your car doesn’t spontaneously rust and fall apart? Plants bond carbon dioxide and water to make glucose, why can they not do this without light? How come, after you remove the initial flame from a candle, it continues to burn? The answer is energy energy is transferred, released, or absorbed whenever chemical bonds form or break This causes some reactions to take place very slowly, some to take place very quickly, some to require a constant or initial input of energy, and some to release energy to the environment.

36. Energy is absorbed when chemical bonds break and released when they form. If a chemical reaction absorbs more energy breaking up its reactants than its products release while being put together, then the reaction is called endothermic. -Endothermic- heat enters -Endo- inside Photosynthesis is an endothermic reaction -the absorbed energy comes from the sun

37. If a chemical reactions releases more energy bonding its products than it absorbs breaking its reactants, then the reaction is called exothermic. -Exothermic- heat exits -Exo- outside-exit Cellular respiration is an exothermic reaction -the energy released from breaking up glucose fuels our bodies

38. Some reactions will occur spontaneously without any initial input of energy, but most of the time, even exothermic reactions need an initial input of energy to get them started. The amount of energy a reaction needs to get started is called activation energy Exothermic reaction- heat energy given off by products Endothermic reaction- heat energy stored by products

39. The speed at which reactants break and products form during a chemical reaction is called its reaction rate. Reaction rate is affected by how exposed the reactants are to each other and the amount of ambient energy to start the reaction. To speed up a reaction… Increasing the temperature increases the amount of energy Increasing the concentration of the reactants, the surface area on which the can react, adding a catalyst, or removing an inhibitor increases how exposed the reactants are to each other. Catalyst- anything that lowers the activation energy required to start and maintain a reaction Inhibitor-anything that increases the activation energy required to start or maintain a reaction. -neither catalysts nor inhibitors are chemically changed during a reaction

40. Color Quiz • Does a catalyst increase or decrease reaction rate? • Black- increase orange-decrease 2) What is activation energy? Black- energy needed to start a reaction Orange- energy gained during a reaction 3) During an exothermic reaction, is the net energy gain positive or negative? Black- positive Orange- negative 4) During an exothermic reaction, the products … Black- absorb heat Orange- release heat 5) During an endothermic reaction, is more heat absorbed or released? Black- released Orange-absorbed 6) Photosynthesis is an example of what type of reaction? Black-endothermic Orange-exothermic

41. Energy associated with the motion and position of objects is called mechanical energy. It is split into two types, kinetic energy and potential energy. Kinetic energy is the energy of motion, describing how an object moves. Potential energy is the energy of position, describing the potential an object has to move as a result of its position in the universe. Mechanical energy = Kinetic energy + Potential Energy

42. Kinetic energy depends on the mass of an object and how fast it is moving (its velocity). EK = (1/2)mv2 E = energy K= type of energy M= mass V= velocity Which value affects an objects kinetic energy more, mass or velocity? (p.241 practice)

43. Potential Energy comes in two forms, elastic potential and gravitational potential. Elastic potential energy is an objects potential to spring back after being stressed somehow. e.g- stretching rubber band, drawing back a bow, compressing a spring Gravitational potential energy is an objects potential to move as a result of gravity (to fall). It depends on the height of an object and its weight (mass and force of gravity) Eg = mgh E= energy G=type of energy M= mass G= acceleration of gravity (9.8m/s²) H= height P.242 practice It can also be given as… Gravitational potential energy = weight x height

44. When an object falls or an elastic is released, its potential energy is converted into kinetic energy, but the total amount of energy stays the same. When the ball hits the ground and stops moving, its mechanical energy is gone. Where did it go?

45. Energy that appears to be lost is really just transferred into a new form. There are seven forms of energy… • Mechanical energy-energy associated with motion and position • 2) Thermal energy- energy associated with heat (vibration of particles) • 3) Chemical energy- energy stored in chemical bonds • 4) Electrical energy- energy associated with moving electrons • 5) Sound energy- energy of vibrating objects moving in waves through matter • 6) Light/radiant energy- energy moving through electromagnetic waves, can travel outside matter • 7) Nuclear energy- energy stored in the nucleus of an atom and released during fission and fusion We will talk in detail about heat, light, and sound later

46. Energy is converted from one form to another constantly and is involved in nearly every event or occurrence in the universe Example: Mechanical energy of water (kinetic), transfers to a turbine that converts mechanical energy into electric energy. A light bulb then converts that electrical energy into radiant and thermal energy that is transferred to the particles in the room around the light. Your eye receives the radiant energy and converts it back into electric energy that travels through your optic nerve and to your brain. The purpose of a lot of the machines that humans use is to convert energy from one form to another. -the engine in a car converts chemical energy in gasoline into thermal and kinetic energy.

47. Hydrotubine Wind turbine

48. The Law of Conservation of Energy says that energy cannot be created or destroyed -There is more energy in your food than you can use as fuel to move. -There is more energy gasoline than your car can use to move. No machine or natural energy conversion is 100% effective, though, so where does the energy go? Whenever an object moves, there is a force that pushes in the opposite direction that resists its motion. This force is called friction. The energy wasted to overcome friction is converted into thermal energy. Thermal energy, waste energy, is released in every energy conversion.

49. How efficient a machine or process is depends on how much energy is wasted overcoming friction. The less thermal energy released during an energy conversion, the more efficient it is. The more energy efficient a process is, the less fuel it needs in the first place.

50. Energy Resources Our energy resources on earth are split into two groups, renewable and nonrenewable. Renewable resources can be regenerated or provide an unlimited supply of energy. e.g. biomass (regenerated), wind, solar (unlimited supply) Nonrenewable resources cannot be regenerated under reasonable means. There is a finite supply of them on earth. e.g. fossil fuels, uranium -basically anything that comes from mining