Presentation on theme: "Making and breaking bonds….. Remember Democritus?...he is the “scary” looking greek from 2,000 years ago who believed in –ATOMS! –But he also thought."— Presentation transcript:
Making and breaking bonds….
Remember Democritus?...he is the “scary” looking greek from 2,000 years ago who believed in –ATOMS! –But he also thought atoms were the smallest particle out there Scientists came back to Democritus’ idea and added to it.
Imagine you could take apart all the particles in this grain of salt. Next you arrange all the particles in a row. Would it be long enough to make a necklace? How long would the row of particle be?
All that from just one grain of salt! What does tell us about the number and size of the particles? That’s more than 33 times the distance from the Earth to the Moon! metres Democritus never found out the answer to his salty puzzle. Thousands of years later, we know just how long the row of salt particles would be…
The number of particles is very, very, very, very, very, very, very, very, very, very,very, very big! The size of the particles must be very, very, very, very, very, very, very, very, very, very, very small! So next time you pour salt on your chips spare a thought for all those tiny salt particles!
Particles make up all matter and have mass Particles have different shapes and sizes Particles show ‘stickiness’, or the ability to bond with each other due to electrostatic attraction Particles can have ‘poles’ of greater or lesser charge Particles have energy which translates into motion
The particle model of a solid
The particle model of a liquid
The particle model of a gas
Solid particles... - are very close together in a fixed arrangement - have a small amount of energy - vibrate but do not move liquid particles… - are close together but have no fixed arrangement - more energy than solid particles - vibrate and can move about gas particles - are far apart and have no fixed arrangement - have a large amount of energy - move rapidly in all directions
Its state depends on how much energy the water particles have. If enough energy is added to or removed from the particles a change of state can occur. ice water steam
Draw a picture to show what is happening to the food coloring particles after they are dropped into a beaker of water…
Scientists find the particle model useful for two reasons. First, it provides a reasonable explanation for the behavior of matter. Second, it presents a very important idea—the particles of matter are always moving. Matter that seems perfectly motionless is not motionless at all. The air you breathe, your books, your desk, and even your body all consist of particles that are in constant motion. Thus, the particle model can be used to explain the properties of solids, liquids, and gases. It can also be used to explain what happens
Over the next 5 minutes, find a few objects and try to break them apart. Rules: –Objects cannot be mine –will not hurt anyone or anyone else’s property
Breaking bonds requires ENERGY So, just using logic, making bonds must releases energy Pick one object and remember that breaking process as your ANCHOR
Bonds: break old (use energy), recombine to form new bonds (release energy). 2 H-H bonds are broken, 2 O=O, costing energy, and 4 H-O bonds are made and energy is released. Energies to make and break these bonds are known. Using the bond energies of H-H 104 kcal/mole, O-O 119 kcal/mole, and H-O 111kcal/mole from Table 8, we can see how much energy is released when bonds are broken and formed.
The energy needed to break the bonds apart is called the “activation energy”. It is the bump in the graph. AE is the amount of kinetic energy required by the moving H 2 and O 2 molecules to rip them apart and slam into each other to create H 2 O.
When it looks like a reaction is done, it is only in equilibrium…some reactants making product AND some products are turning back into reactants.. 2H 2(g) + O 2(g) 2H 2 O(l)
How fast a reaction proceeds and which direction it favors (forward or reverse) depends on several factors: –Amount of reactants and products More reactants will push forward More product will push reverse –Temperature Higher temp causes more movement of atoms Direction of push depends if exothermic or endothermic –Pressure Works like increasing amount of gases on either side –Presence of a catalyst Lowers activation energy 2H 2(g) + O 2(g) 2H 2 O(l)
Write one paragraph (four or more sentences) explaining an example or a metaphor for equilibrium. Specify the forward reaction and the backward reaction. Describe one thing you could do to change the system and what the effect would be. AND Sec 18.1 #1-5 p547