Category: My Classroom Material

Orbitals

What is an Atomic Orbital?

Orbitals and Orbits 

When the a planet moves around the sun, you can plot a definite path for it which is called an orbit. A simple view of the atom looks similar and you may have pictured the electrons as orbiting around the nucleus. The truth is different, and electrons in fact inhabit regions of space known as orbitals. If an electron is in a particular orbital it will have a particular definable energy.

Each orbital has a name.

The orbital occupied by the hydrogen electron is called a 1s orbital. The “1” represents the fact that the orbital is in the energy level closest to the nucleus. The “s” tells you about the shape of the orbital. s orbitals are spherically symmetric around the nucleus – in each case, like a hollow ball made of rather chunky material with the nucleus at its centre.

Hydrogen’s electron – the 1s orbital   

 

 

 

The orbital on the left is a 2s orbital. This is similar to a 1s orbital except that the region where there is the greatest chance of finding the electron is further from the nucleus – this is an orbital at the second energy level.

 

 

2s (and 3s, 4s, etc) electrons spend some of their time closer to the nucleus than you might expect. The effect of this is to slightly reduce the energy of electrons in s orbitals. The nearer the nucleus the electrons get, the lower their energy.

3s, 4s (etc) orbitals get progressively further from the nucleus.

p orbitals

Not all electrons inhabit s orbitals (in fact, very few electrons live in s orbitals). At the first energy level, the only orbital available to electrons is the 1s orbital, but at the second level, as well as a 2s orbital, there are also orbitals called 2p orbitals.

A p orbital is rather like 2 identical balloons tied together at the nucleus. The diagram on the right is a cross-section through that 3-dimensional region of space. Once again, the orbital shows where there is a 95% chance of finding a particular electron.

Unlike an s orbital, a p orbital points in a particular direction – the one drawn points up and down the page. At any one energy level it is possible to have three absolutely equivalent p orbitals pointing mutually at right angles to each other. These are arbitrarily given the symbols px, py and pz. The p orbitals at the second energy level are called 2px, 2py and 2pz. All levels except for the first level have p orbitals.

d and f orbitals

In addition to s and p orbitals, there are two other sets of orbitals which become available for electrons to inhabit at higher energy levels. At the third level, there is a set of five d orbitals (with complicated shapes and names) as well as the 3s and 3p orbitals (3px, 3py, 3pz). At the third level there are a total of nine orbitals altogether.

Fitting electrons into orbitals

You can think of an atom as a very bizarre house (like an inverted pyramid!) – with the nucleus living on the ground floor, and then various rooms (orbitals) on the higher floors occupied by the electrons. On the first floor there is only 1 room (the 1s orbital); on the second floor there are 4 rooms (the 2s, 2px, 2py and 2pz orbitals); on the third floor there are 9 rooms (one 3s orbital, three 3p orbitals and five 3d orbitals); and so on. But the rooms aren’t very big . . . Each orbital can only hold 2 electrons.

A convenient way of showing the orbitals that the electrons live in is to draw “electrons-in-boxes”.

“Electrons-in-boxes”

Orbitals can be represented as boxes with the electrons in them shown as arrows. Often an up-arrow and a down-arrow are used to show that the electrons are in some way different. The diagram (not to scale) summarizes the energies of the orbitals up to the 4p level. Notice that the s orbital always has a slightly lower energy than the p orbitals at the same energy level, so the s orbital always fills with electrons before the corresponding p orbitals.

 

The order of filling orbitals

Electrons fill low energy orbitals (closer to the nucleus) before they fill higher energy ones. Where there is a choice between orbitals of equal energy, they fill the orbitals singly as far as possible.

 

Origin of life PPT Qs

Origin Of Life
ppt Questions

Early Thoughts on Life

1. What was Aristotle’s idea about how life arose called?

2. What is another name for spontaneous generation?

3. Explain spontaneous generation of life.

 

4. How long did the idea of abiogenesis or spontaneous generation last?

5. The idea of abiogenesis lasted so long because, instead of testing their ideas, people based their beliefs on what?

 

6. Were their observations tested?

7. Did they use the scientific method for their observations?

Examples of Spontaneous Generation

8. What observation about new life did Egyptians make when the Nile River flooded each year?

 

9. What observation about new life did Medieval farmers make when they stored their grain each year?

 

10. The English people centuries ago, threw their garbage and sewage out on the streets. What observation about new life did these people make?

 

 

11. This practice led to a plague that killed many Europeans. What was this plague called and what carried the disease organism?

 

 

 

12.Before refrigerators, large slabs of meat were hung after being purchased. What observation about new life was made from this practice?

 

 

13. People believed so strongly in abiogenesis that they had recipes for making living things. Name two organisms that had accepted recipes.

 

Disproving Spontaneous Generation

14. Francesco ____________ was an early scientists who conducted experiments to try and disprove spontaneous generation.

15. What was Redi’s hypothesis?

 

16. Explain how Redi tried to prove this.

 

 

 

17. What were the results Redi found in the closed jars & why?

 

18. What were the results in the open jars?

 

19. How did maggots appear in the open jars?

 

20. Complete this table summarizing Redi’s experiment:

 

Evidence Against Spontaneous Generation
Unsealed Jar
Sealed Jar
Gauze Covered jar

 

21. Redi’s experiment disproved spontaneous generation for _____________ organisms.

Use of the Scientific Method

22. Did Francesco Redi use the scientific method in his experiment?

23. What served as the control in Redi’s experiment?

 

24. What jars served as the experimental groups?

25. What was Redi’s conclusion?

 

Disproving Spontaneous Generation of Microbes

26. Anton Van _______________ made one of the first simple microscopes.

27. Leeuwenhoek called the living things he saw in pond water ______________.

28. By the end of the 19th century, these organisms were known as ______________.

29. John _____________ did experiments with microorganisms growing in broths.

30. Needham believed there was a __________ __________ present in nonliving substances like air.

31. Why were bacteria able to grow in Needham’s soups?

 

32. What could have been done to the broths to kill the bacteria already present?

33. What scientists repeated this experiment but with boiled broth?

34. After boiling, what did Spallanzani do to the tops of the bottles? how did this help?

 

35. Critics of Spallanzani’s experiment said there was not enough _______ for the bacteria to survive and that boiling had destroyed the _________ __________.

The Theory Changes

36. What did the Paris Academy of Science do in 1860 to solve the problem?

 

37.Who won the prize? 

38. What was Pasteur’s experimental hypothesis?

 

39. What was the shape of Pasteur’s flasks? Include a sketch.

 

 

40. What was the special S-shaped neck intended to do?

 

41. Did Pasteur boil the broth in his flasks? Why?

 

42. The flasks were left at ___________ locations.

43. Did the broth change cloudy because microbes were growing in it?

 

44. What was visible in the neck of the flask after collecting there?

45. Once the S-shaped stem was broken off the top of the flasks, what happened to the broth and why?

 

46. Pasteur’s S-shaped flasks kept ___________ out but let ______ inside.

47. Pasteur’s experiment proved that living things only come from other _________ ___________.

48. What is the name of Pasteur’s theory?

Review

49. Where did the maggots come from in Redi’s experiment?

50. What was the purpose of the sealed jars?

51. Redi was trying to disprove – spontaneous generation or biogenesis?

52. Where did the microbes come from in Needham’s broth?

53. Needham & Spallanzani were trying to disprove – spontaneous generation or biogenesis?

54.Who proved biogenesis?

 

 

 

Osmosis & Diffusion in Egg Lab

 

Osmosis & Diffusion in an Egg

 

Objective:
In this investigation, you will use a fresh hen’s egg to determine what happens during osmosis & diffusion across membranes.

Materials: (per lab group)
1-2 fresh hen eggs in their shells, masking tape & marker, distilled water, clear sugar syrup (Karo, for example), vinegar, clear jar with lid, tongs, electronic balance, paper towels, paper, pencil

Procedure:

Day 1   

  1. Label the jar with your lab group & the word “vinegar”.
  2. Mass the egg with the electronic balance & record in the data table.
  3. Carefully place the raw egg into the jar & cover the egg with vinegar.
  4. Loosely re-cap the jar & allow the jar to sit for 24 to 48 hours until the outer calcium shell is removed.

Day 2   

  1. Open the jar & pour off the vinegar.
  2. Use tongs to carefully remove the egg to a paper towel & pat it dry.
  3. Record the size & appearance of your egg in your data table.
  4. Mass the egg on an electronic balance & record.
  5. Clean and re-label the jar with your lab group & the word “distilled water”.
  6. Carefully place the egg into the jar & cover the egg with distilled water.
  7. Loosely re-cap the jar & allow it to sit for 24 hours.

Day 3   

  1. Open the jar & discard the distilled water.
  2. Use tongs to carefully remove the egg to a paper towel & pat it dry.
  3. Record the size & appearance of your egg in your data table.
  4. Mass the egg on an electronic balance & record.
  5. Clean and re-label the jar with your lab group & the word “syrup”.
  6. Carefully place the egg into the jar & cover the egg with clear syrup.
  7. Loosely re-cap the jar & allow it to sit for 24 hours.

Day 4   

  1. Open the jar & pour off the syrup.
  2. Use tongs to very carefully remove the egg & rinse off the excess syrup under slow running water.
  3. Pat the egg dry on a paper towel.
  4. Record the size & appearance of your egg in your data table.
  5. Mass the egg on an electronic balance & record.
  6. Clean up your work area & put away all lab equipment.

Data:

 

RESULTS OF DIFFUSION
Original Mass Final Mass Appearance of Egg
VINEGAR
WATER
SYRUP

 

 

Questions & Conclusion:

1. Vinegar is made of acetic acid & water. Explain how it was able to remove the calcium shell.

 

2. (a) What happened to the size of the egg after remaining in vinegar?

(b) Was there more or less liquid left in the jar?

   (c) Did water move into or out of the egg? Why?

 

3. (a) What happened to the size of the egg after remaining in distilled water?

(b) Was there more or less liquid left in the jar?

   (c) Did water move into or out of the egg? Why?

 

4. (a) What happened to the size of the egg after remaining in syrup?

(b) Was there more or less liquid left in the jar?

   (c) Did water move into or out of the egg? Why?

 

5. Was the egg larger after remaining in water or vinegar? Why?

 

6. Why are fresh vegetables sprinkled with water at markets?

 

7. Roads are sometimes salted to melt ice. What does this salting do to the plants along roadsides & why?

 

 

 

 

Mollusk

Mollusks


All Materials © Cmassengale  

Phylum Mollusca
Characteristics

  • Soft-bodied invertebrate covered with protective mantle that may or may not form a hard, calcium carbonate shell
  • Includes chitons, snails, slugs, clams, oysters, squid, octopus, & nautilus
  • Second largest animal phylum
  • Have a muscular foot for movement which is modified into tentacles for squid & octopus
  • Complete, one-way digestive tract with a mouth & anus
  • Have a fully-lined coelom
  • Cephalization – have a distinct head with sense organs & brain
  • Have a scraping, mouth-like structure called the radula
  • Go through free-swimming larval stage called trochophore


Trochophore Larva

  • Body organs called visceral mass lie below mantle
  • Have circulatory, respiratory, digestive, excretory, nervous, & reproductive systems
  • Bilaterally symmetrical
  • Most have separate sexes that cross-fertilize eggs
  • Gills between the mantle & visceral mass are used for gas exchange
  • Includes 4 classes — Polyplacophora (chitons), Gastropoda (snails, slugs, nudibranchs, conchs & abalone), Pelecypoda or Bivalvia (clams, oysters, & mussels), & Cephalopoda (squid, octopus, & nautilus)


SNAIL, CLAM, CHITON, & SQUID

Class Polyplacophora
Characteristics

  • All marine
  • Have a shell divided into 8 over-lapping plates
  • Live on rocks along seashore feeding on algae


CHITON

Class Gastropoda
Characteristics

  • Head has a pair of retractable tentacles with eyes located at the ends
  • Have a single shell or valve (snails) or none (slugs)
  • Known as univalves
  • Snails
    * May be marine, freshwater, or terrestrial
    * Aquatic snails breathe through gills & use their radula to scrape algae for food
    * Terrestrial snails use their mantle cavity as a modified lung & saw off leaves
    * Retreat into shell in dry periods & seals opening with mucus
    * Have open circulatory system
    * Secrete mucus & use muscular foot to move
    * Land snails are hermaphrodites
    * Aquatic snails have separate sexes
    * Use internal fertilization

  • Slugs
    * Live in moist terrestrial areas
    * Lack a shell


SLUG

  • Pteropods
    * Called “sea butterflies”
    * Marine
    * Have a wing-like flap for swimming


“SEA BUTTERFLY”

  • Oyster Drills
    * Radula modified to drill into oyster shells


OYSTER DRILL

  • Nudibranch
    * Marine slug
    * Lacks shell


NUDIBRANCH

Class Bivalvia or Pelecypoda
Characteristics

  • Sessile or sedentary
  • Includes marine clams, oysters, shipworms, & scallops and freshwater mussels
  • Filter feeders
  • Have two-part, hinged shell (2 valves)
  • Have muscular foot that extends from shell for movement
  • Scallops clap valves together to move

  • Shell secreted by mantle & made of 3 layers — outer horny layer protects against acids, middle prismatic layer made of calcium carbonate for strength, & inner pearly layer next to soft body
  • Mantle secretes substance called “mother of pearl” to surround irritants like grains of sand
  • Oldest, raised part of shell called umbo
  • Powerful anterior & posterior adductor muscles open & close shell
  • Lack a distinct head
  • Have an incurrent & excurrent siphon that circulate water over the gills to remove food & oxygen

INTERNAL CLAM ANATOMY

  • Have heart & open circulatory system
  • Nervous system made of 3 pairs of ganglia, nerve cords, & sensory cells that detect light, chemicals, & touch
  • Separate sexes with external fertilization of eggs

Class Cephalopoda or Amphineura
Characteristics

  •  Includes octopus, squid, cuttlefish, & chambered nautilus  
  • All marine  

 

NAUTILUS OCTOPUS SQUID

 

  • Most intelligent mollusk
  • Well developed head
  • Active, free swimming predators
  • Foot divided into tentacles with suckers
  • Use  their radula & beak to feed
  • Closed circulatory system
  • Lack an external shell
  • Highly developed nervous system with vertebrate-like eyes
  • Separate sexes with internal fertilization

  • Squid
    * Largest invertebrate is the Giant Squid
    * Large, complex brain
    * Ten tentacles with longest pair to catch prey
    * Use jet propulsion to move by forcing water out their excurrent siphon
    * Chromatophores in the skin can help change squid color for camouflage
    * Can squirt an inky substance into water to temporarily blind predators
    * Have internal shell called pen
    * Female lays eggs in jellylike material & protects them until hatching


GIANT SQUID

  • Octopus
    * Eight tentacles
    * Similar to squid
    * Crawls along bottom looking for prey


OCTOPUS

  • Chambered Nautilus
    * Has an exterior shell
    * Lives in the outer chamber of the shell
    * Secretes gas into the other chambers to adjust buoyancy


NAUTILUS

Economic Importance of Mollusks

  • Used  by humans for food
  • Pearls from oysters
  • Shells used for jewelry
  • Do crop & garden damage
  • Serve as intermediate hosts for some parasites such as flukes
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