10 October Science 8 Crystals, chemical reactions, evidence for atoms and molecules

  1. Mindful moment. Think of the science journey in a chemical reaction. Think of the river you will ride on WOW 8.
  2. Review previous DSN. You now have investigated a bit from two chemical reactions.
  3. Preview today’s plan on the current blogpost.
  4. Create your DSN entry for today in the Matter folder.
  5. Questions.
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Do you think this works? Try it.






















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A. Make a (super-) saturated solution using hot water. We will bring you 50 ml of hot water. Dissolve as much substance as you can in a beaker. Start with one spoonful. Pour only the liquid in a labeled petri dish; do not pour any solid material into the dish. Set the dish on the back country in a tray. Be careful not to spill any solution. Work neatly. Do not contaminate supplies. Clean spoons, glassware thoroughly before trying a different substance. Choose 2 different substances from this list. Be sure to label your petri dish with names, period, date, substance. (Remember that you have already observed Sodium Chloride crystals.)

Substances (Only use what you need. Do not inhale. Avoid contact.) :

  • Copper Sulphate                              CuSO4
  • Zinc Sulphate                                   ZnSO4
  • Aluminum Potassium Sulphate   KAl(SO4)2
  • Magnesium Sulfate                         MgSO4
  • Cobalt Sulphate                                CoSO4

B. With your partner, get a microscope, slide, and small piece of copper. Place the copper on the slide and bring it into focus on the lowest power. Try to take a picture with your ipad. When you are ready, we will put a drop of silver nitrate solution on the copper piece on the slide. Continue to observe carefully. Take pictures as you can. What do you see happening.

Timelapse by Denzel C. period 8 Science 8 10 October, 2018: <https://drive.google.com/file/d/1FAY6QMXNpnwFwAf62qLE-mIpTG9nptEr/view?usp=sharing>

Here is a depiction of the reaction. S means solid. Aq means aqueous–in water–a solution:

copper + silver nitrate → copper(II) nitrate + silver
Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

The numbers give the ratio of atoms that combine. Notice that the same number and kind of atoms appear on each side of the reaction. This is why this expression is called an equation.

Try a similar observation with a piece of zinc. Here is the reaction equation:

Zn(s) + 2AgNO3(aq)Zn(NO3 )2 (aq) + 2Ag(s)

C. If time, we will try to observe Brownian motion. If no time, next class.

We will examine Brownian motion of fat globules in milk. See what you can find out about Brownian motion. The technique will be described in class.

See the videos showing Brownian motion of fat globules in milk. Apologies for the camera motion. The videos would have been better with a fixed camera. Nevertheless, it is possible to see the random movement of the fat globules. How is this movement interpreted in light of the atomic/molecular theory of matter? (Note: a microscopic fat globule is composed of a truly enormous number of too-small-to-see molecules–according to the theory.)

Video https://drive.google.com/file/d/0B4DPwlouN3dIRHQ0NUw5RWtpNzg/view?usp=sharing

D. Create and complete this chart with our class investigations to date:

Consider these big questions (KEEP IN VIEW-KIV QUESTIONS AND IDEAS):

  • What can we observe about the structure and behavior of matter?
  • How can we explain what we observe (at the scale of our senses) by structures, entities, and behaviors at a scale we cannot see?
  • How can such explanations be tested?

List all the activities and investigations

we have carried out with matter.

How can these be explained in terms of

the behavior and properties of atoms?

A few examples of large scale observations:

  • Water changing state. Temperature plateaus.
  • Salt water evaporating more rapidly than fresh water.
  • Conservation of mass–mass of ice  equals mass of melted water.
  • Crystal form of Sodium Chloride.
  • Solutions of magnesium sulphate and sodium carbonate reacting.
  • Vinger and baking soda reacting.
  • ETC.

E. The video recommended earlier in the year demonstrates how to take an observation of matter in the large scale and explain it in terms of what happens on the atomic scale. You should watch it if you have not already AND it is good to watch again: From The Ring of Truth by Philip Morrison. Atoms: https://www.youtube.com/watch?v=WQ3mjb9BSaU

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