THIRD EXPERIMENT: pH

• Introduction:

The pH is a mesure of the acidity or basicity of a solution. solutions with a pH less than 7 are basic or alkaline. pure water (distilled water) has a pH close to 7, neutral. 

pH=-log(H⁺)

• Materials:

1. Distilled water.
2. Milk.
3. Wine.
4. Lemon.
5. Tomato.
6. Coffe.
7. Carbonated beverage.
8. 10% NaOH solution.
9. 10% HCl solution.
10. NH₃ solution.
11. Soap solution.
12. Universal indicator paper (trips).
13. pH-meter.
14. Acetic Acid.
15. Tongs.
16. 8 x 100 ml Bgeakers.
17. 2 Clock glass.
18. 1 x 250 Beaker.
19. 5 test tube.
20. Test tube rack.
21. 10 ml Pipet.
22. Funnel.
23. Graduated Cylinder.
     

• Procedure.

To mesure the pH of different solutions we are going to put the different solutions in small beakers of 250ml.

1. Squeeze the lemon and tomato in tho clock glasses.
2. Take a piece of indicator paper and place one end of it into the solution. Leave for at least 20 seconds.
3. Remove the indicator paper and compare its a colour with the appropriate colour chart.
4. Repeat points 1 to 2 with as many others solutions as you are provided with.
5. Record your results in a results table in your worksheet.

How does concentration affect pH?

Squeeze the rest of the lemon inside a beaker and filter the solution with a funnel and cellulose paper.

     6. Prepare a test tub rack with 5 test tubes cleaned with distilled water. Mark the tubes with the labels: A, A1, A2 and B.

     7. Add 10 ml of lemon juice to tubes A and B.

     8. Take the A tube and put 5ml of its lemon juice to the test tube A1.

     9. Take the A1 tube and put 2,5ml of its lemon juice to tube A2.

     10. Take the A2 tube and put 1.2 ml of its lemon juice tu tube A3.

     11. Add distilled water to each test tube until it has the same volume as test tube B (10ml).

     12. Calculate tehe concentration of each test tube with the formula you have below:

                          Concentration(%)= (Volume of juice/ Total Volume) x 100

      13. Find the pH of each of the test tube and record the information in the table:

  

Test	Volume of	Total	Concentration	pH
B	10 ml	10 ml	100%	3,38
A	5ml	10 ml	50%	3,35
A1	2,5 ml	10 ml	25%	3,37
A2	1,25 ml	10ml	12,5%	3,33

14. Graoh your results on graph paper for the pH of different tubes (concentrations). Be sure to include the following: Title, clearly labeled X and Y axis, use a ruler and colored. To publish it in your blog, tou can do it in Excel or take a picture with you mobile device.

 

 The results should have been others but the pH meter is unbalanced.

•  Results or Observations:

When we placed the strips in the different compounds could be differentiated differents colors therein.

And in the experiment of lemon juice having different concentrations of juice, the pH-meter pH told different numbers.

• Conclusions:

Placing the strips in the various compounds note that in each a different color product devido their acidity, neutrality and basicity out.

• Questions:

1. Which of the solutions gave an acid pH? HCl, vinegar, wine, tomato, cofee, milk.
2. Which of the solutions was alkaline? Soap, Bleach, NaOH:
3. Which of the solutions Were neutral? Did you expect these results? Explain. Distilled water. Yes, because it has no minerals.
4. How does a pH of 3 differ from pH of 4 in terms of H⁺ concentrations? The value is ten times.
5. In the second part of the experiment, you have compared the pH of the same product (lemon juice) in teh different concentrations. In this case explain:

                 a. Which is the dependent variable? The pH.

                  b. Which is the independent variable? The lemon concentration.

                  c. Which is the problem that we want solve?Know which is the pH at different concentrations.

                  d. Which is the control of the experiment? The tube B.

     6. Which pH do you think that gastric juice might have?Why? Do you think that intestinal pH has the same pH? Why? An acid pH, because gastric juice has compond for hydrochloric acid. No, because it has to unpack the food.

     7. Which pH do you think that blood might have? Why? A neutral pH, because this crossing the body and can not be acid.

     8. What is acid rain? Which are the consequence in the ecosystems and how is its formation pattern? Is rain In Bracelona aid or alkaline? Acid rain is when pollution affects the composition of the clouds and the water gets more acidic than normal.It can affect the ecosystem, killing plants and trees. The Barcelona is acid rain as it is a central city where mucho The Barcelona is acid rain as it is a central city where much CO₂ is emitted.

SECOND EXPERIMENT: Osmosis

• Introduction:

Osmosis is the spontaneous movement of solvent molecules through a semipermeable membrane into a regino of higher solute concentration (hypertonic) in the direction that tends to equalize the solute concentrations on the two sides.
When the extracelular concentration is hypertonic, water moves out of the cell and the cell becomes flaccid: PLASMOLYSIS.
When the extracellular concentration is hypotinc, water moves inside the cell and it becomes TURGID.

• Material:

1. Egg
2. Potatoe
3. Salt
4. Distilled water
5. Acetic acid (or vinegar)
6. Spatula
7. 600 ml Beaker
8. 3 Clock glass
9. Pen
10. Spoon
11. Knife

• Procedure:

Egg: this experiment will be divided in two days.

Under the hard outer shell of a chicken egg is semipermeable membrane that allows air and moisture to pass through. Because water molecules can move into and out of the egg but larger molcules cannot, the semipermeable egg membrane allows for an explorations of concepts of diffusion and osmosis.

1st Day:
Before the egg osmosis experiment could begin, the egg's hard outer shell must be removed. Let's start with this:

1. Take a 600 ml beaker and put inside the egg.
2. Cover the egg with vinegar and make note of what's happening. Remember our last experiment!

Once the egg's shell is removed and the egg is rinsed dry and clean, measuer and weigh the egg. Record the dimensions of each egg in a table.


     3. Clean the beaker and put the egg inside again.
     4. Cover it with distilled water. Make note the volumen of solution inside the beaker.

2nd Day:

      5. Left the egg one day in the distilled water. After about a day, carefully remove the egg using a spoon. Rinse the egg with water and let it dry.
      6. Measure again the dimensions and records its weight.
      7. Make note of the solutions volume in the beaker and notice if there has been any difference.
      8. Observe the results and write your conclusions in your lab worsheet.

Potato:

1. Lay out three watch glass.
2. Slice the potato in three parts lengthwise. Each slice must be of 1'5 cm thick
3. Place each slice onto a watch glass and make a hole in the middle of each slice. NOTE: the hole does not have to cross the slice!
4. In the first slice hole, don't put anything. The second fill it with salt and the third with distilled water.
5. Left this preparation 30 minutes and makes note of what is happening.

• Resolts or Observations:

Egg:
When put the egg in shell the acetic acid and desace semipermeable membrane disappears and remains. Put the egg in distilled water and await the outcome for about one day, we can see that the egg has puffed up and has gained weight. Later we put the egg in water mixed with a high salt concentration and can see that the egg has been deflated and lost weight.

Potato:
Cut three pieces of potato, and put them in the three watch glasses. In a piece we do nothing, another put salt and put distilled water in another.
In the piece that we do not put anything on potato oxidized in the piece we put salt water and expels potato gets soft, and the piece that we distilled potato absorbs water and becomes turgid.

• Conclutions:

The shell is undone by the following reaction: CaCO3 + CH3COOH = Ca (CH3COO) 2 + CO2.
The egg to be swollen in distilled water because the higher salt concentration inside the egg and water enters inside. When we place the egg in water with a high concentration egg devido deflates within the egg that is a lower concentration of salt outside.
All this is given to a balance of salts beyond.

• Questions:

1. What is happening when the shells are soaking of acetic acid? We see some bubbles the reactions: CaCO3+CH3COOH=Ca(CH3COO)2+CO2.
2. Explain the results of this experiment: The control grup there's no change. The salt grup expulsed water and lose turgense. The distilled grup absorbe water and win turgense.
3. Why have we left the first slice without any treatment (salt or distilled water)? To compare the all resolts.
4. Wich are the dependent and independent variables? The variable independent treatment(salt and distilled water) and variable dependent the form of cells or presence of water.
5. How can you explain (throught osmosis) the ability of plant roots to draw water from the soil?The salt concentration is higher in the cells and the water goes up because there was a balance.
6. What will it happen if a saltwater fish is placed in a freshwater (low concentration of salts) aquarium? It will die.
7. Look the image you have below and explain what is happening to the erytrocytes in each situations:In the first photo shows a case hypotonic, and is a plasmolysis in the second case Isotonic and hypertonic third case where a picture is turgidity.



FIRST EXPERIMENT: Chicken or lambs bones and egg/ Mollusk shells.

• Introduction:

Even though bones very light, they are also very strong. However, how strong they depens on how much of the minerals calcium carbonate (CaCO₃) they contain.

During foetal development, strong fibbers of collagen protein form a matrix for bones. The matrix is shaped like bones but is very flexible. The matrix solidifies by a process called calcification. Durins this process, calcium phospate or hydroxyapatite is deposited in the fibbers of collagen and gives the bones strength and rigidity.

• Material:

1.  Dried, cleaned chicken or lamb bones and egg. Some mollcuscs' shells.
2. Distiled water.
3. Vinegar and acetic acid.
4. 250ml Beaker.
5. Clock glass.

• Procedure:

Chicken or lambs bones:

1. Carefully clean and cut ad much of the meat away from the chicken thin bone as possible.
2. Examine tthe flexibility of the bone by trying to bend it with your fingers.
3. take a beaker and make and acid acetic solution or add vinegar.
4. Take the chicken or lamb bones and drop them in the acid acetic and vinegar solution that you have made.
5. Leave it 24-48 hours and see what happens to the bone. put a clock glass at the top of the beaker to protect the solution.
6. Remove the bones from the vinegar with a tong and soak them with water.
7. Write the results in your lab worksheet.

Mollusks shells:

1. Take another beaker and make the same acid acetic solution.
2. Put inside some shells and make note of what is happening.
3. write the observations in your lab worksheet.

• Resolts or Obserbations:

When we put the bones, egg and shells almost immediately we can see some bubbles coming up to the surface. And after several hours we can see how the shell of the egg disappeared and bones are not lost its rigidity.

• Conclutions:

The acetic acid and vinegar are dissolved organic matter and the bubbles that were detached at the beginning of the experiment is carbon dioxide caused by a chemical reaction. Have lost bone collagen and thus its rigidity.

• Questions:

1. Write the reaction that takes place when the acid acetic reacts with the calcium. CH₃COOH + CaCO₃ = CO₂ +Ca(CH₃COO)₂
2. What is happening when the shells are soaking of acetic acid? What are the bubbles that you can see? Drove a bubbles. The bubbles are carbon dioxide.
3. What is happening to the bones after some days of soaking it in acetic acid? Why is the bone flexible now? Lose rigidity. The bone is flexible because it loses calcium carbonate.
4. So, what is the fuctions of the calcium carbonate in the skeletal structures? Rigidity.
5. Increases in carbon dioxide to the atmosphere from the burning fossil fuels and deforestation threaten to change the chemistry of the seas. Evindence suggests that this increase in atmospheric carbon dioxide is lowering the pH of the oceans in a process called ocean acidication. How can acidifaction affects coral reefs? Coral reefs die and disappear.

 

• Photos: