L3. pH

Introduction:

The pH is a measure of acidity or basicity of a solution. Solutions with a pH less than 7 are said to be acidic and solutions with pH grater than 7 ara basic or alkaline.

For measuring the pH of a solution at the lab we have different pH indicators:

Universal indicator paper: it's an absorbent paper that has been impregnated with universal indicator. This method consists as a continuous colour change from about pH 2 to pH 10.

Ph-meter: is an electronic device used for measuring the exact pH of a solution. It consists of a glass electrode connected to an electronic meter that measures and display de pH reading.

Material:

- distilled water
- milk
- black wine
- lemon
- tomato
- coffee
- soap solution
- bleach
- 10% NaOH solution
- vinegar
- 10% HCl solution
- indicator paper
- ph- meter
- tongs
- 2 clock glass
- beakers
- 5 test tubes
- test tube rack
- 10 mL pipet
- funnel
- graduated cylinder

Procedure

Solutions:

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

1. Put into the beakers the milk and the black wine, and squeeze the tomato in a clock glass.
2. Take a pice of indicator paper and place one end of it into the solution. Leave for at least 10 seconds.
3. Remove the indicator paper and compare its colour with the appropriate colour chart.
4. Repeat points 1 and 2 with as many others solutions as you are provided with.
5. Record your results in a result table.

Lemon juice:

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

1. Prepare a test tub rack with 5 test tubes cleaned withe distilled water. Mark the tubes with the labels: A, B, A1, A2, A3.
2. Add 10 mL of lemon juice to tubes A and B.
3. Take the A tube and put 5 mL of its lemon juice to tube A1.
4. Take the A1 tube and put 2.5 mL of its lemon juice to tube A2.
5. Take the A2 tube and put 1.25 mL of its lemon juice to tube A3.
6. Add distilled water to each test tube until it has the same volume as test tube B (10 mL)
7. Calculate the concentration of each test tube with the formula you have below:

%= 100 x (volume of juice/total volume)

Questions

1. Which of the solutions gave and acid pH?

HCl, vinegar, black wine, tomato, coffee, milk.

2. Which of the solutions was alkaline?

Soap, bleach, NaOH

3. Wich of the solutions were neutral? Did you expect the results? Explain

Distilled water, yes I expect this results becouse distilled water doesn't have salts.

4. How does a pH of 3 differ from pH of 4 in terms of H+ concentrations?

10 vegades més gran

5. In the second part of the experiment, you have compared the pH of the same product (lemon juice) in different concentrations. In this case explain:

a. Which is the dependent variable?
pH o acidesa

b. Which is the independent variable?
concentracio de llimona

c. Which is the problem that we want to solve?
How does concentration affect pH?

d. Wich is the control of the experiment?
The tube that only have lemon (B)

e. Write the results and conclusions of your experiments:

Concentrations about lemon juice

Results

6. Which pH do you think that gastric juices might have? Why? Do you think that intestinal pH has the same pH? Why?
pH 2 becouse the gastric juice has HCl. I think intestinal ph is

7. Which pH do you think that blood might have? Why?

Neutral becouse the intern fluids need to have neutral pH.

8. What is acid rain? Which are the consequences in the ecosystems and how is its formation pattern? Is rain in Barcelona acid or alkaline?

The water contain more acid. The consequences in the ecosystems are the pollution.

material

L1. Osmosis

Introduction:

Osmosis is the spontaneous movement of solvent molecules throught a semipermeable membrane into a region of higher solute concentration that tends to equalize the solute concentrations on the two sides. Is a vital process in biological systems, as biological membranes are semipermeable. Water molecules travel through the plasma membrane in order to equilibrate the intra and extra cellular concentrations.

When a cell is submerged in water, the water molecules pass through the cell membrane from an area of low solute concentration to high solute concentration. When extracellular concentration is hypertonic, water moves out of the cell and the cell becomes flaccid: plasmolysis. When the extracellular concentration is hypertonic, water moves inside the cell and it becomes turgid.

Materials:
- egg
- potato
- salt
- distilled water
- acetic acid
- vinegar
- spatula
- 250 mL beaker
- 3 clock glass
- spoon
- knife

Procedure

Potato

1. Lay out three watch glass
2. Slice the potato in three parts lengthwise.
3. Place each slice onto a watch glass and make a hole in the middle of each slice. (the hole doesn't have to cross the slice)
4. In the first slice hole don't put anything, in the second you have to put salt and the third distilled water.
5. Left this preparation 30 minutes and make note what is happening.

Egg:

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

1. Take a 250 mL beaker and put the egg.
2.  cover the with vinegar (acetic acid) and make note of what's happening.

Once the egg's shell is removed and the egg is rinsed dry and clean, measure and weigh the egg.

3. Clean the beaker and put the egg inside again.
4. Cover with distilled water.

5. Left the egg one day in distilled wáter, after about a day, carefully remove the egg using a spoon. 

Questions

Egg experiment:

1. What is happening when the shells are soaking of acetic acid?

Bubbles

2. Write the results of the dimensions and weigh of the egg before and after immersing it in distilled wate. Write and draw a simple diagram of the water direction.

Potato experiment:

1. Explain the results of this experiments. 

Control: Doesn't change

Potato with salt: there are a lot of water

Potato with water: the water dissaper

2. Why have we left the first slice without any treatment?

To compare all the results

3. Which are the dependent and the independent variables?

dependent: the form of the cells

independent: tractment

General questions

1. How can you explain the ability of plant roots to draw water from the soild?

Perquè les cel·lules de la planta tenen sals i al possar aigua, l'aigua es dirigeix on hi ha més concentració.

2. What will it happen if a saltwater fish is placed in a freshwater aquarium?

It will die

3. Look the image you have below and explain what is happening to the erythrocytes in each situation. 

picture 1: plasmolisi

picture 2: isotónica

picture 3: turgencia

Egg with distilled water

Egg with disitilled water

weight egg

Egg without semipermable membrane

L2. Mineral salts in organisms

Introduction:

Event though bones are very light, they are also very strong. However, how strong they are depends on how much of the mineral calcium carbonate they contain.

When calcium carbonate and acetic acid combine, a chemical reaction takes place and carbon dioxide is released:

CH3COOH + CaCO3 -> CO2 +

Bones are made also of soft material, collagen. When bones are placed in the glass with acetic acid, this acetic dissolve the calcium carbonate so that only collagen is left. Collagen gives the bones strength and rigidity.

The objectives of the experiments are:     
- Identify mineral salts in organisms.
- Understand the function of inorganic biomolecules in skeletal structures of organisms.

Materials:

- Shells
- Chicken bones
- Distelled water
- Acetic acid
- Beaker (250 mL)
- Clock glass

Procedure:

Chicken bones:

- Clean and cut the meat away from the chicken bone
- Examine the flexibility of the bone by trying to bend it.
- Take a beaker and add vinegar.
- Take the chicken bones and drop them in the acid acetic solution (vinegar)
- Leave it 48 hours or maybe 72 hours and see what happens to the bone. Put a clock glass at the top of yhe beaker to preotect the solution.

Shells:

- Take another beaker and make the same acid acetic pure solution with distilled water.
- Put inside some shells and make note of what is happening.

Results:

Conclusions:

Questions:

1- Write the reaction that takes place when the acid acetic reacts with the calcium carbonate.

CH3COOH + CaCO3 -> CO2 + 

2- What is happening when the shells are soaking of acetic acid? What are the bubbles that you can see? 

Despren CO2 i bombolles 

3- What is happening to the bone after some days of soaking it in acetic acid? Why is thw bone flexible now? 

L'os és més flexible després d'uns dies ja que nomes queda el collagen.

4- So what is the function of the calcium carbonate in the skeletal structures? 

Rigility

5- Increases in carbon dioxide to the atmosphere from burning fossil fuels and deforestation threaten to change the chemistry of the seas. Evidence suggests that this increase in atnospheric carbon dioxide is lowering the pH of the oceans in a process called ocean acidification. How can adification affects corals reefs? 

A la llarga els coralls desaparareixeran ja que estan fets de carbonat calcic i el CO2 cada cop augmenta mes.

Egg shell with vinegar

shell with vinegarr

egg shell dissolt with vinegar

bone with vinegar