4c. Cabbages, Acids, and Bases!!

The Experiment

In this experiment we had to determine the identity of two unknown solutions. We had to figure out if they were weak or strong acids or bases or neutral solutions. To do this we cut up some red cabbage and put it in a beaker with water just covering it. Then we  boiled it so that the juice from the cabbage went into the water. We then strained the cabbage out, leaving only a purplish liquid, an indicator. We put the indicator in the different liquids- a strong acid, a weak acid, a strong base, a weak base and a neutral liquid. We knew that acidic liquids turn red, basic liquids turn greenish-yellow and neutral liquids turn purple or blue. From this knowledge we could determine the identity of the two mystery liquids.

The liquids and their colours

Pure water- blue

Weak acid- pink

Strong acid- red

Weak base- turquoise

Strong base- yellow

Determining the identities of two unknown solutions

Solution 1: This liquid is blue, meaning it is neutral.

Solution 2: This liquid is yellow, meaning it is a strong base

How many times stronger would an  acid with ph1 be compared to the acid with a  pH of 3?

An acid with a pH of 1 is 100 times stronger than  an acid with a pH of 3. This is because each pH number is separated by ten times more strength. For example, an acid with a pH of 1 is 10 times stronger than an acid with a pH of 2 and an acid with a pH of 2 id ten times stronger than an acid with a pH of three 3.

4b. Neutralizing Acids and Bases

The Experiment

For this experiment we had a few drops of indicator in a beaker and we had to put in some acidic liquid and neutralize it. Then we did the same again but witha  basic liquid.

Neutralizing an acid

To neutralize an acid that had a pH of 1, we added some basic liquid to it and kept adding a few drops of each liquid until it was a brownish liquid with a pH of about 7, meaning neutral.

Here is a pucture of the acid that we neutralized:

Neutralizing a base

To neutralize a base with a pH of 14, we added some acidic liquid to it and kept adding drops of the two liquids until it too was a brown colour with a pH of 7 too.

4a. Acids and Bases

The pH scale

This is the pH scale which determines how acidic or basic various liquids are. It oes from 0 to 14. A pH of 7 is neutral,  a pH less than 7 is acidic and a pH greater than 7 is basic. Here is a picture of the ph scale with some examples for each number.

The experiment

For this experiment we put pieces of pH paper in a dish with little bowls in it and then added 13 liquids, 1 for every piece of paper. We mannaged to find out how acidic or basic the liquid was by looking at the colour the pH paper turned when the chemical was added. If it went blue or green it was basic whereas oranges and reds were more acidic (see the pH scale above.)

Liquids and their place on the pH scale

1. Pure water- 6
2. Tap water- 9
3. Drain cleaner- 14
4. Soap- 6
5. Vinegar- 2
6. Orange juice- 3
7. Coke- 2
8. Baking soda- 9
9. Stomach/hydrochloric acid- 1
10. Ammonia- 12
11. Vitamin C- 2
12. Milk- 6
13. Lemon juice- 1.5
14. Spit- 6

Which substance given is the most acidic?

The stomach/hydrochloric acid was the most acidic liquid.

Which substance is the most basic?

The drain cleaner was the most basic liquid.

3b. Rates of Reaction

What is a catalyst?

A catalyst is a substance of any kind that speeds up or slows down a chemical reaction without itself being affected. They can be organic, synthetic or metal. The process by which the catalyst speeds up or slows a reaction is called catalysis.

Determine which food group (liver, celery, potato, bread) is the best and the worst catalyst for the decomposition of hydrogen peroxide.

Out of the four foods we tested, liver , celery, potato and bread, the liver proved the most successful at decomposing  the hydrogen peroxide. When the acid came into contact with it, it fizzed up and came up the test tube and bubbles came right out the top! The potato  was the second most effective, then the celery and finally the bread.

The Decomposition of hydrogen peroxide

When hydrogen oxide is decomposed it turns into oxygen and water. If a glowing splint is put into the test tube with liver and hydrogen peroxide so that it isn’t touching them but is still in the test tube, the oxygen will cause it to be re-lit!

3a. Rates of Reaction

How does concentration affect the speed of the reaction?

If there is a higher concentration of a given substance the chemical reaction is quicker. The experiment we did to test this was to add calcium carbonate rocks to hydrochloric acid. In one test tube we had 5ml of acid and in the other we had 7ml of acid. The result was that the one in the 7ml of hydrochloric acid dissolved faster than the other one with only 5ml of acid.

How does surface area affect the speed of the reaction?

A larger surface area provides a quicker reaction. The experiment we did to test this was to take 1 teaspoon of calcium carbonate powder and add it to 5 ml of htdrochloric acid in a test tube and take a rock (which had a smaller surface area) and add that to 5ml of acid in a different test tube. Even when the powder had finished reacting, the rock was still fizzing away. The powder, with the larger surface area, had a much faster reaction.

How does temperature affect the speed of the reaction?

we found that the colder the liquid is, the faster the reaction occurs. The experiment we conducted in order to test this was heating up one test tube with 5ml of hydrochloric acid in a beaker of water and keeping the other test tube, also with 5ml of acid, cold. The hot one was 30 degrees Celsius and the cold one was 25 degrees Celsius.  Then we added a teaspoon of  calcium carbonate powder to each test tube and the cold one reacted quicker. We were very surprised by our results and when we asker our teacher, she said that our results were incorrect and that in fact, the hot one should have reacted faster.

Detailed question-

How does concentration affect the speed of the reaction?

Observations and results

• Both acids fizzed immediately when the acid was put in to them.
• They both became a white liquid that looked a bit like milk after the fizzing had stopped.
• The more concentrated acid had a faster reaction.
• All three trials had similar results.

Data

In the table below is the data from our experiment

 

Conclusion

My hypothesis was that the more concentrated liquid would have the fastest reaction because I thought that the more acid there was, the quicker the powder would dissolve. If the acid was diluted, there would not be as much of it to help dissolve the powder. This proved correct as the 10ml of acid only took an average of  14.3 seconds to finish reacting whereas the diluted acid, with 5ml of acid and 5ml of water, took an average of 22.6 seconds to finish reacting. I think we got these results because of the reason I stated above, that the more acid there is to help dissolve  the powder, the quicker the reaction is.

Some errors that were in this experiment were the following:

• The timing was not very accurate. We used stopwatches and probably did not start at exactly the right time or stop at the right time. It was quite hard to see when to stop because you could not always see the bubbles because it was a white liquid and hard to see. This would have affected our results.
• Our measurements might not have been completely accurate every time. We tried to use the same amount of powder each time- 1 flat teaspoon full- but it would still have varied slightly from time to time.

If we re-did this experiment, there would be several things that we would change to make this experiment more accurate. First of all, we would need to make the timing more accurate. This would be challenging because it is so hard to see the bubbles in the white liquid and to determine when the reaction is over. This could be achieved by videoing the experiment and then watching it in slow motion sso that we could determine the exatc time it took the reaction o take place. Secondly, we would need to make sure we always had the same amount of calcium carbonate powder. We could do this by weighing it instead of measuring it out in a teaspoon. Finally, we could do a bigger experiment with more trials so that we would have more data to draw a more accurate conclusion. All of these would make the experiment much more accurate.

2b. Covalent Bonds

The Experiment

For this experiment we had to measure out 5ml of hydrochloric acid and put it in a test tube. Then we added a 2cm long piece of magnesium to the acid and quickly put a piece of card over the top of the test tube in order to allow the hydrogen gas to collect in the tube. After about 30 seconds we removed the card and quickly put a burning match at the top of the test tube. The match made a popping sound and went out.

What are covalent bonds?

Covalent bonds are a type of chemical bonding which happens when atoms share  pairs of electrons. It is different from ionic bonding because, rather than transferring electrons, they share them. This usually happens between non-metals and they will share electrons, trying to both fill their valence shells.

What is the product of burning hydrogen and oxygen?

The product of burning hydrogen and oxygen is water.

What is happening to the electrons to form these new covalent bonds?

The electrons are being shared, and making each atom have a full valence shell. 

Draw the electron arrangement of the product

As you can see in the image above, the 1 oxygen and 2 hydrogen atoms are sharing electrons. This is a covalent bond.

2a. Ionic Bonds

What are ionic bonds?

 An ionic bond is a chemical bond between a metal and a non-metal. The metal gives an electron to the non-metal making then oppositely charged.  The metal becomes positive and the  non-metal becomes negative. And then, because opposites attract, an ionic bond is formed.

Why do noble gases not form bonds with each other or other types of atoms?

Noble gases do not form bonds with each other or any other atoms because they are already stable and have eight electrons on their outermost orbit. This means that they cannot gain any electrons.

What is the Product?

When magnesium burns in oxygen it burns with a bright white light and magnesium oxide is formed

Magnesium + Oxygen->Magnesium oxide

2Mg +O2->MgO

What are the electrons doing to form this ionic bond?

The electrons are being transferred from the magnesium to the oxygen. This forms the ionic bond.

Draw the product showing what happened to the electrons

The magnesium gives the oxygen the two electrons so that the oxygen has a full orbit of electrons. It also does because the orbit under the one it had is full.

1b. Making Alcohol

We were given the task of making wine. To do this we mixed grape juice with yeast and now we are letting it sit for a few days in order to turn it in to wine. During this process, a chemical reaction will take place. The yeast will eat the sugar and it will multiply. Then it will give off two waste products- alcohol and carbon dioxide. When there is a certain concentration of alcohol, the yeast disappears. Because of this, when you are drinking wine, you are drinking yeast poo.

After allowing it to sit for a while, we tested that it was alcohol by distilling it and then burning it. It produced a whiteish flame, proving that we had made alcohol.

1a. Chemical reaction in a bag

Observations- When we tipped the phenol red over the baking soda and calcium chloride, an immediate reaction took place. The two powders started fizzing and  frothing and turned orange as the red liquid hit them. At the same time, they gave of carbon dioxide which made the bag puff up so that it looked like a balloon. When we touched the liquid, we felt that it was creating immense heat which surprised us. We waited a while and the bag deflated a little and the bubbles in the orange liquid began to disappear. After a while, there was only a puffy bag with an orange liquid without bubbles in it.

Answer- This chemical reaction was exothermic. Exothermic means that it gives off heat and this did.