Entry 4

Hi!

Today i had another laboratory lesson! It was really really interesting and definitely a very good hands-on experience. Today's practical was on Comparing Element, Compound and Mixture. 

Our aim was
1. to observe and compare the properties of compounds and mixtures made up of the same constituent elements.
2. Thus, infer some common characteristics of mixtures and compounds that can be used to distinguish them.

There were 2 parts to the experiment. The first part being (A): Investigating a mixture of elements. (B) Mixture or compound? Throughout the entire experiment we used two elements, that being Iron and Sulfur. We observed the appearances of both. The appearance of the Iron Filings was that it was silvery-grey and was in solid state. The appearance of sulfur powder was that it was yellow/ bright yellow and was also in solid state.

This was our experimental plan...
1. Place a spatula of iron filings and a spatula of sulfur powder on a piece of filter paper. Mix them together.
2. Move a magnet under the filter paper and observe if the magnet separates the mixture of elements.
3. Add the iron and sulfur mixture into a test tube of water. Stir the mixture and then let it stand for a while. Draw and label what you see.

That was for Part (A). After conducting the experiment, we answered some questions.
1. To form a mixture can the iron filings and sulfur be mixed in any proportion?
2. Feel the mixture(from the bottom of the filter paper). Does it feel warm?
3. Does water separate the mixture of elements?
4. Do the iron filings and the sulfur act as separate substances or a single substance with water?

Answers...
1. Yes, it doesn't matter because they are going to be mixed.
2. It remains cold, mixing the elements does not result in any heat change.
3. No
4. Separate substances.

Note that both elements are insoluble substances, so they are unable to dissolve in water.

In conclusion:
The substances in a mixture can be mixed in any proportion. When a mixture is formed, heat and light are not usually taken in or given out. The mixture can be separated by physical means. The mixture has/retains the properties of its constituent substances.

*Constituent= Individual substances that make-up the mixture*

Moving on to Part (B)...

1. Mix one spatula of sulfur and half a spatula of iron filings in a crucible
2. Cover the crucible with a lid and heat for 10 minutes using strong flame.
3. When the crucible has cooled down, open the lid and observe the residue left.
*** Sulfur burns in air readily to produce a poisonous gas, sulfur dioxide. 
->Keep the crucible covered during heating and remove the lid only after the crucible has cooled down 
-> Do not mix too much iron filings and sulfur (increases amount of poisonous gas produced) 

After the crucible has cooled down, i observed that the residue left was hard and black in colour, it was no longer in separate substances but mixed compound.

Conclusion 

Three things to note from this experiment
1. Properties of the compound have different physical properties from its constituent elements.
2. A compound cannot be separated by physical means.
3. A chemical reaction takes place when a compound is formed, when there is an energy change.

We were also given more enrichment questions...
For example: You are given a solid mixture of common salt, sulfur powder and iron filings. Describe how you will separate these 3 substances.

After much thinking and some background knowledge, i came up with this answer. Firstly, separate the iron filings first using a magnet. Then, add water to the mixture of sulfur and salt.The sulfur substance will float to the top leaving salt water. Use a filter to separate the salt water from the sulfur through a process called filtration. After that, reheat the salt water till it reduces to salt solid substance again. Lastly, Reuse the filter paper to squeeze out the water from the sulfur substance.

*A filter is used to separate insoluble and soluble substances. 

This was what i learned for the day! Thank you for reading again:)