Elements, Molecules & Compounds. 15/1/13

Comparing Element , Compound and Mixture. Partner: Emma :>

Element: 

• A Substance that cannot be spilt into two or more simpler substances by chemical reaction 
• Simplest kind of matter

Compound:

• A substance made up of two or more elements chemically combines together.

Mixture:

• Two or more substance which are not joined together chemically
• may be made up of elements, compounds or both
• May be solid, liquid or gas

Procedure and Observations:

Elements:

Appearance( Colour and State) of iron fillings: Slivery-grey powder

Appearance of sulfur powder: Yellow powder

Mixture:

Observations:
 

• Place a spatula of iron filings and a spatula of sulfur powder ona piece of filter paper. Mix them together. To form a mixture, can the iron filings and sulfur be mixed in any proportion?

       To form a mixture, the iron fillings and sulfur can be mixed in any proportion.

• Feel the mixture ( from the bottom of the filter paper.) Does it feel warm?

         The mixture remains cold  . mixture = no change in temperature

• Move a magnet under the paper. Does the magnet separate the mixture of elements?

         The magnet is able to separate the mixture of elements. Magnetic iron fillings. Non-magnetic sulfur

• Add the iron and sulfur mixture into a test-tube of water. Stir the mixture and let it stand of a while. Draw and label what you see.    Results: both are insoluble       
• Does water separate the mixture of elements?

          The water does not easily separate the mixture of elements. - Insoluble. cannot be separated easily           

• Do the iron filings and the sulfur act as separate substance of a single substance with water?

           The iron filings and the sulfur act as separate substances.      
Conclusions:

1. The substances in a mixture can be mixed in any proportion.
2. When a mixture if formed, heat and light are not usually taken in or given out.
3. The mixture can be separated by physical means.
4. The mixture has/ retain the properties of its constituent substances.

* constituent = individual substance that make up the mixture/ compound

Mixture of Compound

1. Mix one spatula of sulfur and half a spatula or iron filings in a crucible.
2. Cover the crucible with a lid and heat for 10 min. using strong flame
3. When the crucible has cool down, open the lid and observe the residue left. Describe the appearance of the residue. How is it different from the original iron fillings or sulfur
   • The new residue is heard and black solid. ( red= more sulfur. blue-= more iron)

   
   
4. Scrape out some reside from the bottom of the crucible on a filter paper and test it using a magnet. Does the residue separate into iron and sulfur with a magnet                                                  No. New residue has lost magnetic property (iron's property) -> New property. including new melting and boiling point.
5. Add the residue to water. Stir and allow the mixture to stand. Draw and label what you see.

6. Conclusion. Do you think the residue formed is a mixture / compound. Explain your answer

• Compound. Properties of a compound have a different physical property as its constituent element. 
• A compound cannot be separated by physical means. A chemical reaction takes place when a compound is form when there is a energy change -> heat content change/ heat transfer

Questions

1. A student decided to repeat the Part B of this experiment. But instead she used one spatula of sulfur and a spatula of iron filings. Predict what will this student observe with regards to ...

  

• Appearance of the residue in the crucible                                                                                  Mixture and black powder and excess grey iron filings

• Magnet test                                                                                                                                       Magnet os able to separate iron filings from black powder

• Residue in water test                                                                                                                              Grey iron filings and block powder will remain insoluble in water

• Explain your prediction                                                                                                                   Both iron and new compound are insoluble in water, producing a suspension as observed

Extension Question:

You are given a solid mixture of common salt, sulfur powder and iron filings. Describe how you will separate these 3 substances.

1. Use magnet to separate the iron filings from the mixture.
2. Add water to the salt and sulfur power mixture and stir. ( ensure that salt dissolved)
3. Filter the mixture (separate insoluble and soluble)
4. Evaporate the salt and water mixture to dryness ( remove all water)
5. Squeeze dry the sulfur and water mixture using the filter paper.

Learning Point from Practical:

In this experiment, i learnt the different properties of compounds and mixtures made up of the same constituent elements through comparing and observing. Also, I can infer some common characteristics of mixtures and compounds that can be used to distinguish them . (e.g. whether they can be separated through physical means.) 

Reflection: This experiment was really cool. I learnt the properties of compounds and mixtures through comparing and observing them in the process of the experiment . I was really excited when i could actually make/ create a compound through heating!

Questions: What are mixture used for? As in, for example, water is a compound made up of hydrogen and oxygen, but why is there a mixture of elements or compounds? Is it formed naturally or only by physical means?