Mixtures, compounds & elements

[jennifer.]

Hi! I'm having trouble answering some questions on a lab I did in class. Any help at all would be greatly appreciated!

The purpose of the experiemt was to test the differences between pure substances (elements, compounds) and mixtures.
If the procedure would help, here it is:
1. Mix equal amounts of iron and sulfur and a piece of paper. Examine the mixture and record observations.
2. Separate the mixture into two parts.
3. Put one of these two parts into a test tube and add 4-5 drops of HCl.
4. Place the second portion in a dish and heat it for approximately 4-5 minutes.
5. Once cooled down, take a sample from the dish and add a few drops of HCl. Record observations.

The questions that I have to answer are: Which of the changes that took place in this experiment are physical and which are chemical? Why? Which of the substances were elements, which were part of a mixture, and which formed a compound?

Thank you SO much for any help! :)

 

[jennifer.]

can anyone help me?

 

[quicknote]

I can provide some insight and assistance with your questions. First, let's define the terms we are dealing with:

Mixtures - a combination of two or more substances that are physically combined and can be separated through physical means (e.g. filtration, distillation)
Compounds - a combination of two or more elements that are chemically bonded together in a fixed ratio and can only be separated through chemical means
Elements - pure substances that cannot be broken down into simpler substances by chemical means

Based on the experiment procedure, we can see that the mixture of iron and sulfur is a physical combination, as it can be separated into its individual components. The separation of the mixture into two parts is also a physical change.

Adding HCl to the mixture in the test tube and heating the mixture in the dish are both chemical changes. The addition of HCl causes a chemical reaction between the acid and the iron, producing iron chloride and hydrogen gas. The heating of the mixture causes a chemical reaction between the iron and sulfur, producing iron sulfide.

In terms of substances, iron and sulfur are both elements. The mixture of iron and sulfur is a mixture of two elements. The addition of HCl to the mixture in the test tube forms a compound - iron chloride. The heating of the mixture in the dish also forms a compound - iron sulfide.

I hope this helps you understand the concepts of mixtures, compounds, and elements better. Remember, if you have any further questions or need clarification, don't hesitate to ask your teacher or a fellow classmate. Science is all about asking questions and seeking answers! Good luck with your lab report!