How much salt and sand are there in a given salt-sand mixture? <---- What question is this trying to answer or what problem is it trying to explain? What list of procedures would you use to...

How much salt and sand are there in a given salt-sand mixture? <---- What question is this trying to answer or what problem is it trying to explain?

What list of procedures would you use to complete this lab in order?

What observations would you see in this project?

After this experiment, how would you answer the question based on the data?

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mr-mayonnaise | Middle School Teacher | (Level 1) Assistant Educator

Posted on

This type of question is attempting to discover the composition of a mixture by understanding the unique chemical structures of the parts. 

In order to complete this lab, I would submerge the mixture in water. This way, knowing the salt is soluble in water, I can dissolve away part of the mixture leaving behind the sand. I can use the change in weight and volume of the mixture from before and after soaking to find the amount of salt in the mixture. 

Procedure:

1. Prepare a container that can hold all of the sand/salt mixture with enough room left over for about 1 quart of water. Using a graduated container will allow you to find the volume pre-soak as well.

2. Zero out a scale with the empty container and pour in the salt/sand. Record the weight as your beginning weight before soaking. 

3. Add water to the mixture. You should add enough so the salt in the mixture is completely ionized and dissolves without overflowing and losing sand particles. 

4. Pour the wash through a filter. This should catch all of the much larger sand particles and allow the water and now dissolved salt to flow through, leaving behind only sand. 5. Repeat step 3 and 4 until you feel that all of the salt mixture has been thoroughly removed. 

5. Dry the sand using a heat lamp or allow it to stand in the sun for some time so water does not way the sand down and change your values. 

6. Zero out your scale and re-weigh your sand. This number should be the weight of the sand alone without the salt particles. 

7. Subtract the weight of the sand alone found in step 6 from the total weight found in step 2. This will give you the weight of the salt.

Observations:

  • Total weight of the mixture
  • Amount of water used (in case not all salt dissolves)
  • Weight of sand after soaking/drying
  • Weight of salt found from Total weight minus sand weight

Potential errors might include:

  • Not adding enough water to the sand/salt mixture and not all salt dissolving
  • Adding too much and washing sand down the drain
  • Using too fine a filter/too porous a filter
  • Not allowing the sand to dry long enough

The best ways to answer this question once the lab is complete are to give a weight comparison (sand weighed X, salt weighed Y), a volume comparison (sand took up X space, salt Y space), or a percent by weight/volume answer (X% of the mixture was sand, Y% was salt).

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