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Over the summer, I teach chemistry and biology to middle schoolers who are hoping to go to private school. The classes are about hour-long with limited supplies. What are some chemistry labs or experiments that can be done on a budget in the classroom?

Hi Kristina!  A great and cheap activity I've done in the past was to use pH paper and water testing kits to have the students test water.  They can start with tap water and then move to rainwater or water from a local stream.  This can lead to discussions about water treatment and what causes treated water and natural source water to be different. Usually, testing kits have a color wheel or color test cards for comparison purposes.  The results can be logged into each student's 'lab book.'

Another great activity is to make seawater from aquarium salt and then compare the chemical properties of each, such as boiling point, density, and salt exclusion. For a start, boil each sample and see if the boiling point is the same using a thermometer.

Use small cups to freeze a sample of fresh water and seawater and compare the properties after a day. Does fresh water and sea water have the same freezing point? 

Then, put the samples back in the freezer until they are both solidly frozen and then put a drop of food coloring on each sample.  The food coloring will go around the fresh water sample but go through the seawater sample due to salt exclusion, which happens because of the exothermic reaction of the salt making small tunnels through the ice.  Ask the students if they think an iceberg is less salty than seawater.

If you use different colors for the fresh and seawater, you can put the ice cubes in a small aquarium filled with fresh water at room temperature and the ice cubes will melt and the colored seawater will sink to the bottom due to higher density. 

If you are careful and put the seawater sample in first, it will go to the bottom and make a colored layer.  Then put the fresh water sample in and it will make a layer on top of the seawater layer.  Then, you can talk about water circulation in the oceans of the earth based on density and salinity.

Have fun.  

Hi Kristina!  I'm reposting because my profile didn't appear correctly.  Sorry!

A great and cheap activity I've done in the past was to use pH paper and water testing kits to have the students test water.  They can start with tap water and then move to rainwater or water from a local stream.  This can lead to discussions about water treatment and what causes treated water and natural source water to be different. Usually, testing kits have a color wheel or color test cards for comparison purposes.  The results can be logged into each student's 'lab book.'

Another great activity is to make seawater from aquarium salt and then compare the chemical properties of each, such as boiling point, density, and salt exclusion. For a start, boil each sample and see if the boiling point is the same using a thermometer.

Use small cups to freeze a sample of fresh water and seawater and compare the properties after a day. Does fresh water and sea water have the same freezing point? 

Then, put the samples back in the freezer until they are both solidly frozen and then put a drop of food coloring on each sample.  The food coloring will go around the fresh water sample but go through the seawater sample due to salt exclusion, which happens because of the exothermic reaction of the salt making small tunnels through the ice.  Ask the students if they think an iceberg is less salty than seawater.

If you use different colors for the fresh and seawater, you can put the ice cubes in a small aquarium filled with fresh water at room temperature and the ice cubes will melt and the colored seawater will sink to the bottom due to higher density. 

If you are careful and put the seawater sample in first, it will go to the bottom and make a colored layer.  Then put the fresh water sample in and it will make a layer on top of the seawater layer.  Then, you can talk about water circulation in the oceans of the earth based on density and salinity.

Have fun.