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Experiments

The A+ STEM Lab allows you to conduct over 400 grade-appropriate experiments that map to your curriculum. Use our library of videos to become familiar with how to use the tools in your lab to perform hands-on experiments with your students. Once you see how easy it is to use the probes and data loggers, your imagination will be the only limit of what you can try!


 

What happens when you add salt to ice?




 

Explanation:


Water freezes at 0º Celsius. Therefore, when you put a temperature probe in a cup of crushed ice (with a small bit of water), it will register a reading that hovers at just about 0º C.

When salt is added to the cup of ice, the temperature immediately drops by several degrees. Why does this happen? 

Salt water has a lower freezing temperature than plain water...it transitions between its liquid state and solid state at a lower temperature than plain water.  By adding salt to ice made of plain water, you now have ice made of salt water. The salt water ice cubes are in a solid state at a temperature that is too high for them to remain in a solid state. Therefore, they start to melt. The process of melting...transitioning from a solid state to a liquid state...requires energy. As energy is used and released to affect this transition, energy (heat) is released from the cup of ice, therefore lowering the temperature of the ice that remains in the cup.

Just think...the next time you melt the ice on your sidewalk by throwing salt on it, remember...you're actually making it colder!


 
 


What happens when you add baking soda to vinegar?

 
 

Explanation:


Vinegar is an acid. Acids are compounds that, when combined with water, break apart to form a hydrogen ion. (H+)

Baking soda is a base. Bases are compounds that, when combined with water, break apart to form a negatively charged hydroxide ion. (OH-)

When acids and base are combined, an acid-base chemical reaction occurs, as the OH- and H+ combine to form H2O (water). In the specific case of vinegar and baking soda, the combination creates water, carbon dioxide (responsible for the bubbles) and sodium acetate. 

When you add the two together in the garbage can and the reaction occurs, why is no carbon dioxide detected when you hold the probe over the can?

It's because the CO2 is heavier than the oxygen-rich air around it, so it settles within and around the cup, at the bottom of the garbage can. The probe, held above, doesn't sense it.

When you gently tip the cup as you remove it from the can, you are "pouring" the invisible CO2 into the can. And then,
when you tip the "empty" can over the CO2 sensor, you can see that the can wasn't empty at all! It had carbon dioxide inside!