What changes and what stays the same when salt dissolves in water?
4. Dissolve salt in water
Tracking dissolved salt using weight
![Students mixing cup of salt and water](../../img/5CFT_MCoC_Sp10_I05_27_small.jpg)
Distribute the second set of materials to the groups.
The Science Notebook page [What happens when salt dissolves in water?] will guide students through the process of weighing the water, salt, and the water with the salt added, and tracking changes in the volume.
- Review the concept of tare weight. Call attention to the tare weight of the cup, which you have posted.
- Show students where to put a piece of masking tape on the water cup so they can mark the water level before adding the salt.
- Review the notebook page that sets out the procedure for recording the weights. The weight data will be numerical (grams); the volume data will be visual (labeled drawings).
- Students will discuss their findings after they weigh their mini-lakes.
As students finish collecting and recording the data, collect the 12oz cups of salt water and have students get their mini-lakes.
Transforming mini-lakes to Salt Lakes
![Students adding salt to mini-lake](../../img/5CFT_MCoC_Sp10_I05_31_small.jpg)
Students have probably heard about the Great Salt Lake in Utah. They'll now have the opportunity to transform their mini-lakes into Mini Salt Lakes by adding two teaspoons of salt.
Tell students they'll need to weigh their mini-lakes twice: once before adding the salt and once after adding the salt.
Distribute the third set of materials, 1 12oz cup holding approximately 20g of salt, to each pair.
Each pair:
- Weigh mini-lake and record weight in Science Notebook.
- Pour salt into mini-lake. Don't stir.
- Re-weigh mini-lake and record weight in Science Notebook. Add a note about addition of salt.
- Calculate the weight of the salt added to the mini-lake and record in Science Notebook.