Investigating Solubility

Forensic scientists analyze samples used as evidence during an investigation. This week at After School To-Go, students used a similar method to figure out the source of a note, which was written in black marker. Before conducting their analysis, girls reviewed concepts like solubility, solvents, solutes, and mixtures.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Girls were shown 2 pieces of paper with writing in black marker, they were asked if they could tell which was written with permanent marker and which was in washable marker. It was extremely difficult to tell the difference based on a visual observation alone, so girls were given coffee filters, black markers, and water in order to find the answer. The coffee filters were marked with different black markers then dipped in the water. Because some pigments can dissolve better in water than other, less water-soluble pigments, each marker stain looked unique!

 

 

 

 

 

 

 

 

 

 

The students then tested their chromatography method on each other by writing notes in black markers and trading them with other tables. By observing the marker stains, each group was able to match the note with the group of girls who wrote it!

Drops on a Penny

Water is everywhere – we drink it, swim in it, use it to wash our cars and keep our plants alive. Because it’s such an essential part of our daily lives, sometimes we can take the amazing properties of water for granted. This week at Girlstart, students learned about one very cool characteristic of water: its surface tension! Week 3’s activity was based on the hydrologist career, which involves the movement of water in the Earth’s crust. Hydrologists use lots of models and computer simulations, but also spend time wading in lakes and rivers to collect samples.

For their activity, girls measured the number of drops that can fit on one penny. Before they began, girls made hypotheses based on the size of a penny: 1, 2, 3 drops? After running three trials, students were surprised to learn that the answer was closer to 20 drops!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The students conducted the same tests, this time using other liquids such as lime juice or vegetable oil. After observing the averages, students were able to see that the cohesion between H2O molecules creates incredibly strong surface tension!