## How many drops of water can fit on a penny?Investigation# 1.1 Biology 4-Naomy Bonilla-2/13/17

### Introduction

What we are trying to find is how many drops of water can fit on a penny. Our hypothesis was 8 drops of water can fit on a penny. We thought this because a penny is small, so we didn't many drops of water would fit o the penny. Also we didn't think that the hydrogen bonds would hold many water molecules together.

### Materials

• One penny
• An eyedropper
• Pair of tweezers
• Sample of testing liquid (water & soap)
• clean water source for rinsing pennies
• Plenty of paper towels

### Procedures part A:

1. Rinse penny in tap water and dry completely
2. place penny on paper towel
3. use the eyedropper to place drops of water on the penny (one at a time ) until any amount of water runs over the edge of the penny
4. Record the number of drops for the trial

We conducted four trials before averaging them up.

Number of trials:

1. 33 drops
2. 11 drops
3. 36 drops
4. 30 drops

Average: 27.5

### Procedures Part B:

1. Start with clean penny, rinse in tap water and dry completely
2. Hold penny with the tweezers provided, then dip it into the soap (testing liquid) Allow all extra liquid to drip into the container provided.
3. Place the penny on the dry spot on the paper towel,place drops of water on the penny (one at a time ) until any amount of water runs over the edge of the penny.
4. Record observations on the table

Number of trials:

1. 23 drops
2. 33 drops
3. 23 drops
4. 30 drops

Average: 27.25

### Discussion

1) Explain Your results from both parts of the experiment in terms of cohesion and surface tension.

1) The water drops on the penny attracted water molecules because they were of the same substance. After the soap was added the water molecules didn't attract as much because the composition of the water has changed. Due to the weakness of the hydrogen bonds the molecular weight had less molecular mass therefore making it easier for the surface tension to break

2) How do your results compare to other groups in your class? Provide at least 2 possible reasons for any similarities and differences you identified.

2) It all depends on how much force was used to press the dropper on to the penny . Next is how fast or slow the dropper was pressed.

### Conclusion

What we studied was how may water drops can fit on a penny. What we found out was many drops of water could fit on a penny because of cohesion and surface tension. The reason for this is because of cohesion the water molecules formed hydrogen bonds, and because of the surface tension that forms from the hydrogen bonds the penny could hold many drops of water. We learned that with water as the only substance tested the cohesion and surface tension was greater, but after the soap was added the cohesion and surface tension lessened. If you want a higher amount of water drops on the penny i suggest you take your time and do not be nervous.

Credits: