Books will be placed on the plunger of the syringe one by one and the volume of the gas will be recorded. This will illustrate Boyle's Law which governs the relationship between the pressure and volume of a gas. The data will be used to determine the mass of a text book.

1. 2-3 drops glycerine | 5. clamp/holder |

2. a laboratory syringe | 6. 4 or more text books |

3. septum to cover exit of syringe | 7. lab notebook |

4. ring stand | 8. safety gear |

Write your answers to these questions neatly on a separate piece of paper, showing all steps of all calculations. Be sure to do the calculations before the experiment and to re-write them if they aren’t neat and easy to read.

- What is the pressure in the syringe before any books are placed on the plunger? (Atmospheric pressure is usually slightly below 760 mmHg).
- Will the pressure in the syringe increase or decrease as each book is added?
- How will we be able to measure the pressure inside the syringe?
- What is the area of the top of the plunger? (Hint: You know the volume of the syringe in cm
^{3}and you can find the height between 0 mL and 30 mL; V_{cyl}= πr^{2}h). - The density of mercury (Hg) is 13.6 g/cm
^{3}. Say you have measured a pressure equal to a column of mercury that is 350 mm tall. Find the mass of the column of mercury if it has the same cross-sectional area as the plunger of your syringe.

- Use a few drops of glycerine the lubricate the plunger of the syringe
- Seal the tip of the syringe with the septum
- Set up the ring stand with the holder and clamp and put the syringe vertically in the clamp
- Seal the tip of the syringe with the septum
- Record the volume of air in the syringe without pressing down on the plunger at all
- Balance one textbook on the plunger of the syringe and gently press down on it, letting the plunger spring back up
- Record the volume of gas and the number of books and leave space for another value and an average in your data table
- Sequentially add more books in the same way and record the volume of gas and the number of books
- Once you have added the last book, remove them again one by one
- Record the volume next to the number of books as you remove each one; record the average of this value and the initial value you recorded; this will be the volume used in your calculations

According to Boyle’s Law, the volume of a gas is inversely proportional to its pressure. This can be written as an equation:

1 — = kP V

1 1 ——— = k(P_{a}+ nB) → ——— = kBn + kP_{a}V_{n}V_{n}

To find the mass of a book, find the value of B using the information above. This will be in units of pressure (mmHg) and you need units of mass. Use the model given in pre-lab question five to find the mass of the equivalent column of mercury. This mass is the same as the mass of the book. Check the result by finding the mass of the book using a balance.

Write a lab report on a separate piece of paper and be sure to create and include a neat, readable data table. For this lab you will also need the graph you made in class. Keep this lab for future reference. The lab report should include the usual sections. (See previous labs).