Nmidne

Laboratory # 1

Theme: Laboratory Procedure Procedure: 1. Inserting glass tubing into rubber stopper can be very dangerous. The following precautions should be observed to prevent injuries: a)Never attempt to insert glass tubing that has a jagged end. All glass tubing should be fire polisher before it is inserted into a rubber stopper. b) Use water or glycerin as a lubricant on the end of theglass tubing before inserting it into a rubber stopper. c)Wear leather glove or place folded cloth pads between your hands and the glass tubing. Hold the glass tubing as close as possible to the part where it is to enter the rubber stopper. Always point the glass tubing away from the palm of your hand that holds the stopper. Using a twisting motion, gently push the tubing into the stopper hole.d)At the end of the experiment, put on leather gloves or place folded cloth pads between your hand and the glass tubing and remove the rubber stoppers from the tubing to keep them from sticking or freezing to the glass. Use a lubricant as directed in step 1b if the stopper or tubing won t budge. 2. When inserting glass tubing into the rubber or plastic hose, observe the same precaution discuss instep 1a-1c. The glass tubing should be lubricated before insertion into the rubber or plastic hose. The rubber hose should be cut at an angle before the insertion of the glass tubing. The angled cut in the hose allow the rubber to stretch more readily. At the end of an experiment, immediately remove the glass tubing from the hose. When disassembling, follow the precautions that were given in step 1d.Carefully follow these precautions and techniques whenever an experiment requires that you insert glass tubing into either a rubber stopper or a rubber or plastic hose. You will be referred to these safety precautions throughout the lab course.

Handling solids, procedure 1. Solids are usually kept wide-mouthed bottles. A spatula should be used to dip out the solid. Using a spatula remove aquantity of sodium chloride from its reagent bottle. In order to transfer the sodium chloride to a test tube, first place it on a piece of glazed paper about 10cm square. Roll the paper into a cylinder and slide it into a test tube that is lying flat on the table. When you lift

the tube to a vertical position and tap paper gently, the solid will slide down into the test tube. 2. Dispose on thesolid sodium chloride and glazed paper in the waste jar or containers provided by your teacher.

The balance, procedure 1. When a balance is required for determining mass, you will use a gram balance. 2. Before using the balance, always check to see if the pointer is resting at zero. If the pointer is not at zero, check the riders on the scales. If all the scale riders are at zero, turn the zeroadjust knob until the pointer rests at the zero. The zero adjust knob is usually located at the far left end of the balance beam. 3. In many experiments you will be asked to determine the mass of a specified amount of a chemical solid. Use the following procedure to obtain approximately 13g of sodium chloride. a)Make sure the pointer on the balance is set at zero. Obtain plastic cup of weighing andplace on the balance pan. Determine the mass of the plastic cup by adjusting the riders on the various scales. Record the mass of the plastic cup weighing. b)Add 13g to the balance by sliding the rider on the 100g scale to 10 and the rider on the 10g scale to 3. c)Using a spatula, obtain a quantity of sodium chloride from the reagent bottle and place it on a separate piece of glazed paper. d)Nowslowly pour the sodium chloride from the glazed paper onto the plastic cup weighing on the balance pan, until the pointer once again come to zero. In most case, you will only have to be close to the specified mass. Record your exact mass of sodium chloride and plastic cup weighing. Remember to substract the mass of the plastic cup weighing to find the mass of the sodium chloride. 4. Wash your...