Presentation on theme: "Reading Graduated Cylinders Important Stuff!. Graduated cylinders are used to measure the volume of liquid samples and are available in many different."— Presentation transcript:
Reading Graduated Cylinders Important Stuff!
Graduated cylinders are used to measure the volume of liquid samples and are available in many different sizes.
Reading the Volume from a Graduated Cylinder Determine the gradation markings on the GC. Determine the volume contained in a graduated cylinder by reading the bottom of the meniscus at eye level. Read the volume using all certain digits and one uncertain digit. – Certain digits are determined from the calibration marks on the cylinder. – The uncertain digit (the last digit of the reading) is estimated.
Depending on the size of the graduated cylinder and the graduations, the uncertain digit may be to the milliliter ( 1X ), the tenth of a milliliter ( 1.X ), or the hundredth of a milimeter ( 1.1X ). You will have to look at the graduated cylinder to determine how many digits to record!
Steps in brief… Step 1: Determine the scale increment: – To find the scale increment, subtract the values of any two adjacent labeled graduations and divide by the number of intervals between them Step 2: Use the graduations to find all certain digits: – Use the labeled graduations and the scale increment to find the certain digits in the measurement. Step 3: Estimate the uncertain digit and obtain a reading: – Estimate the distance that the meniscus lies between the two graduations as a decimal fraction and multiply by the scale increment
Looking at a 10 mL cylinder What is the volume you should record for the solution in the image to the right? – 6.31 mL correct – 6.3 incorrect – WHY?
Looking at a 25 mL cylinder What is the volume you should record for the solution in the image to the right? – 21.50 mL correct – 21.5 incorrect – Why?
Looking at a 100 mL cylinder What is the volume you should record for the solution in the image to the right? – 52.8 mL correct – 53 mL incorrect – Why?