Lab Skills: Making Metric Measurements

Name:______Date:______Hr:______

Prelab Discussion:

In many biology investigations, precise measurements must be made before observations can be interpreted. For everyday measuring, we will use English units such as the inch, quart, and pound. For scientific work, and for everyday measuring in most countries, the International System of Units (SI) is used. Eventually, our country will use SI units for everday measuring as well. Like our money system, SI is a metric system. All units are based on the number 10. In the SI system, it is easy to change on unit to another because all units are related to one another by a power of 10. In this investigation, you will review SI units for measuring common objects within the classroom. You will also learn how to use some common laboratory equipment used for measuring.

Problem: How are metric units of measurement used in the laboratory?

Materials: Meter stick Coin (Nickel or Quarter) Metric Ruler Triple-beam balance 10 Pennies Small Test tube 50-ml beaker Unsharpened Pencil Rubber Stopper 100-ml graduated cylinder

Safety: Handle all glassware carefully. Note all safety procedures and report any questions, problems or accidents to the teacher.

Procedure:

Part A: Measuring Length 1. Use the meter stick to measure the length, width, and height of your laboratory table or desk (as assigned by teacher) in meters. Record your measurements to the nearest centimeter in Data Table 1. 2. Convert the measurements from meters to centimeters and then to millimeters. Record the conversions in Table 1. 3. Use a metric ruler to measure the length of a small test tube and the diameter of its mouth in centimeters. Record your measurements to the nearest millimeter in Table 1. 4. Convert the measurements from centimeters to millimeters. Record these conversions in Data Table 1. 5. Find the length of an unsharpened pencil (including the eraser) in millimeters. Record this measurement in Data Table 1. 6. Using the meter stick, measure your height in centimeters. Record your measurements in Data Table 1. 7. Convert your height measurements to meters and record the conversion in Data Table 1. 8. Use a metric ruler to measure the height of a stack of ten pennies, record your measurements in Data table 1. 9. Based on your measurement in step 8, record your estimations for the height of a stack of 100 and 1000 pennies respectively in Data table 1.

Part B: Measuring the Volume of a Liquid

1. Fill the test tube to the top with water. Pour the water into the graduated cylinder. 2. If the graduated cylinder is made of glass, the surface of the liquid will be slightly curved like the inside of a spoon. This is called the meniscus. To measure volume accurately you need to bend down so that your eye is level with the meniscus. You read the volume at the bottom of the meniscus. Perform this measurement and record the amount of water your test tube holds in Data Table 2.

Part C: Measuring Mass

Before beginning this portion of the investigation, be sure that the riders on the triple beam balance are moved all the way to the left and that the pointer rests on zero when nothing is on the measurement tray. See Figure below.

1. Place the 50 ml beaker (empty) on the measurement tray. Move the riders until the pointer balances at zero. Be patient, this may take several attempts and time for the beams to stop “bouncing”. Make all measurements to the nearest tenth of a gram. Record the mass of the beaker in Table 3. 2. Measure the mass of the rubber stopper and record in table 3. 3. Measure the mass of the coin and record in table 3. 4. Use the graduated cylinder to place exactly 40 ml of water in the beaker. Determine the combined mass of the beaker and the water. Record this mass in table 3. Data Tables:

Table 1: Measurements of Length Laboratory Table: Width: Length: Height: Meters Laboratory Table: Width: Length: Height: Cm Test Tube: Cm Length: Mouth: Test Tube: mm Length: Mouth: Pencil: Length: Your Height: CM Your Height: Meters Stack of 10 Height: Pennies: Stack of 100 Height: Pennies: Stack of 1,000 Height: Pennies:

Table 2: Measurements of Volume Volume of test tube:

Table 3: Measurements of Mass Mass of empty beaker: Mass of Rubber Stopper: Mass of Coin: Mass of Beaker plus water: Analysis and Conclusion Questions:

1. How do you convert meters to centimeters?

2. What is the largest volume of liquid your graduated cylinder can measure (accurately)?

3. What is the smallest volume of liquid your graduated cylinder can measure (accurately)?

4. What is the largest mass of an object your balance can measure?

5. What is the smallest mass of an object your balance can measure?

6. What is the mass of 40ml of water?

7. Which measurement is larger? (circle one from each option) a. 14mm or 1 cm b. 334 m or 1 km c. 1 m or 990 cm

Critical Thinking and Application:

1. Why is it easier to convert centimeters to meters instead of feet to miles?

2. How would you find the mass of a certain amount of water that was poured into a paper cup?

3. In this investigation, we found the mass of 40 ml of water, what is the mass of 1 ml of water?