Chemistry/Measuring Mass

Science 8 Laboratory Investigation

MEASURING MASS

Procedure: 1. “Zero” your balance as demonstrated by your teacher. The steps are: (a) Move all the sliding weights to the left. (b) Be sure there is nothing on the balance pan except the stainless steel pan. (c) If the pointer at the end of the balance beam does not point to the centre of the scale, adjust the screw on the other end of the balance beam. 2. Find the mass of each object in the table below. You should find the mass to the nearest 0.01 g. Your teacher will give you instructions about filling the graduate cylinders with water. Object Mass (g) (a) One penny (b) One nickel (c) One dime (d) One quarter (e) One dropping pipet i) our data ii) data from ________________________________ iii) data from ________________________________ (f) A group of 10 dropping pipets i) our data ii) data from ________________________________ iii) data from ________________________________ (g) Mass of 25 mL graduated cylinder (h) Mass of 25 mL graduated cylinder + 25 mL of water (i) Mass of 10 mL graduated cylinder (j) Mass of 10 mL graduated cylinder + 10 mL of water

QUESTIONS
1. Which of the coins you weighed has a mass that is closest to a whole number?

2. You collected data for three different groups of 10 pipets in part (f) of your data table. For each of the three masses in part (f), divide the total mass of 10 pipets by 10 to find the average mass of one pipet. Show your work.

3. Look at the average masses you calculated in question 1, and look at the three masses you recorded in part (e) of your data table. Which set of three masses is most similar to each other: the set of three masses recorded in part (e) or the set of three average masses calculated in question 1? Explain your answer.

4. A student weighs a handful of pipets and find they have a mass of 40.12 g. The average masses you calculated in question 1 give you a good guess for the mass of any randomly-selected pipet. Based on any one of the average masses you calculated in question 1, how many pipets did the student have in the handful? Show how you arrived at your answer. You may have to round off your answer slightly because an whole number of pipets was taken.

5. Calculate the mass of 25 mL of water by subtracting the mass of the empty 25 mL graduated cylinder from the mass of the 25 mL graduated cylinder when it contains 25 mL of water.

6. Calculate the mass of 1 mL of water by dividing the mass of 25 mL of water by 25.

7. Calculate the mass of 10 mL of water by subtracting the mass of the empty 10 mL graduated cylinder from the mass of the 10 mL graduated cylinder when it contains 10 mL of water.

8. Calculate the mass of 1 mL of water by dividing the mass of 10 mL of water by 10.

9. Do you think the mass of 1 mL of water you calculated in question 5 is close to the mass of 1 mL of water you calculated in question 7. Explain your answer.