Density Lab

Purpose: Learning the concept of density by measuring mass and volume. Finding which substance is the most dense by comparing different substances.

Background: The density of water is 1 g/mL. In order to find density, you must do mass divided by volume. You find solid volume by multiplying the length by width by height or by using displacement. You find mass by weighing the substance. In previous experiments, it is seen that alcohol dissolves faster than water.

Hypothesis: If the density of three substances is found, then the density from greatest to least of them will be: salt water, water, alcohol. This is because salt water is a mixture of 2 substances, which shows that there is more matter within the substance. Alcohol dissolves faster

than water, which shows that is less dense than water.

Independent Variable(s): The liquids/substances being measured.

Dependant Variable(s): The mass and density of the liquids.

Control(s): Volume of the liquids and all the equipment used.

Procedure:
1.

Take your data packet and pencil, then go to your lab station with a lab partner.

2. Take out a triple beam balance, graduated cylinder, long pipette, beaker, a wooden dowel, calculator and a centimeter ruler.

3. Find the mass(weight) of your graduated cylinder using the triple beam balance, and record it in your data packet. This will be the same for all liquids.

4. Go to the supply cart with the graduated cylinder and long pipette.

5. Fill up your graduated cylinder with 40 milliliters of alcohol using the long pipette, and record the volume in your data packet. This will be the same amount for all liquids.

6. Take your graduated cylinder and long pipette back to your lab station.

7. Find the mass(weight) of your graduated cylinder, now with the alcohol in it, using the triple beam balance, then record it in your data packet.

8. Subtract the mass of the graduated cylinder from the mass of the graduated cylinder and the alcohol to find the alcohol’s mass. Record it in your data packet.

9. Using your calculator, find the density of the alcohol by dividing the mass by the volume(40 mL). Record it in your data

packet.
10.

Drop a wooden dowel into your graduated cylinder. Wait for it to settle in the liquid, and measure the float height by measuring from the top of the liquid to the top of the dowel using a centimeter ruler. Record it in your data packet.

11. Clean out your graduated cylinder by dumping out your alcohol and rinsing it out in the sink.

12. Repeat steps 4 - 11 with salt water.

13. Fill your beaker with water from the sink.

14. Repeat steps 5-11 with water.

15. Make sure that your long pipette, beaker, dowel and graduated cylinder are all clean.

16. Put the triple beam balance, graduated cylinder, long pipette, beaker, a wooden dowel, calculator and a centimeter ruler away in their right spots.

17. Go back to your desk with your pencil and data packet.

Observations:

Alcohol

had a very strong smell(like a doctor’s office), liquid, felt wet, transparent

Water

no apparent smell, transparent, felt wet, liquid

Salt Water

smelled like the ocean, liquid, wet, slightly sticky, cloudy but not completely opaque

Data:

Data Table

The Density of Liquids

Liquid

Mass of Graduated Cylinder (g)

Mass of Graduated Cylinder + Liquid (g)

Mass of Liquid

(g)
Density (g/mL)
Float Height (cm)
Alcohol
95.9 g
127 g
31.1 g
0.78 g/mL
0.9 cm
Water
95.9 g
135 g
39.1 g
0.98 g/mL
1.6 cm
Salt Water
95.9 g
137.7 g
41.8 g
1.05 g/mL
1.8 cm

Analysis: The controls in this experiment were the volume of all three liquids and all of the equipment used. The independent variable was the type of liquids that were used, and the dependant variables were the mass and density of the types liquids. After finding the mass of all the liquids, it is shown that alcohol had the least amount of mass at 31.1 grams. Water was the next lightest at 39.1 grams, and the heaviest liquid was salt water at 41.8 grams. After calculating the density, it is shown that alcohol is the least dense at 0.78 g/mL. Water had a density of 0.98 g/mL, and salt water had a density of 1.05 g/mL. The density of the water was calculated wrong, as it was background knowledge that water has a density of 1 g/mL, not 0.98 g/mL. This could have happened by the inaccuracy of the triple beam balance, or an incorrect volume measurement Finally, the float height was measured. Alcohol was 0.9 cm, water was 1.6 cm, and salt water was 1.8 cm.

Conclusion: If the density of three substances is found, then the density from greatest to least of them will be: salt water, water, alcohol. This hypothesis is accepted because after completing the density experiments, it is plainly seen that the most dense liquid was salt water(1.05 g/mL), then water(0.98 g/mL), and finally alcohol(0.78 g/mL).