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## Measurement and Density, Chemistry tutorial

Measurement and Density:Purpose:Section 1: Through calculating the density of a recognized substance (water), find out the relative precision and precision of different glassware items.

Section 2: Find out the density of a salt water solution using the most precise and correct piece of glassware concluded in section 1

Equipment / materials:Weighing balance

Water

Unknown metal

cube

100 mL beaker

Unknown liquid

100 mL graduated cylinder

Metal cylinder

Introduction:The capability to build accurate and featured observations is vital in science. This chapter will focus on quantitative observations, more purposely, measurements. A measurement is described via a number and a scale or unit. The scale utilized is often changed. Due to convenience, the metric system is often utilized in many countries. The universal scale, though, utilized via scientists is the SI unit. In this chapter, we will focus on making accurate and detailed observations in measurements using the metric system while obeying the rules of significant figures.

In calculation to quantities described via a single unit, quantities can as well be described through a combination of units. One such instance is density. Density is simply one way to differentiate a material. Density (d) is described as mass (m) per unit volume (V). Therefore, units of both mass (for example g) and volume (for example mL) are needed in order to find out density.

D = m/V

Instances

1. A cube of copper was originated to contain a mass of 0.630 kg. What are the dimensions of the cube? (The density of copper is 8.94 g/cm

^{3}).Solution:

a) Find out the volume of the cube (note that kg have been converted to g):

8.94 g/cm

^{3}= 630 g / volume

volume = 70.47 cm

^{3}b) Each side of a cube is equivalent in length, so take cube root of the volume for length of cube side:

[cube root of] 70.47 cm3

= 4.13 cm

2. A cube of copper was originated to have a mass of 0.630 kg. What are the dimensions of the cube? (The density of copper is 8.94 g/cm3.)

Solution:

a) Find out the volume of the cube (note that kg have been converted to g):

8.94 g/cm

^{3}= 630 g / volumevolume = 70.47 cm

^{3 }b) Each side of a cube is equivalent in length, so take cube root of the volume for length of cube side:

[Cube root of] 70.47 cm

^{3}= 4.13 cm.3. A graduated cylinder is filled to the 40.00 mL mark by mineral oil. The masses of the cylinder previous to and after the computation of mineral oil are 124.966g and 159.446g. In a divide experiment, a metal ball bearing of mass 18.713 g is situated in the cylinder and the cylinder is once more sealed to the 40.00 mL mark by the mineral oil. The joined mass of the ball bearing and mineral oil is 50.952 g. Compute the density of the ball bearing.

Solution:

a) Determine the density of the mineral oil:

159.446 g minus 124.966 g = 34.480 g

34.480 g / 40.00 mL = 0.8620 g/mL

b) Determine the volume of the ball bearing:

50.952 g minus 18.713 = 32.239 g (this is the mass of mineral oil)

32.239 g divided by 0.8620 g/mL = 37.40 mL (this is the volume of mineral oil)

40.00 mL - 37.40 mL = 2.60 mL

c) The density of the ball bearing is 7.197 g/mL. This came from 18.713 g divided by 2.60 mL.

EXPERIMENT - Measurement and DensityPart A: Density of Liquidsi) Density of Water:

ii) Density of an Unknown Liquid:

Start through another dry graduated cylinder and do again the mass and volume measurements (above steps 1-7) via an unknown liquid (A, B or C assigned by the instructor). Calculate the density of the liquid, identify it (after discussing with the instructor), and compute the % error.

Part B: Density of Solidsi) Density of an unknown metal cylinder:

We will see the level of the water inside the graduated cylinder has risen. Evidence the new volume now (important figures once more). The variation in the volume levels provides us the volume of the metal cylinder

Now compute the density of the metal from volume using 2 different techniques.

ii) Density of an unknown metal cube:

DATA and CALCULATIONS:

Part A: Density of liquids

(i) Density of water:

Temperature of water: _____________

Mass of empty graduated cylinder: _____

Trial 1

Trial 2

Trial 3

Volume of water (mL)

Mass of water +

graduated

cylinder (g)

Mass of water alone (g)

Density of water

(g/mL)

Density from literature

% error

(ii) Density of unknown liquid: _____ (A/B/C)

Temperature of liquid: _____________

Mass of empty graduated cylinder: _________

Trial 1

Trial 2

Trial 3

Volume of liquid(mL)

Mass of liquid+

graduated

cylinder (g)

Mass of liquid alone (g)

Density of liquid

(g/mL)

Density from literature

% error

Part B: Density of solids

Density of unknown metal cylinder #: ___

Density from diameter and height measurement:

Mass of

metal

cylinder

(g)

Diameter

(cm)

Height

(cm)

Volume =

_____(cm3)

Density

of

metal

(g/cm3)

Density

from

literature

(g/cm3)

%

error

i) Density from volume displacement:

Volume of

water before

dropping metal

cylinder (mL)

Volume of water

after immersing

the metal

cylinder (mL)

Volume of

metal

cylinder

(mL)

Density of

metal

(g/cm3)

%

error

ii) Density of unknown metal cube #: ___

Mass

of

meta

l

cube

(g)

Dept

h

(cm)

Heigh

t (cm)

Widt

h

(cm)

Volume =

_____(cm3

)

Density

of

metal

(g/cm

^{3})Density

from

literature

(g/cm

^{3})%

Error

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