TEK I. 7A – investigate and identify properties of fluids

including

Density

Which box is more dense?

Both cubes have the same volume, but Cube 1 has more molecules so it is

denser than the Cube 2!

Density

Density compares the mass of an object to its volume

D = mass = g or g

volume mL cm3

Note: 1 mL = 1 cm3

Volume Displacement

A solid or liquid displaces a matching volume of water when the solid or liquid is placed in water.

33 mL

25 mL

Sample Problem

1. What is the density (g/mL) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?

(A) 0.2 g/ mL (B) 6.0 g/mL(C) 8.0 g/mL(D) 252 g/mL

33 33 mLmL25 mL25 mL

Density of Liquids

Liquids of lower density float on liquids of higher density.

Vegetable Oil

Density= .95 g/mL

Water

Density= 1.0 g/mL

Sample Problem

2. Which diagram represents the liquid layers in the cylinder?

(K) Karo syrup (1.4 g/mL),

(V) vegetable oil (0.91 g/mL),

(W) water (1.0 g/mL)

(A) (B) (C)

K

K

W

W

W

V

V

V

K

Solution

(A)

K

W

V(V) vegetable oil (0.91 g/mL), (W) water (1.0 g/mL),(K) Karo syrup (1.4 g/mL)

Sample Problem

3. If blood has a density of 1.05 g/mL at 96.7° F, how many milliliters of blood are donated if 575 g of blood are given?

(A) 548 mL

(B) 96.7 mL

(C) 1.25 mL

(D) 1.83 mL

Buoyancy

• Why does a boat float higher in saltwater than in freshwater?

A boat has more buoyancy in saltwater than in freshwater because saltwater is more dense than freshwater

Bouyancy

• Buoyancy is the tendency of a less dense substance to float in a more dense liquid.

How do life jackets increase your buoyancy?

• Lifejackets decrease your density by increasing your volume without increasing your mass much.

D= M V

Viscosity

• Have you ever been accused of moving “slower than molasses in January”?

• What makes a substance like molasses flow so slowly?

Molasses has a very high viscosity- which means it resists flow!

Viscosity

• Viscosity is resistance to fluid flow.

• When particles in a liquid are strongly

attracted there is high viscosity.

• When particles in a liquid are weakly

attracted there is low viscosity.

Viscosity

• What about when you heat up syrup? Then it seems to flow faster. What’s going on then?

•When you warm up a substance the kinetic energy of the molecules increase. This means that the molecules are moving faster, weakening the attraction between the particles, and lowering the viscosity.

4. During a laboratory investigation a student had to plan and implement an investigative procedure to determine the density of an unknown liquid. The student would need what equipment to do this investigation:

(A) test tubes, test tube rack, balance, beakers

(B) graduated cylinder, balance, beakers, funnel

(C) graduated cylinder, beakers, test tube rack, test tubes

(D) litmus paper, pH sensor, balance, Bunsen burner

5. A sample of an element has a volume of 78.0 mL and a density of 1.85 g/mL. What is the mass in grams of the sample?

144.30 g

6. A block of maple wood with a volume of 405 cubic centimeters and a density of 0.67 g/cm3 is sawed in half. The density of the two smaller blocks in now

(A) one-fourth the original density

(B) one-half the original density

(C) two times the original density

(D) the same as the original density

7. The picture shows the results of pouring a blue liquid into a clear liquid and allowing the mixture to settle for 25 minutes. Compared to the clear liquid, the blue liquid is more —A massive B denseC viscous D soluble

B

H

B

B

A

A