Science 8 Unit AMix & Flow of Matter

Goals of this Unit:• Identify WHMIS and HHPS symbols

• Describe safety precautions for using substances

• Identify examples of fluids in products and devices

• Describe examples of fluids used to transport, process, or use materials

• Identify important properties of fluids

• Distinguish between pure substances and mixtures

Goals (Continued)• Define concentration and solubility• Identify factors that affect solubility

and rate of dissolving• Describe the particle model of matter• Relate the behaviour of mixtures to

the particle model of matter• Define viscosity and describe how

temperature affects it• Calculate and compare densities• Relate density to the particle model

of matter

Goals (Continued)• Describe methods for altering the

density of fluids

• Explain buoyancy

• Describe pressure and examples of its use

• Compare the compressibility of liquids and gases

• Describe examples of technologies based on solubility

Goals (Continued)• Describe examples of technologies

based on the flow rates of moving liquids

• Explain how to design and construct a working model of a fluid-using device

1.1 – WHMIS Symbols and Safety Procedures

• Take a look at Figure 1.1 on page 9

• What are some unsafe lab practices that are taking place?

WHMIS• WHMIS is an acronym that

represents:

• W

• H

• M

• I

• S

WHMIS Symbols

HHPS• WHMIS is used in workplaces

• However, you may have noticed that many products that you have at home have a different set of symbols

• These symbols are known as HHPS

• H

• H

• P

• S

HHPS Symbols

Level of Hazard

Safety in the Lab• Safety is always our first concern when

we carry out any activity• Before starting any activity, be prepared

to:

1. Follow safety procedures outlined by the teacher and the text

2. Keep your eyes open for possible hazards, and report them immediately

3. Show respect and concern for your own safety and the safety of your clasmates and teacher

1.2 – The Many Uses of Fluids• Fluid:

• Some examples of fluids are:

Uses of Fluids• Slurries:

• Manufacturing Solids:

• Holding Other Substances:

Useful Properties of Fluids• Fluids have a number of important

properties• These properties are:1. Viscosity

2. Density

3. Buoyancy

4. Compressibility

2.1 – Pure Substances and Mixtures

• All matter can be classified as either pure substances or mixtures

• Pure Substance:

• Mixture:

Mechanical Mixtures and Solutions• Mixtures can be classified as either

mechanical mixtures or solutions

• Mechanical Mixtures

• Solutions

Suspensions and Colloids• Cloudy mixtures can be classified as

suspensions or colloids

• Suspensions

• Colloids

Matter Classification Chart

Matter

MixturesPure

Substances

Mechanical Mixtures

SolutionsSuspensions

& ColloidsCompounds Elements

Classifying SubstancesFluid Pure

SubstanceSolution

Soda Pop

Hot Chocolate

Distilled Water

Apple Juice

Windshield Washer Fluid

More Classifying of SubstancesSubstance Type of Matter

Baking Soda

Muddy Water

Chocolate Chip Cookie Dough

Gold (14 K)

Gold (24 K)

Whipped Cream

Paper Chromatography• Paper chromatography can be used

to test whether or not a fluid is a pure substance or a solution

• In this technique, a piece of filter paper is placed in a container with the fluid

• If the fluid is a pure substance, the solvent will carry that substance to a single level

• However, if the fluid is a solution, the substances will separate and move at different rates

• For instance, this black ink is a solution of three different inks

How Does it Work?• The substances in the solution are

attracted with different strengths to the paper

• The substances that are most strongly attracted to the paper do not move very far, but those that have the weakest attraction move the farthest

Applications of Chromatography• Chromatography, in many different

forms, can be used in a number of different fields, such as:

• Forensics

• Analytical chemistry

• Food analysis

• Environmental sciences

• Biological research

• Medical research

2.2 – Concentration and Solubility• Solutions consist of two parts: a

solute and a solvent

• Solute

• Solvent

Measuring Concentration• The concentration of a solution

describes the amount of solute in a given amount of solvent

• Concentrations can be described in a number of ways:

1. grams / 100 mL

2. percent (by volume or weight)

3. parts per million (ppm) or parts per billion (ppb)

4. moles per litre (used in chemistry)

Comparing Concentrations• A student dissolves 10 g of salt in 50

mL of water. Another student dissolves 25 g of salt in 100 mL of water. Which is more concentrated? How can you tell?

Saturated and Unsaturated Solutions

• All solutions have a given solubility at a certain temperature

• Solubility

• The solubility of a substance at a certain temperature defines its saturation point

• Therefore, solutions can be defined as saturated or unsaturated

• Saturated

• Unsaturated

The Solubility of Common Substances

Solubility in g / 100 mL of Water at 0oC

Compound Solubility

Salt 35.7

Baking soda 6.9

Carbon dioxide 0.35

Sugar 180

Hydrogen 0.00019

Oxygen 0.007

Ammonia 92

2.3 – Factors Affecting Solubility• Solubility depends on at least three

factors:

1. Type of solute

2. Type of solvent

3. Temperature

Type of Solute and Solvent• Solutes and solvents are often

classified as polar or non-polar based on their chemical structure

• Similar molecules (for example, a polar solute and solvent) will have high solubility

• This explains why some paints and dyes can be removed with water while others require a different solvent

Temperature• For most common solid or liquid

substances, solubility increases as temperature increases

• However, for gases, the reverse is true – the higher the temperature, the lower the solubility

Thermal Pollution• This means that thermal pollution

(warm waste water) from power plants and industries that enters lakes and streams reduces the amount of oxygen that can remain dissolved in the water

• As a result, many organisms can die or be forced to migrate to other areas if the water becomes too warm

2.4 – The Particle Model of Matter and the Behaviour of Mixtures

• The particle model of matter helps to explain a number of properties of various substances

• This model consists of four main points:

1 – All Matter is Made up of Tiny Particles

2 – The Tiny Particles of Matter are Always Moving

3 – The Particles in Matter may be Attracted or Bonded to Each Other

4 – The Particles Have Spaces Between Them

The Particle Model and Mixing of Substances

• When two substances are mixed, the particles of the solute fill in the spaces between the particles of the solvent

• This sometimes means that the total volume after mixing two substances is less than the sum volume of the substances before they are mixed

• The particle model also explains why substances dissolve

• The particles in the solute are attracted to the solvent particles

• Therefore, the solvent “pulls apart” the solute, causing it to dissolve

Factors Affecting Rate of Dissolving

1. Temperature

2. Size of Pieces

3. Stirring

3.1 – Viscosity and the Effects of Temperature

• All fluids flow, but some flow more quickly than others

• This is due to a fluid’s viscosity

• Viscosity

What Determines Viscosity?• Viscosity is due to the internal

friction between the molecules in a fluid

• Therefore, high viscosity fluids have a large amount of internal friction

Temperature and Viscosity• As the temperature of a fluid

increases, its viscosity decreases

• The particle model of matter can explain this:

Measuring Viscosity• The ramp method involves pouring a

fluid down a ramp and timing how long it takes for the fluid to reach the bottom

• The slower the time, the greater the viscosity of the fluid

• This can also be used to confirm the effect that temperature has on viscosity

3.2 – Density of Fluids• Density

• Not all substances have the same density

• This is because they are made of different types of matter

What happens when people misunderstand density…

Calculating Density• Density is calculated using the

following formula:

• Density = mass ÷ volume

• The most common units for density are g/mL and kg/L for fluids and g/cm3 for solids

Example• Joe uses a beaker that has a mass of

75.0 g in a density experiment. He puts 120 mL (or 120 cm3) of sand into the beaker. The mass of the sand and beaker is 270 g. What is the density of the sand?

Comparing Density on Graphs• On the graph, which substancea) Has the greatest denistyb) Has the least densityc) Has a density of about 1.0 g/mL

Densities of Unknown Substances

0

20

40

60

80

100

120

140

160

10 20 30 40 50 60

Volume (mL)

Mas

s (g

) Substance A

Substance B

Substance C

3.3 – Density, Temperature, and Buoyancy

•Density can change with temperature•This can be explained using the particle model of matter

Solid Liquid Gas

But What About Water?• Water becomes less dense as it

becomes a solid

• This is because the water molecules arrange themselves in a specific shape that has large amounts of empty space

• As a result, water expands and becomes less dense when it freezes

Changing Density by Changing Concentration

•If we add a solute to a solvent, the density of the solution will change•This is because there are more particles in a given volume, which means the solution is more dense

Distilled Water (1 g/mL) Salt Water (1.02 g/mL)

Buoyancy• Buoyancy

• Buoyancy depends on two forces:

Positive, Negative and Neutral Buoyancy

Positive Buoyancy

Negative Buoyancy

Neutral Buoyancy

Applications of Buoyancy• Several transportation

technologies rely on buoyancy

• Cargo ships have markings known as a Plimsoll Line painted on their hulls

• This line shows how heavily the ship can be loaded for various weather conditions

Balloons and Blimps• Both balloons and blimps rely on

buoyancy to stay in the air• Hot air balloons heat air and trap it,

creating a low-density pocket of air that floats in the cooler air around it

• Blimps use a number of gases that are less dense than air (mostly helium) to float

The Hindenburg Disaster (1937)

3.4 – Compression of Fluids• Compressibility

• However there are differences in the compressibility of different fluids

Comparing Compressibility of Liquids and Gases

•Gases are much easier to compress than liquids•This can be explained through the particle model of matter

Liquid Gas

3.5 – Pressure in Fluids – Pascal’s Law

• Pressure

• Pressure is measured in pascals (Pa), or occasionally in N/cm2

• Ex: A force of 350 N is exerted over an area of 2.0 m. What is the pressure produced?

Blaise Pascal• Blaise Pascal was a

French mathematician who studied how pressure affects a fluid

• He investigated both the relationship between pressure and depth, and the affect of applying force to a fluid in a closed container

Pressure and Depth• Pascal determined that as the depth

of a fluid increased, the pressure also increased

• Reason:

Pascal’s Law• Pascal studied how forces affect

fluids in a closed system

• He developed Pascal’s Law:

Applying Pascal’s Law – Hydraulic Systems

• A hydraulic system is a fluid placed in an enclosed system that is made up of two pistons and a connecting tube

• When force is placed on one piston, it transmits the force through the fluid (in all directions) and forces the other piston to move

Advantages of Hydraulic Systems• Hydraulic systems allow us to

increase the force that is exerted on an object

• Therefore, we can use a small force to move or lift a very large object

Pneumatic Systems• Pneumatic systems are similar to

hydraulic system, but they use compressed air or gases instead of a liquid

• The compressed air moves parts within the system, which causes the device to operate

Maintaining Pressure• Pneumatic and hydraulic systems

must operate under pressure

• If a leak develops in the system, the entire system would fail

4.1 – Technologies Based on Solubility

• A number of technologies rely on solubility

• Most cleaners use the principle of solubility to operate

• Detergents have surfactants which attach themselves to oil and dirt particles and pull them off of fabrics and other materials

• These surfactants make the dirt and oil soluble in water

How do Surfactants Work?• Surfactants have one end that

attaches to water molecules and another end that attaches to oils

• This allows the normally insoluble oils to be dissolved in water

Diving and Decompression• At high water pressures, more

nitrogen gas dissolves in our blood than normal

• When a diver returns to the surface, this nitrogen gas leaves the blood

• However, if a diver returns too quickly, nitrogen bubbles suddenly form in the blood (similar to the bubbles that form when you open a bottle or can of pop)

The Bends• When these bubbles form, they

collect in the joints, causing severe pain

• As well, if bubbles occur in the brain, the diver can suffer a stroke or even die

• Treatment involves the use of a hyperbaric chamber

Hyperbaric Chamber• The hyperbaric chamber increases

the pressure on the diver’s body, allowing the nitrogen bubbles to re-dissolve

• By slowly releasing the pressure, the nitrogen can safely leave the diver’s blood

4.2 – Technologies Based on Flow Rates and Moving Fluids

• Often we need to move fluids from one place to another

• Both pumps and valves can be used to control where the fluid moves, and how quickly it moves

Pumps• Pump

• Pumps can be found in many devices:

How a Bicycle Pump Works•Within a bicycle pump is a piston•As the piston is pushed down, it compresses the air inside the cylinder•This compressed air is forced out of a valve and through the hose (to an area of lower pressure)

Pull Push

Pipeline Pigs• Pipeline pigs are computerized units

that are used to clean and analyze oil and gas pipelines

• These pigs are pushed though the pipelines by the pressure of the fluid within the pipeline

Valves• Valves

• Valves come in a number of different shapes and sizes

• Valves can even be found inside your body

Valve TypesBall Valve Butterfly

ValveSchrader

ValveScrew Valve

4.3 – Submarines• Many parts of the ocean are too deep

for humans to explore because of the pressure

• Therefore, we have developed submarines and bathyscaphs (such as the Trieste) to explore the deep sea

How do Submarines Work?• Submarines change their depth by

changing their density

• They do this through the use of ballast tanks

• As the submarine fills its ballast tanks with water, it becomes more dense than the surrounding water and sinks

• To rise, the ballast tanks are emptied of water and filled with air, which makes the submarine less dense than the water around it

Robot Submarines• Robot submersibles (such as the

Canadian ROPOS) can dive even deeper than manned submarines

• This is because there is no easily-crushed pocket of air at the center of the submersible

End of Unit