Grade 8 - Mix and Flow of Matter
Section 1: Matter on the Move
Matter is anything that has mass and volume (occupies space). The amount of matter in an object is called Mass. Mass can be measured in milligrams (mg), grams (g) or kilograms (kg). An object's mass remains the same. Weight is a measure of the pull of gravity on an object. Therefore the weight of an object changes depending on the gravity. You would weigh less on the moon than you would weigh on Earth because the moon has less gravitational pull.
The Particle Model of Matter is a scientific description of the tiny particles that make up all things. The key elements in this model include:
- All substances are made of tiny particles
- All particles in a pure substance are the same.
- Different pure substances are made of different particles
- All the particles have spaces between them
- All the particles are always in motion. As described prescribed, the speed of the particles increases when the temperature increases, and vice versa.)
- The particles in a substance are attracted to one another. The strength of the attraction depends on the type of particle.
States of Matter
Matter can be found in three common states namely: solids, liquids and gases.
Solids: Solids have a shape and take up a fixed amount of space. In solids, the particles of matter are packed tightly and mostly in a regular pattern and cannot be easily compressed. The particles form a pile when they are poured; (they do not continue to flow apart from each other). The pencil, pen, book, desk, blocks, wood, ice ... are all solids.
Liquids: Liquids do not have a fixed shape, they take the shape of the container. In liquids, the particles that make up matter are farther apart, there is little free space between particles. They are not easily compressible. Liquids can be poured and will always flow to the lowest possible level of the container and form a flat surface at rest. Water, juice, milk, and oil are examples of liquids.
Gases: If you pour juice into a glass, it goes to the bottom of the glass makes the glass half full. Gases do not have a fixed shape. If poured, gases spreads out throughout the container and do not flow to the lowest possible level. In gases, the particles spread out so as to fill the space in the container. If the space is small, the particles will be tight together, if the space is big, the particles will be spread out farther apart. Air is mostly made out of gases.
Changes of State: A change of state occurs when the particles of a substance gain or lose energy. Because this change is due to kinetic energy, the change of state is a physical process, which is reversible, and no matter how much kinetic energy is put into or taken away from the material, the material will always stay the same and its mass will also remain the same.
The most common form of matter in our universe exists in a fluid state called plasma, which is a gaslike mixture of positively and negatively charged particles. It is often considered to be the fourth state of matter.
Section 2: Mixing and Dissolving
All substances are either pure or mixtures. Pure substances can either be elements or compounds. Pure substances have unique set of properties, or characteristics that remain consistent. Mixtures can either be homogenous or heterogenous based on the interactions between the elements in the mixture.
Element
An element is a pure substance with its own set of physical and chemical properties that cannot be broken down into simpler chemical substances. It has only one type of atom present.
Compound
A compund is a pure substance that can be broken down by a chemical change into two or more elements. Compounds have more than one type of elements that are chemically combined.
Mixtures are two or more substances that are NOT chemically combined. They do not have constant characteristics such as boiling or melting points. The components retain their characteristic properties. They may be separated into pure substances by physical methods. Mixtures of different compositions may have widely different properties.
Homogenous Mixtures
These are mixtures which look as though they have only one set of properties. The blended mixture has equal amounts of both substances (all parts of the mixture are the same). If the homogenous mixture does not have any settling of any of the substances it is made of, then it is called a solution. Solutions occur because each particle interacts with other particles and the resultant particles are evenly distributed throughout the entire mixture.
In solutions, the substance in the smallest amount and the one that dissolves or disperses is called the SOLUTE. The substance in the larger amount is called the SOLVENT. water is commonly called the universal solvent. The gases, liquids, or solids dissolved in water are the solutes.
Heterogenous Mixtures
In a heterogenous mixture, the properties of the pure substances, can still be observed. If you notice there are two or more materials that are visible within a mixture, then it is a heterogeneous mixture.
In-Between Mixtures
There are several mixtures that cannot be classified simply as homogenous or heterogenous.
If you observe a mixture in which the particles settle slowly after mixing, this type of mixture is called a suspension (Such as orange juice.)
A heterogeneous mixture, in which the particles do not settle at all, is called a colloid (eg. milk, fog, smog etc.) Colloids are solutions. They can be described as a substance trapped inside another substance. They can be identified by their characteristic scattering of light. For example: air trapped inside the fat molecules in whipped cream. The particles in colloids are smaller than a suspension but larger than molecules.
Mixtures that are obviously/visibly two or more substances are called mechanical mixtures. The separate parts of the mechanical mixture are called phases.
An emulsion is a mixture of two or more liquids that are normally immiscible owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. An emulsifier is a substance that stabilizes an emulsion by reducing the oil-water interface tension. Emulsifiers are a part of a broader group of compounds known as surfactants. Some examples of emulsions include homogenized milk, mayonnaise, butter etc.
Mixing and Dissolving
Some substances pull apart into individual molecules when placed in other substances. The dissolving substance is the SOLUTE. The substance doing the dissolving is the SOLVENT. The particles spread apart equally throughout the solvent to create a SOLUTION. Increasing the temperature will increase the solubility, more can dissolve. Is expressed as a concentration. Mass of solute/mass of solvent at a certain temperature.
Water - The Universal Solvent
97% of the water on Earth is Ocean water, 2% is frozen and only about 0.5% is 'usable'. Water is called a 'universal solvent' because it can dissolve so many materials.
The Rate of Dissolving
The rate at which a solute dissolves in a solvent is called the rate of dissolving and is influenced by:
Agitation (such as shaking, stirring etc.)
Temperature
Pressure
There is a limit to the amount of solute that can dissolve in a solvent. A saturated solution is one in which no more solute will dissolve in a specific amount of solvent at a specific temperature. An unsaturated solution is one in which more solute can be dissolved in a specific solvent at the same specific temperature.
Solubility Curves for Solids. The amount of solid which dissolves in water at a particular temperature is different for different substances. The next graph shows the solubility curves for potassium nitrate and sodium chloride. The temperature range shown is approximately 0 to 70°C. There is very little change in the amount of sodium chloride which dissolves over this temperature range but a very big change in the amount of potassium nitrate which dissolves.
The solubility curve for gases is the opposite of the solubility curve for solids. The solubility of a gas decreases as the temperature increases. The graph below shows the solubility curve for oxygen gas. The temperature range shown is approximately 0 to 50°C.
Saturation can be explained using the particle theory. In this case, the attractive forces between the particles becomes balanced and no more particles of the solute can be attracted by the particles of the solvent.
A solution that contains more solute than would normally dissolve at a certain temperature is called a super-saturated solution.
Some solvents are used for special circumstances because they will dissolve some solutes that water and other solvents cannot. For example, rubbing alcohol is use to dissolve chlorophyll (grass stains) from clothes. Perchloroethethylene is the solvent used in 'dry' cleaning, even though it is a liquid.
Section 3: Separating Mixtures
Solid particles can be removed from a mixture by filtration. The success of this technique depends on the pore size of the filter medium. Particles smaller than the pores will cross and form part of the filtrate.
Solvents can be removed by distillation and crystallization. Distillation is a separation method that allows all the liquid fractions of a mixture to be separated from each other and collected independently.
Purification of salt water (Desalination) can be done through distillation where the water boils at 100 C, leaving the salt behind to crystallize, the water can now be condensed and drunk.
Desalination can also be achieved through evaporation. The concept is similar to distillation but can be applied under different conditions.
Fractional distillation
Is the process used to separate the mixture of hydrocarbons in petroluem products. When the petroleum is heated, it changes into a gas (vaporize), which is collected and cooled, enabling it to change back into a liquid. The different components of the mixture condense at different temperatures therefore they recondense in separate fractional parts. Fractional products can then be further processed into over 500,000 types of petrochemicals.
Section 4: Particle Theory
Particle theory refers to the idea that all matter is composed of tiny, indivisible particles. Depending on the substance itself, these particles can be atoms, molecules, or subatomic particles such as protons, neutrons, and electrons. The concept of particle theory helps explain the behavior and properties of matter at the microscopic level.
Particle theory is a fundamental concept in chemistry and physics, providing a framework for understanding the properties and behavior of matter at the microscopic level. It has been instrumental in advancing our understanding of various phenomena, including phase changes, chemical reactions, and the behavior of gases.
Let us review some of the concepts in the particle theory:
Particles are always in motion, and the kinetic energy of their movement increases with temperature. This motion is responsible for the macroscopic properties of matter, such as its state (solid, liquid, or gas) and its ability to conduct heat.
There is empty space between particles, even though matter may appear solid. This is why substances can be compressed or expanded.
There are attractive forces between particles, which vary depending on the type of particles and the state of matter. For example, solids have strong forces of attraction, liquids have weaker forces, and gases have very weak forces.
The arrangement and motion of particles determine the state of matter. In a solid, particles are closely packed and vibrate in fixed positions. In a liquid, particles are still closely packed but can move past each other. In a gas, particles are more spread out and move freely.
Viscosity
Viscosity is a property of fluids (liquids and gases) that quantifies their internal resistance to flow. It arises from the interaction between the molecules of the fluid as they move past each other. Understanding viscosity is important in designing processes, optimizing fluid flow in pipelines, developing products, and ensuring the proper functioning of various systems in different industries.
Factors Influencing Viscosity:
Temperature: Generally, viscosity decreases with an increase in temperature for liquids and increases for gases.
Composition: The type and size of molecules in a fluid influence its viscosity. Larger and more complex molecules often result in higher viscosity.
Viscosity in Liquids:
High Viscosity: Substances like honey and molasses have high viscosity, meaning they flow slowly.
Low Viscosity: Water and most common liquids have lower viscosity and flow more easily.
Measuring Viscosity
Flow rate is a measure of a liquid's viscosity. The flow rate of a fluid is measured in ml/s (milliliters per second). By measuring the flow rate, we are able to compare the viscosity of different fluids because the thicker the fluid, the slower it flows and the more viscous it is.
Changing Viscosity
As previously mentioned, temperature affects the viscosity of a fluid. Increasing the temperature of a fluid will lower its viscosity. Lowering the temperature of a fluid will increase its viscosity.
Practical Applications
The principles of aerodynamics, drag and turbulence are associated with the concept of viscosity. Examine why these principles are related to how thick a fluid is.
Motor Oil is used as a lubricant in engines at different temperatures in different regions and in different seasons of the year.
Cooking requires knowledge of the effects that temperature has on viscosity. Which explains why sauces get thicker as they cool.
Section 5: Density and Bouyancy
Density is a physical property of matter that measures how much mass is contained in a given volume. It is often expressed as mass per unit volume and is a fundamental concept in physics and chemistry.
Density = mass/volume
The units for density depend on the units used for mass and volume. Common units include kilograms per cubic meter (kg/m³) in the metric system and grams per cubic centimeter (g/cm3) or kilograms per liter (kg/L) in other systems.
As mass increases while volume remains constant, density increases. As volume increases while mass remains constant, density decreases.
Measurement of Density
As the formula above, you can calculate the density of an object if you know its mass and volume. The mass can be measured using a balance.
The method to estimate the objects volume depends on whether the object is regularly shaped or irregular. The volume of a regularly shaped is obtained by measuring its legnth, Witdh and Height where Volume = L*W*H.
One way to determine the volume of an irregular object is to measure its mass in air and then in water, subtract the second measurement from the first, and divide by the density of water.
Another way to determine the volume of an irregularly shaped object is to submerge the object in a full container of water. The volume of the object equals the volume of water that overflows, (ie. that it displaces)
To determine the volume of an object that floats, first attach a metal sinker to the object. Next, submerge the metal sinker and measure the over-flow. Then submerge the object and measure the total overflow. The volume of the object equals the difference between the measurements.
The density of water is often used as a reference point. Water has a density of 1 g/cm³ or 1000 kg/m³ at standard conditions.
Density can be affected by temperature and pressure changes. For gases, an increase in temperature often leads to a decrease in density, while an increase in pressure typically increases density.
Hydrometers:
A hydrometer is a device that uses buoyancy to measure density directly. Hydrometers are calibrated in g/ml, by making marks that indicate the levels at which the instrument floats in different fluids. The higher the hydrometer floats, the higher the density of the liquid.
Density is often used to identify substances. Each material has a characteristic density, allowing scientists to determine the composition of unknown substances. Buoyancy: The principle of buoyancy is related to density. Objects float or sink in a fluid depending on their density compared to the density of the fluid.
Archimedes' principle
Archimedes' principle is a fundamental concept in fluid mechanics, named after the ancient Greek mathematician and inventor Archimedes. The principle states that when a body is partially or wholly submerged in a fluid (liquid or gas), it experiences an upward buoyant force equal to the weight of the fluid it displaces. This buoyant force acts in the opposite direction to gravity.
Applications:
Archimedes' principle is fundamental to understanding the behavior of ships, submarines, and other floating vessels. It is also essential in the design of hot air balloons, which rely on the principle to generate lift.
Density and Displacement:
The principle is directly related to the density of the fluid and the volume of fluid displaced. Less dense objects will displace more fluid and experience greater buoyant force.
Archimedes' principle is a key concept in fluid mechanics and plays a crucial role in understanding the behavior of objects in fluids, leading to practical applications in various engineering and scientific fields.
Bouyancy
Buoyancy: The buoyant force acts in the upward direction and is responsible for the apparent loss of weight of an object when immersed in a fluid. The object will experience a net force equal to the difference between its weight and the buoyant force.
Floating and Sinking:
If the weight of the object is equal to the buoyant force, the object will remain suspended in the fluid but will not sink (neutral buoyancy). If the weight is greater, the object will sink. If the weight is less, the object will rise to the surface.
Section 6: Fluid Pressure
Pressure is the force experienced by an object divided by the area of the surface on which the force acts. The force is acting perpendicular to the surface.
Atmospheric pressure, describes the pressure exerted by the weight of the air above us. The air goes up a long way, so even though it has a low density it still exerts a lot of pressure. On every square meter at the Earth's surface, then, the atmosphere exerts about 1.0 x 105 N of force. This is very large, but it is not usually noticed because there is generally air both inside and outside of things, so the forces applied by the atmosphere on each side of an object balance. It is when there are differences in pressure on two sides that atmospheric pressure becomes important.
Compressibility
The compressibility of a material is the ability to decrease the volume when pressure is applied. Gases are highly compressible. As pressure increases, the volume of the gas decreases. Liquids are nearly incompressible. As the pressure on the liquid increases, the volume remains unchanged.
Measuring Pressure
Pressure is measured by dividing the amount of force, by the area where the force is applied.
P = F / A
Where F is the force, and A is the area. 1 Pa = 1 N/m2
Other units include atmospheres (atm), millimeters of mercury (mmHg), and pounds per square inch (psi).
Barometers
A barometer is a scientific instrument used to measure atmospheric pressure. Atmospheric pressure, often referred to simply as "air pressure," is the force exerted by the atmosphere on a unit area and is an important parameter in weather forecasting. The barometer is a key tool for understanding changes in atmospheric pressure, which can indicate impending weather changes.
There are different types of barometers, but one of the most common is the mercury barometer, which was invented by Evangelista Torricelli in 1643. Here's how a mercury barometer works:
Principle of Operation:
The barometer is a sealed glass tube, typically about a meter in length, filled with mercury. The tube is closed at one end and open at the other end. The open end of the tube is inverted and submerged in a container of mercury. Atmospheric pressure exerts force on the surface of the mercury in the container, causing the mercury in the tube to rise or fall.
Mercury Column and Atmospheric Pressure:
The height of the mercury column in the tube is directly related to atmospheric pressure. As atmospheric pressure increases, the mercury column is pushed higher in the tube, and as atmospheric pressure decreases, the mercury column falls.
The atmospheric pressure is typically expressed in units of millimeters of mercury (mmHg) or inches of mercury (inHg). Standard atmospheric pressure at sea level is approximately 760 mmHg or 29.92 inHg.
Aneroid Barometer
Because mercury barometers are expensive and cumbersome, the aneroid (fluidless) barometer offers an alternative. The aneroid barometer is a spring balance, with a sealed, partially evacuated canister with flexible walls. A spring is inserted into the canister to keep the chamber from collapsing. Measurement of air pressure by an aneroid barometer involves balancing the weight of the atmosphere against a known spring force exerted upon the walls of the chamber. Increasing the outside air pressure collapses the walls of the canister slightly, because the pressure on the outside wall of the canister wall is greater than the pressure on the inner wall. While not as accurate as the mercury barometer, the aneroid barometer is more widely used because it is compact, portable, rugged, relatively cheap and it can be adapted to become a recording instrument, or a barograph.
Digital barometers are also common, providing a numerical readout of atmospheric pressure.
Section 7: Fluid Systems
Fluid systems are present in living things and several man-made devices. Living things rely on fluid systems to transport important biochemicals needed for the body, thermoregulation, nervus system responses etc.
Hydraulic Systems: Fluid pressure is used in hydraulic systems to transmit force over a distance. This is commonly employed in machinery, car brakes, and heavy equipment. Barometers and Manometers: Devices like barometers and manometers measure atmospheric pressure and pressure differences in fluids, respectively.
Because force equals pressure multiplied by area, forces can be increase (by enclosing a liquid between two movable pistons of different areas)
Mechanical advantage: Is used in such hydraulic actuators as automobile brakes and the control flaps of airplanes. Hydraulic presses, invented by British engineer Joseph Bramah in 1796, are used to shape, extrude, or stamp metals and to test materials under high pressures.
Effort Force Advantage: The force is equal to the pressure multiplied by the area, so where the surface area is small, the force exerted is small, where the surface larger, the force exerted is larger.
Valves & Pumps
Valves and pumps are essential components in fluid control systems, playing crucial roles in regulating the flow of liquids or gases in various industrial, commercial, and residential applications.
Valves:
Valves are devices designed to control the flow of fluids by opening, closing, or partially obstructing passages.
Types of Valves:
Gate Valve: Provides a straight-through flow path when fully open; commonly used in applications where a straight-line flow of fluid is needed.
Ball Valve: Uses a spherical closure element to control flow; provides quick on/off control without pressure drop.
Butterfly Valve: Uses a disc mounted on a rotating shaft to control flow; suitable for large-volume applications.
Check Valve: Allows flow in one direction only, preventing backflow.
Control Valve: Modulates the flow of fluid to control the process.
Valves are essential in many applications including:
Water and Gas Systems: Valves regulate the flow of water and gas in plumbing systems.
Oil and Gas Industry: Used in pipelines and refineries for flow control.
Manufacturing Processes: Control the flow of liquids or gases in industrial processes.
HVAC Systems: Regulate the flow of air and water in heating, ventilation, and air conditioning systems.
Pumps
Pumps are mechanical devices designed to move fluids (liquids or gases) from one place to another by creating a flow. Pumps are essential in:
Water Supply: Pumps are used to supply water for various purposes, from residential water wells to municipal water distribution systems.
Chemical Industry: Pumps handle the transfer of chemicals in manufacturing processes.
Oil and Gas Industry: Essential for transporting crude oil, natural gas, and refined products.
Wastewater Treatment: Pumps play a crucial role in moving wastewater through treatment processes.
Features of Pumps:
Head: The height to which a pump can raise a fluid.
Flow Rate: The volume of fluid moved per unit of time.
Efficiency: The ratio of the energy output to the energy input.
Types of Pumps
Centrifugal Pump: Uses a rotating impeller to impart energy to the fluid; widely used for water and low-viscosity liquids.
Positive Displacement Pump: Transfers a fixed amount of fluid with each cycle; includes gear pumps, piston pumps, and diaphragm pumps.
Reciprocating Pump: Uses a piston or plunger to create pressure; common in high-pressure applications.
Section 8: Submarines
Submarines are watercraft designed for deep underwater operations. They are capable of independent underwater travel and are used for various purposes, including military, scientific research, exploration, and undersea cable maintenance. Submarines operate beneath the water's surface, providing advantages such as stealth and the ability to operate in environments that surface vessels cannot.
Submarines have a cylindrical or streamlined hull designed to withstand the high pressures encountered at depth. The hull is typically made of steel or other strong materials.
How Submarines Work
When an object is underwater, it pushes aside (or "displaces") an amount of water equal to its volume. Subs can sink, rise, and float underwater. Subs do all this by adjusting the amount of water and air in their ballast tanks. When the tanks are full of air, the sub weighs less than the volume of water it displaces and it floats. When the ballast tanks are flooded with water, the sub weighs more than the water it displaces, and it sinks. To rise again, the sub reduces its weight by pushing compressed air into the ballast tanks. The air forces the sea water out, and the sub goes up toward the surface. To move beneath the surface and to hover, the amount of water in a submarine's ballast tanks is made equal to the weight of the water it is displacing.
A deep-diving submarine used to explore the ocean is called a submersible. Submersibles are usually smaller than submarines. They are often equipped with external cameras, manipulating arms, and special lights. Submersibles are built to do specific jobs, not for long-distance travel. We use them to help us recover "black box" flight recorders from wrecked airplanes, bury cables in the sea floor, investigate ancient shipwrecks, map the ocean floor, look for signs of undersea earthquakes, study marine life, repair damaged offshore oil wells, take rock samples of the ocean floor, and study ocean currents.