Matter: has mass and takes up space
The Particle Theory of Matter helps explain how particles exist and act in solids, liquids and gases.
The PTM states that:
1. All matter is made up of very tiny particles
2. There is space between particles
3. The particles are always moving. The more energy they have, the faster they move.
4. There are attractive forces between particles.
5. All particles in a pure substance are the same but are different from other substances.
The 3 states of matter are solid, liquid and gas. They can be described in terms of their shape, volume, particle arrangement and particle movement. Please see and study the table on the next page.

State of
Matter
Solid
Liquid
Gas
Shape
Definite – cannot change shape to fit containers
Indefinite – liquids will change their shape to fill up any container they are put in
Indefinite – a gas has an indefinite shape because it will change its shape to fill any container in which it is contained
Volume
Definite – we cannot change the volume of a solid without cutting it, which is physically changing it. A solid will not grow or shrink on its own!
Definite – you cannot change the volume of a liquid. If you glass of water you have a glass of water! The water does not grow or shrink!
Indefinite – a gas has an indefinite shape because it will expand (get bigger) and contract (get smaller) to fill the shape of a container
Particle
Arrangement
Close – particles are very close together
Particle
Movement
Vibrate – hit into and rub up against one another but cannot float away or slide past each other.
Particles are very attracted to each other
Close, but not as close as a solid. Not packed so tightly
Far apart – there is a lot of space between the particles
Free Flowing – they are able to move around more freely and can slide past each other. They have enough energy to pull away from one particle but are then attracted to another particle.
They are always changing partners!
Random – the particles float around randomly. Free to move in any and every direction. Gas particles have so much energy that they continually collide and bounce off each other and stay suspended in mid-air.

- A Fluid is any form of matter that FLOWS.
- Since liquids and gases do NOT have definite shapes, they are able to flow – making them both FLUIDS
- We use fluids in our lives every day…
- Food Fluids: water, oil, syrup, honey
- Cleaning Fluids: shampoo, detergents, gels, VIM, Mr. Clean
- Bodily Fluids: blood, mucus, saliva
- Industrial Fluids: lube, oil, gas, compressed air in tires
- Viscosity is a measure of a liquids resistance to flow.
- We say that fluids are thick (syrup) or thin (water)
- A fluid that is VISCOUS is one that is NOT runny and flows very slowly, like molasses!
- Friction is a force that resists movement.
- The greater the FRICTION (or rubbing of particles) the greater the VISCOSITY.
- When an object his highly viscous we know that the particles are holding on tight to one another! They are very attractive to one another.

We need to use fluids for specific purposes. We depend on fluids having particular viscosities in order to be able to use them! For example:
- Paint – we need paint to not be too runny (too viscous) or it would not spread on or stay on our walls!
- Foods such as ketchup and mustard must be kept in the fridge so that the cool temperatures keep them more viscous. If they were too runny we would have difficulty getting them to stay on our food. Also, if peanut butter were kept in the fridge, the cold temperature would keep it too hard to spread. That is why we keep peanut butter on the shelf when the warmer temperature makes it easier to use!
- Motor oils are needed to keep cars lubricated. We need to use high viscosity
(thick) motor oil in summers because the warm temperatures will make them runny
(less viscous) enough to properly lubricate your vehicle. In the winter we would need lower viscosity oil because the colder temperatures will make it more viscous and we wouldn’t want it to be too thick that it does not do its job.
- Flow rate is the speed at which a fluid flows from one point to another. Fluids can move slowly, quickly or at a medium speed.
Slow Flow Rate
Corn Syrup
Molasses
Medium Flow Rate
Dishwashing liquid
Some shampoos
Fast Flow Rate
Water
Sodas
High
Low
Viscosity
Slow
Fast
Flow Rate Description
Thick and more viscous
Runny and less viscous

1. Temperature
Liquids : Increase Temperature = Decrease Viscosity (becomes more runny)
Decrease Temperature = Increase Viscosity (gets thicker)
* According to the Particle Theory of Matter, when you add heat to a liquid the particles depend on the increase in energy to move them further apart so that they flow past each other easier (less viscous)
Gases : Increase Temperature = Increase Viscosity (expands, get bigger)
Decrease Temperature = Decrease Viscosity (contracts, gets smaller)
* According to the PTM, temperature affects gases and liquids differently because gas particles do not need an increase in energy (from temperature) to move farther apart because they are already far apart!
2. Concentration – the amount of a substance dissolved in a specific volume
Increase Concentration = Increased Viscosity
Decrease Concentration = Decreased Viscosity
- Pancake batter- we can alter how viscous pancake batter is by changing the concentration (amount) of batter or water in the mixture!
- According to the PTM, when we add more batter, we are adding more particles to the same volume of water. More particles mean more attractive forces and less room to move about, causing a higher viscosity.

3. Attractive Forces
Strong Attraction = More Viscous
Weak Attraction = Less Viscous
- The PTM states that the stronger the attractive forces between particles, the less likely they are to pull away from each other or slide past each other resulting in a more viscous fluid.
4. Particle Size
Small Particle Size = Less Viscosity (more runny)
Large Particle Size = More Viscosity (thicker)
- According to the PTM, small particles can move past each other more easily then large particles can because they take up less space and have more room to move.
- So, if we compare water and oil we know that the oil particles must be larger than the water particles because oil is more viscous and has a slower flow rate

- Density is the measure of the mass contained in a given volume.
- Density also describes how tightly packed together particles are in a material.
More dense materials have more particles packed closer together.
- Mass – the amount of matter in a substance
- Volume – the amount of space occupied by a substance
- Substances with lower densities will float on substances that have higher densities (just like we learned when we layered salty colored waters and the nonsalty waters in unit 1)
Particles
Density
Solids
Particles very close together
High density
Liquids
Particles close but can slide past
Gases
Particles very far apart from each other
Medium density Low density
- If we were to layer a solid, liquid and a gas, we would have the solid at the bottom, the liquid in the middle and the gas at the top!
- Water vapor (gas state) would be less dense than water (liquid state).
- The density of a pure substance is unique to that substance. The mass to volume ratio of a material is constant. This means that whether you have a cup of salt water or a bathtub full of salt water the density of salt water is the same if the mass to volume ratio is the same! If the mass of a substance increases, the volume will also increase.

Displacement – the space an object takes up when it is placed in a fluid. For example, if you had a full glass of water and you wanted to put a piece of wood in it, some of the water would pour out of the glass. The wood has “displaced” some of the water and we can use the displaced water to figure out how much space the wood took up!
Density = mass / volume
The density of a solid is given in g/cm3
The density of a liquid in g/mL
Students should be able to manipulate the Density formula to solve for mass and volume!
Sample Problems
1. Find the density of a 10 g mass of a substance that has a volume of 2.0 cm 3 .
D = m/V
D = 10 g / 2.0 cm 3
D = 5.0 g/cm 3

2. What is the density of 25 g of a substance placed in 10 L of a liquid?
D = m/V
D = 25 g / 10 L
D = 2.5 g/L
3. The density of a substance is 9 g/cm 3 . If the object has a mass of 27g, what is the volume?
V = m/D
V = 27g / 9 cm 3
V = 3 cm 3
4. What is the mass of a substance that has a density of 50 g/mL and a volume of 2 mL? m = D x
V m = 50 g/mL x
2 mL m = 100 g
Assignment: Practice Problems
Page 312 # 1, 2,3
Page 313 # 1,2,3
Page 314 # 1,2,3

Increase Temperature = Decreased Density
Decrease Temperature = Increased Density
- According to the PTM, increasing temperature will cause the particles in a substance to gain energy and spread out, thus taking up more space. This results in it being less dense.
Hot Air Balloons – the inside of the balloon is heated. As the particles gain energy from the heat, the air particles inside the balloon begin to move around and spread further apart from one another. As the density of the air in the balloon decreases, it becomes less dense than the air around the balloon and will rise. The pilot can control the balloon by controlling the heat that enters the balloon.
Tire pressure – as temperatures decrease in winter months the particles inside the air in the tires lose energy and take up less space. The density of the air has decreased and the tired deflates a little. In summer, the heat causes the particles to gain energy and expand, inflating the tire.
Drying wood – freshly cut wood is much heavier than wood that has been dried out because of the amount of water in the tree. Once the tree is left to dry, the water particles in the wood evaporate and are replaced with air. The air is less dense than water, making the dry wood less dense than fresh wood.
Swimming – Easier to float in salt water than fresh water because the density of salt water is gr eater than that of fresh water and can support more of your body weight!
Submarines – submarines are able to sink and come back to the surface by taking on or getting rid of water. Again, as the submarine gets rid of water, the space is replaced with air which is less dense, allowing the submarine to rise to the surface.

Force – anything that causes a change in the motion of an object, such as a push or a pull
Balanced Forces – balanced forces are equal in strength but opposite in direction and there is no movement.
Examples of balanced forces:
Unbalanced Forces – unbalanced forces are unequal in strength and cause a change in speed or direction. An object will continue in the direction toward which the greatest force is pushing.

Newton – we measure force in Newton (N)
Weight – A measure of the force (pull) of gravity on an object
Mass – the amount of matter in a substance
Weight looks at the gravity on an object and will change if the gravitational forces change – for example, your mass on earth would be different if you landed on the moon, on Jupiter or anywhere else in the universe. Mass, however, does not change no matter where you are in the universe.
- The higher the weight in Newton, the higher the force of gravity. Which of the following planets would have the least amount of gravity? It would be Mercury because it has the lowest weight in Newton.
Planet Weight (Newton)
Earth
Mercury
Venus
680
240
572

- Buoyancy is the upward force of an object submerged or floating on fluids.
- A buoyant force pushes away from the center of the earth; gravity will pull you toward the center of the earth. The forces work against each other.
- An object that floats has NEUTRAL BUOYANCY. This happens when the force pulling down (gravity) equals the force pushing up (buoyancy).
- Floating does not necessarily mean directly on top of the water… an object may float in the water or under the surface and still have neutral buoyancy.
- An object will sink into the fluid until it has displaced a volume of fluid that has the same weight as the object. Then, it will float.
- If it cannot displace enough water to match its weight, the object will continue to sink because its gravity force is larger than its buoyant force. These are unbalanced forces.

- If the density of an object is greater than the density of the fluid you put it in, then the object is going to sink!
- Average Density – the total mass of all substances that make up an object divided by the total volume.
- Because of average density, objects that would normally sink are able to float.
Example : Boats are made of steel which has a density of 9.0 g/cm 3 . As long as they have large, hollow hulls that can fill with air (which has a density of 0.0012 g/cm 3 ) it will be able to float. We can look at the average density of the boat filled with air which will be less dense than the water in which the ship will be placed in!
Wooden boat versus water logged stick
- Wooden boat will have an average density of wood + air and will have a lower average density than the water it is placed in so it will float. A water logged stick has the average density of wood + water which will have a higher average density than the water it is placed in and will sink.
Metal block versus Metal boats
- A metal block is a solid block that has a higher density than water so it will sink.
We are not combining the density of it with anything else, so it is not able to use the average density idea in order to sink. When we build the metal boat, we are now combining the density of the metal with air that will fill the boat and the average density is smaller and will be able to float.
Sealed empty plastic bottle versus plastic bottle full of water
- a sealed, empty bottle is not really empty. It has air trapped inside of it. The average density of the bottle + air will be small so it will float. The bottle full of water has an average density of bottle + water will be higher than the density of the water it will be placed in so it will sink.

- Personal floatation devices – when worn, they allow your body to have a lower average density and you are then able to float in the water and not drown
- Submarines – allow water to flow in and out. When the weight of the submarine
+ water is greater than the buoyant force, it will sink. When the water is let out of the submarine, it weighs less, is less dense and will come to the surface.
- Hot air balloons – the air inside the balloon heats up and spreads out, forcing some of the particles out of the balloon. The air inside of the balloon then becomes less dense than the air surrounding the outside of the balloon allowing the balloon to rise.
- Pressure is the force acting on a certain area of a surface. When you press your hands against a wall you are applying pressure on that area of the wall!
- The unit for measuring pressure is called the Pascal (Pa).
- Atmospheric pressure – the amount of force that is exerted by the weight of the atmosphere.
- The larger the force, the greater the pressure.
- The smaller the area, the greater the pressure.

Pressure = Force / Area
- Students should be able to manipulate the formula to solve for F and A as well.
- Students should recognize that N/m 2 = Pa
- Area – the amount of space something takes up, calculated in m 2
Sample Problems
1. An aquarium is filled with water that weights 10 000 N. If the base of the aquarium has an area of 1.6 m 2 , what pressure does the water exert on its base?
P = F / A
P = 10 000 N / 1.6 m 2
P = 6250 Pa
2. If the pressure is 101 200 Pa and you are holding your hand out, the atmosphere is exerting a force on your hand. If the area of your palm is 0.006 m 2 , calculate the force on your hand.
F = P x A
F = 101 200 Pa x
0.006 m 2
F = 607 N

3. The weight of water in a glass is 4.9 N. If the water is exerting a pressure of
1700 Pa on the bottom of the glass, what is the area of the bottom of the glass?
A = F / P
A = 4.9 N / 1700 Pa
A = 0.0029 m 2
Assignment
Practice problems on page 351 – 353
Hydraulic system – hydraulics is the study of pressure in liquids. Hydraulic systems are systems that apply force on liquids to move other objects.
Since water has a definite volume, it is incompressible . This means it cannot be squeezed into smaller containers. For example, ALL OF the water in a large glass cannot be forced into or compressed into a smaller glass.
The liquid in a hydraulic system must be in tubes, hoses or pipes which cause pressure to be exerted equally in all directions and eventually will push through the end of the system forcing something to move.
Examples of hydraulic systems are dentist or hair dresser chairs and dump trucks,

Pneumatic system – pneumatics is the study of pressure on gases. Pneumatic systems are systems that apply force on gases to move other objects.
Gases have an indefinite volume and can therefore be compressed or forced into smaller containers. This creates a build-up of air pressure that when released pushes air particles apart quickly creating a strong, steady force that can perform powerful tasks.
Examples of pneumatic systems are jackhammers, dentist drills and air brakes in trucks and buses.
Hydraulics versus Pneumatics Chart
Property
State
Volume
Pressure
Hydraulic System
Liquid
Definite
Not compressible
Pneumatic System
Gas
Indefinite
Compressible
Pascal was a 17 th century scientist that studied pressure.
Pascal’s Law states that pressure applied to an enclosed fluid is transmitted with equal force throughout the entire container. This is the basics of both the hydraulic and pneumatic systems
Examples of Pascal’s Law can be found when we use:
1. Car lift or hoist
2. Hydraulic jacks
3. Automobile breaking systems
4. Air compressors
5. Squeezing a tube of toothpaste

- If we increase the pressure on a gas, we decrease the volume of the gas.
However, the temperature must be constant.
* We see this in aerosol cans, paint ball guns, spray paint, whipped cream, propane tanks… These are highly pressurized, which allows us to fit a large volume into a small can!
-If we increase the temperature on a gas, we increase the volume. However, the pressure is constant.
* We see this in hot air balloons or gas cans on a hot day. When its warmer, the gas particles move further apart causing the air/gas to increase in volume.
- If we increase the temperature of a gas, we increase the pressure. However, the volume is constant.
* If we heat sealed containers eventually the containers will explode because we have increased the pressure of the fluid.