1. Chemical Building Blocks
Chapter 2 – Solids Liquids and Gases
Section 1 – States of Matter

2. Vocabulary Solid Crystalline solid Amorphous solid Liquid Fluid
Surface tension
Viscosity
gas

3. States of Matter
Our world is full of substances that can be defined as being one of the three primary states of matter
Solids, liquids and gases
Solids, liquids or gases can be elements, compounds or mixtures.
Air is a mixture of gases, but is made from elemental gases.
To truly define a solid, liquid or gas, we must look at their properties.

4. Solids
If I pick up a rock, and just move it around the room, will it change shape?
If I take it outside right now, will it change shape?
Will it become bigger if I put it in a bowl?
No.
A solid has a definite shape and a definite volume.
This means it will keep its shape and volume in any position and in any container.

5. Particles in a solid
The particles in a solid are packed very close together.
Also, tightly fixed in one position.
The particles are NOT motionless, but because of the tight packing, they vibrate back and forth only a little bit.
All students in the hallway.

6. Types of solids
If in the solid, the particles form a regular, repeating pattern, crystals form.
Solids that are made up of crystals are called crystalline solids.
Salt, sugar, snow are examples
Always will melt at a specific temperature
In amorphous solids, the particles are not arranged in a regular pattern.
Plastics, rubber, butter, and glass are examples.
Does not melt at a distinct temperature, instead, may become softer or change into a new substance when heated.

7. Picture of a crystalline solid

8. Liquids Liquids have a definite volume, but no shape of its own.
This means if I have 100 mL of a liquid, and pour it into a new container, I will still have 100 mL, but it may be shaped differently.

9. Particles in a liquid
Particles packed ALMOST as tightly as in a solid, but not as close.
Particles can move around each other freely.
Usually in contact, but allows motion to occur.
Since particles can move around freely, liquids can move around (flow).
A liquid is a fluid, which is a substance which can flow.

10. Properties of Liquids
Surface tension is the result of an inward pull around the molecules of a liquid that keep them together.
Is why water forms droplets that bead up on a surface
Allows insects to “walk” on water.
Viscosity is a liquids resistance to flowing.
Viscous liquids don’t flow much at all
Low-viscosity liquids flow easy.

11. Gases Gases are fluids, like liquids.
How does breathing show that gases are fluids?
However, a gas has no set volume, or shape.
A gas will fill up whatever space it can.
Gas particles stay apart from each other, and move around a LOT.
Because they move around a lot, they fill up whatever space they can!

12. Chemical Building Blocks
2.2 – Changes of State

13. Vocabulary Melting Melting point Freezing Vaporization Evaporation
Boiling
Boiling Point
Condensation
Sublimation

14. Physical State and Temperature
Remember, particles of a substance with higher temperature have higher thermal energy.
Thermal energy ALWAYS moves from warmer substance to cooler substance.
Particles of a liquid have more thermal energy than particles of the same substance in solid form.
As a gas, has even more thermal energy.

16. Changes between solid & liquid
Change of state from solid to a liquid is called melting.
This involves an increase in thermal energy.
In most pure substances, melting occurs at a specific temperature called the melting point.
Melting point often used to identify a substance.

17. What is Happening Melting Increased thermal energy
Particles move faster, more
Faster moving particles = higher temperature
Eventually, move enough to separate from each other enough to become a liquid
At the melting point, the particles of a solid substance are vibrating so fast they break free from their fixed positions.

18. Freezing When freezing, the reverse of melting occurs
Loses thermal energy
Particles slow down
Temperature decreases
At freezing temperature, the particles of the liquid are moving so slowly they begin to form regular patterns (i.e. solid!)
Melting and freezing temperature are the same thing!

19. Changing Between Liquid and Gas
The change from liquid to gas is called vaporization.
Vaporization takes place when the particles in a liquid gain enough energy to form a gas.
There are two main types of vaporization
Evaporation
Boiling

20. Evaporation
Evaporation is vaporization that takes place at the surface of a liquid.
Shrinking puddle is an example
Water in puddle gains energy.
The added energy allows SOME of the water molecules on the surface to escape into the air.
Or, evaporate.

21. Boiling
Boiling occurs when a liquid changes to gas below the surface as well as at the surface.
You see the results as bubbles form.
The temperature at which a liquid boils is called its boiling point.
As you heat up the liquid
Thermal energy increases
Particles move faster
Temperature increases
At boiling point temperature, particles have enough energy to move away from each other enough to be a gas.
Also used to identify an unknown substance.

22. Boiling Point and Air Pressure
Boiling point depends on the amount of air pressure.
The less air pressure, less energy is needed for the particles to escape into the air.
Less energy needed = lower boiling point.
In Denver, CO, water boils at 95°C, not 100°C like at sea level.

23. Condensation The opposite of vaporization
Condensation occurs when a substances changes from a gas to a liquid.
The particles in the gas must lose thermal energy for this to happen.
Water vapor is impossible to see.
When you see steam, really seeing the tiny droplets of water suspended in the air.

24. Changes Between Solid and Gas
It happens!
Sublimation occurs when the surface particles of a substance gain enough energy to form a gas.
During sublimation, particles do NOT pass through the liquid state to form a gas.

25. Chemical Building Blocks
2.3 – Gas Behavior

26. Vocabulary
Pressure
Boyle’s Law
Charles’ Law

27. Measuring Gases
Whenever we deal with something, like to be able to measure it in some way.
Making quantitative measurements
When we work with a gas, we want to know three things
Volume
Temperature
Pressure

28. Volume of gasses Already discussed volume in previous chapter
Because gas particles fill up any available space, volume of gas = volume of container.

29. Temperature of gasses
Remember: Temperature is the measure of the average energy of particles moving in a substance.
Faster particles = higher temperature
At room temperature (20°C), the average gas particles moves at 500 meters per second (more than 2x cruising speed of jet airplane).

30. Pressure Pressure is a force (push) divided by area being pushed.
Or, Pressure = Force / Area
Difference between sharp and dull knife. Which would have more pressure?
With a gas, pressure is the force of its outward push divided by the area of the walls of the container.
Measured in units of pascals (Pa) or kilopascals (kPa) (1 kPa = 1000 Pa)

31. The “firmness” of a gas-filled object comes from the pressure of the gas.
“Firmer” objects have higher pressure
Higher pressure is due to a greater concentration of particles inside the gas-filled object.
If a hole is punched in the container, particles will leave the higher-concentration area to go to the lower-concentration area.

32. Pressure & Volume Bag demonstration
As I push bag, what happens to volume?
What happens to firmness of the bag?
Boyle’s Law states that when the pressure of the gas at constant temperature is increased, the volume of the gas decreases.
What does this mean if the pressure is decreased?
Relates pressure to volume.

33. Weather balloons
High altitude weather balloons float because of helium gas inside of them.
High altitude = low pressure
What would happen to the balloon if they filled it up all the way on the ground?

34. Pressure and Temperature
Remember, the faster particles are moving means the higher the temperature is.
Faster moving = hitting walls of container more often.
Hitting walls of container more often =
Higher pressure
When the temperature of a gas at a constant volume is increased, the pressure also increases.
Truck-driver tires.

35. Volume and Temperature
Charles’ Law brings these together. Higher volume = higher temperature (for a constant pressure).