1. Review 3.2 How is density measured?
What is density?
How is density measured?
If one fluid is more dense, will it sink or float in a fluid that is less dense?

2. Unit A: Mix and Flow of Matter
3.0 Properties of Liquids and Gases
3.3 Density, Temperature, and Buoyancy

3. Review of Density Density is the amount of matter in a given volume
Not all substances have the same density
It is the kind of particles in a substance that are important in determining the density of a substance

4. Review of Calculating Density
Density is the mass (weight) per unit of volume (size)
Density is found by dividing the mass of a substance by its volume
Density (d) = Mass (m)
Volume (V)
Liquids and gases are usually measured in grams per millilitre (g/mL) or kilograms per litre (kg/L)
Solids are usually grams per cubic centimetre (g/cm3)

5. Particle Model of Matter helps explain Density
Remember the Particle Model?
It states that particles in a substance move more quickly when energy (heat) is added
As the particles become more active they move away from each other
As they move away the space between the particles gets bigger and therefore causes an increase in the volume of the substance

6. Particle Model of Matter helps explain Density
Although the number of particles stayed the same, the volume is increased
This is what effects the density, because:
Density (d) = Mass (m)
Volume (V) If the number of particles stays the same and the volume increases the density would decrease.
In other words, there is less particles in one spot because the area for them to travel is bigger

7. Example of Temperature’s Effect on Density
Think about swimming in a lake on a hot day
As the temperature rises outside the lake water begins to warm up
The water at the top surface of the lake is noticeably warmer than the water at the bottom
This is because the warm water has a lower density then the cooler water and therefore floats on top

8. Different Temperature, Different Density
One substance then can have different densities at different temperatures
What happens to a substance when it is heated?
It changes state

9. Different Temperature, Different Density
At low temperature it will be a solid, at higher temperatures it will be a liquid, and at even higher temperature it will be a gas.
A substance (except water) has a greater density at its solid state than its liquid or gas state

10. Changing Density by Changing Concentration
Another way to change a substances density is to add particles
Think of a salt water solution vs. regular water
Increasing the concentration of salt increases the density

11. Changing Density by Changing Concentration
Ex: In a regular lake you can float but it is not as easily as in a salt-water lake or sea
This is because the water is more dense (has more particles) in the salt water
The Dead Sea-Israel

12. Buoyancy
An object will sink when its density is greater than the density of the fluid it is in
When an object is in a liquid-gravity pulls it down
However, the liquid exerts and opposite force-called buoyant force. This force pushes upward

13. Buoyancy
When the density of a liquid is greater than the density of the object the buoyant force is greater than gravity, thus the object floats
When the density of the liquid is less than the density of the object, the buoyant force is less than gravity and the object will sink
Buoyancy is the tendency for an object to float when placed in a liquid

14. Applications of Buoyancy
Transportation Technologies
As the air balloon is heated it rises
Boats sink lower in fresh water than they do in salt water

15. Review ???Any Questions??? I have some for you… What is density?
What are two factors that affect density?
How does the Particle Model of Matter help explain density (in reference to temperature)
What is buoyancy?
What is buoyant force?

16. 3.3 Homework Do all vocabulary for 3.3
Do Check and Reflect for 3.3 on page 52