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?

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

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

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)

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

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

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

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

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

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

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

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

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

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

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?

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