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## DENSITY

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**There are three phases of matter:**solid liquid gas**Gas**Solids Liquids Density – how close together the molecules are Molecules close together Molecules spread out further Molecules spread far apart**To determine density, you must divide the mass by the**volume. Density = mass volume**We can determine the mass of the box using the digital**scale. 750 g**Some units for mass….**• grams (g) • kilograms (kg) • milligrams (mg) • 1000 g = 1 kg • 1000 mg = 1 g • 1 000 000 mg = 1 kg ….and conversion factors**Volume of a regularly-shaped object can be measured using a**ruler.**Some units for volume….**• cubic centimeter (cm3) • milliliter (mL) • liter (L) • 1 cm3 = 1 mL • 1000 mL = 1 L ….and conversion factors**If the object has smooth sides where a ruler can be used to**measure the length, width, and height, it is considered regular-shaped.**Volume = length x width x height**2 cm 5 cm 15 cm**V = l x w x h**V = 15 cm X 5 cm X 2 cm V = 150 cm3**mass**= Density Volume m D V**mass**= Density Volume 750 g D 150 cm3**mass**= Density Volume 750 g 5 g/cm3 150 cm3**V = l x w x h**V = 3 cm X 3 cm X 3 cm V = 27 cm3**A piece of silver has a mass of 2800 grams and occupies a**volume of 266 cm3. What is the density of silver?**If a block of copper measures 2.00 cm x 4.00 cm x 5.00 cm**and its mass is 356 grams, what is its density?**Volume of a liquid is measured in mL using a graduated**cylinder, beaker, or flask.**Objects that do not have smooth sides to measure are called**irregular-shaped. To measure the volume of these objects we use water displacement.**50**40 30 20 10 Water is put into a graduated cylinder and the volume of the water is measured.**The object is placed in the graduated cylinder.**50 40 30 The volume of the water and the object is determined. 20 10**The first volume is subtracted from the second volume.**40 mL – 29 mL = 11 mL The volume of the object is 11mL.**Density does not depend on the amount of the substance**(intensive property). The density of the block is 16 g/cm3**If it is cut in half, what happens to the density?**Density of block is 16 g/cm3 Density of block is 16 g/cm3**Another example of buoyancy is a hot air balloon. The air,**a fluid, buoys the balloon.**Some organisms use buoyancy to move. An example is the**jellyfish.**If an object with a density of less than 1g/mL is placed in**the water, it will float.**If an object with a density of greater than 1g/mL is placed**in the water, it will sink.**The density of the liquid determines if the material placed**in it will float or sink.**We can make a density column to demonstrate the different**densities of materials.**Alcohol**Oil Water Density = 1g/mL DENSITY COLUMN Can you give an estimation of the density of the alcohol and the oil?**Alcohol**Oil Water Density = 1g/mL DENSITY COLUMN The density of the oil is less than 1 g/mL. The density of the alcohol is less than the density of the oil.**DENSITY COLUMN**Estimate the density of the piece of wood. Alcohol Density = .75 g/mL Oil Density = .96 g/mL The density of wood is .8 g/cm3. Water Density = 1g/mL**DENSITY COLUMN**Estimate the density of the piece of ice. Alcohol Density = .75 g/mL Oil Density = .96 g/mL The density of ice is .9 g/cm3. Water Density = 1g/mL**Fluids can flow, but not all fluids flow quickly.**Viscosity is defined as the resistance to flow.**Some fluids move slowly. They have a high viscosity.**Syrup pours slowly. It is very viscous.**Some fluids move quickly. They have a low viscosity.**Water pours quickly. It is less viscous.**We can compare viscosity by putting a drop of three**different fluids on a board and then tilting the board. 1 2 3 Fluid #1 was the least viscous. Why? Which fluid was the most viscous? How could you tell?