Why does one can float and the other sink? What do each can weigh? If two items have the same volume, what else can we measure about them? If two items have identical mass but different size, what does this mean?

Density Mass, Area and Volume

Units of measurement Scientist use universal units called S.I Units S.I stands for Systéme International d’unités It is French because they promoted it first LengthMassTimeTemperatu re AreaVolumeSpeed S.I. units metres Kilogra ms second s Degrees Celsius Metres squared Metres cubed metres per second Symbolmkgs 0C0Cm2m2 m3m3 m/s Equipm ent Metre stick Electro nic balance Clock, stopwa tch Thermomet er

Instruments

Area The area of a shape is the amount of surface enclosed within its boundary lines Area = Length x Width

Volume The volume of an object is the amount of space it takes up Unit : Cubic meters ( m 3 ) Cubic Centimetres (cm 3 ) Litre (l)

Measuring the volume of a liquid At home? Measuring jug In the Lab? Graduated Cylinder Burette Steps 1. Pour water into the cylinder 2. Read the volume by looking at the bottom of the meniscus!! (The curved part)

Measuring the volume of a solid Volume = Length x Width x Height Measuring the volume of an irregular shape The volume of say a stone is found by a method called displacement We measure the difference in water movement For larger objects we may need to use a displacement can or overflow can

Displacement

Density The density of a substance tells us how much mass is packed into a particular volume The unit for density is grams/cm 3

Manipulating the Formula The formula for density can be manipulated in different ways according to what information we have and what we need to find out 1. Density = Mass/Volume 2. Mass = Density x Volume 3. Volume = Mass / Density

Density Experiments

Stations 1. Regular Solid 2. Irregular Solid 3. Liquid

Density of Regular Solid Apparatus:  A rectangular Block  Balance  Ruler Steps 1. Find the Mass 2. Find the Volume

Density of an Irregular Solid Apparatus:  Overflow can  Potato/Rock  Balance  Graduated Cylinder Steps: 1. Find the mass of the stone/potato 2. Find the volume of the stone 3. Calculate Density

Density of a Liquid Apparatus:  Graduated Cylinder  Balance  Liquid Steps 1. Measure 25cm 3 of the liquid into a graduated cylinder 2. Find the mass of the liquid using a balance

Results

Floatation

Why do boats float in the sea? Why do twigs float in rivers? Why do icebergs float? All answers relate to densities of the objects or liquids

Floatation  A solid will float in a liquid if the solid is less dense than the liquid  A liquid will float on top of another liquid if the liquid on top is less dense

Density Table MaterialDensity g cm 3 Polystyrene0.002 Cork0.2 Paraffin Oil0.8 Ice0,9 Water1 Aluminum2.7 Mercury13.6 Gold19.3

Density Tower Liquids  Water  Honey  Maple syrup  Washing up liquid  Vegetable oil  Milk  Rubbing Alcohol/Acetone

Learning Check The units of density are g cm -3 or kg m -3 For numerical questions remember monkeys drink vodka A solid will float in a liquid if the solid is less dense than the liquid A liquid will float on top of another liquid if the liquid on top is less dense than the liquid on the bottom

Homework  Write up Density experiments  Homework Sheet  Density Test next week