Determining Density

In order to be able to determine densities we should learn: Units Measurement of Length Measurement of Volume Measuring Mass and Weight

Units SI Units The following table gives SI units for the basic physical quantities (things that can be measured). All scientists throughout the world use these units. (SI from the French “Le Systeme International d'Unites”.)

SI Units Physical Quantity cal S SI Unit nit Symbol m Mass second A TemperatureKelvin Amount of substanceMolemol Luminous intensityCandelacd Length Time Electric Current metre kilogram kg s ampere K

Units Prefixes Used to express physical quantities that are very big or very small. Although metres are the SI unit for length we use other units based on the metre. Small objects will be measured in centimetres millimetres or micrometres. Large objects will be measured in kilometres.

PrefixMeaning Symbol Micro  1,000,000  Milli  1,000 m Centi  100 c Deci  10 d Kilo 1,000k Mega 1,000,000M Prefixes

Units conversions Express 5600 m/s in units of km/h

…. and a tricky one!

Reading measuring cylinders Precautions Always take the following precautions when reading the volume of a liquid: 1. Place the container on a flat horizontal surface. 2. The eye must be positioned perpendicularly at the mark of the scale. This is to avoid errors in measurement due to parallax. Q.What are the readings on the following measuring cylinders? (Scales in cm³.)

Measuring Densities: Direct Method Regular Solids Volumes can be calculated by taking measurements then using formulae. 3 cm 2 cm Volume of rectangular block = Volume of cylinder =

Measuring densities: Archimedes way or the high-way Irregular Solids 1. Volume of a small irregular solid that sinks Irregular Solids 2. Volume of a small irregular solid that floats

Measuring densities: Archimedes way or the high-way Irregular Solids 3. Volume of a larger irregular solid