Units of Measurement Properties can be qualitative, like in the physical and chemical change lab, or quantitative. – numbers with a unit Some countries use the metric, US typically uses the English system. In 1960, an international agreement was reached which specifies the particular metric units for use in science. Section 1.4

SI Units Système International d’Unités Uses a different base unit for each quantity Know these Section 1.4

prefixes Sometimes the base unit is to small or too large. Those cases we add a prefix to the base unit – Run a 5K, 5 km instead of 5000 m – Ingest 500 mg of salt instead of kg

Metric System Prefixes convert the base units into units that are appropriate for the item being measured. Section 1.4 Know these and how to convert between prefixes Great many kids have dropped dead converting metrics, minus nine people!

Converting between units Start with given Put matching unit on bottom Put desired unit on top Set the larger unit = 1 Count the steps between the prefixes to determine the exponent on the smaller unit

325 mg to kg 325 mgkg mg 1 1*10 6 =3.25*10 -4 kg

25 km to  m 25 km mm km 1* =2.5*10 10  m

Temperature A measure of the average kinetic energy of the particles in a sample. In scientific measurements, the Celsius and Kelvin scales are used. K =  C Kelvin has no negative values – the absolute scale Fahrenheit is an o F = 9 / 5 o C + 32

Derived units A unit that is multiple base units put together.

Volume The most commonly used metric units for volume are the liter (L) and the milliliter (mL). A liter is a cube 1 dm long on each side. A milliliter is a cube 1 cm long on each side. Volume is a derived unit because it is more than one base unit, m 3. Section 1.4

Density Mass/volume Another derived unit The common unit for solids and liquids is g/cm 3 or g/mL Density broke my heart Section 1.4