7.2 properties of magma Key terms: element, compound, physical property, chemical property, viscosity, silica, pahoehoe, aa Key concepts: Why is it helpful to know the physical and chemical properties of a substance? What causes some liquids to flow more easily than others? What factors determine the viscosity of magma?

Physical and chemical properties An element is a substance that can’t be broken down further. A compound is a substance made of two or more elements that have been chemically combined. Each substance has a particular set of physical and chemical properties. These properties can be used to identify a substance or to predict how it will behave.

Physical properties A physical property is anything that can be observed without changing the composition of the substance. Examples: freezing point, melting point, malleability, density, hardness, magnetism

Chemical properties Any property that produces a change in the composition of matter. Examples: burning, tarnishing, rusting

Viscosity Viscosity is the resistance to flow. High viscosity – high resistance to flow. Low viscosity – low resistance to flow. High – honey. Low – water.

Viscosity of magma Depends upon its silica content. Not all magma has the same viscosity. Silica content – magma’s main ingredient. Made up of particles of the elements oxygen and silicon. Helps determine the viscosity – more – higher Magma high in silica produces light colored magma that doesn’t travel far

Temperature How does temperature affect viscosity? Viscosity INCREASES as temperature DECREASES. Pahoehoe (heeee hee heee heeeeeee!) and aa are two types of lava. Pahoehoe is fast moving hot lava with low viscosity Aa is cooler and slower moving with high viscosity