Section 3: Describing Matter

physchemchange 1024x683 - Section 3: Describing MatterAll matter has both physical and chemical properties.  Physical properties are those that can be observed without changing the make-up, or identity, of the matter.  For example, if you tear up a piece of paper, it does not change what it is made of.  Similarly, if you crumple up a piece of paper, the make-up is still the same.  However, if you were to set that piece of crumpled paper on fire, you have taken the paper and turned it into ash.  Flammability is a chemical property, which means it’s a property that has the ability to change something into a new kind of matter with different properties.  Physical properties include color, hardness, density, and boiling and melting points.  Chemical properties include flammability, combustibility, acidity, and ability to rust.

physical and chemical change 1024x683 - Section 3: Describing MatterA physical change is a change in size, shape, or state of matter.  The substance does not change its identity when it undergoes a physical change.  When water freezes, it becomes a solid, but it is still water.  Its composition has not changed.  Physical changes can be reversed.  If we heat an ice cube, it melts back into water.  A chemical change is a change from one substance to another substance.  The beginning substances called reactants change into different substances called the products.  A firework exploding is an example of a chemical change.  It’s important to note that during a chemical change mass is neither gained nor lost.

The law of conservation of mass says that the mass of all substances present before a chemical change equals the mass of all substances after the change.

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