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Matter. Chapter 2. 2-2 Objectives. Distinguish between the physical and chemical properties of matter and give examples of each. Perform calculations involving density Explain how materials are suited for different uses based on their physical and chemical properties, and give examples
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Matter Chapter 2
2-2 Objectives Distinguish between the physical and chemical properties of matter and give examples of each. Perform calculations involving density Explain how materials are suited for different uses based on their physical and chemical properties, and give examples Describe characteristic properties, and give examples
Physical Properties • Something you can measure on an object without changing what it is (at a molecule level) • Examples: Color, mass, density, texture, volume, boiling point, melting point
Physical Properties Identify Matter • We can use the physical properties to determine what an object is. • For example: • Pure water is always colorless, odorless • Liquid at room temperature and has a boiling point of 100°C and a freezing point of 0°C at normal atmospheric pressure
Physical Properties Identify Matter • Physical properties also help us determine the best way to use various substances. • For example: • We use aluminum pans for cooking because they conduct heat very well and have high melting points. • Both physical and chemical properties help us identify matter • These are called the “characteristic properties” of that substance.
Chemical Properties • Properties of a substance that relate to how they react with other substances. • We can only measure these as the substances are changing in the reaction! • These are not very easy to measure (this is happening at a molecular level!) • Words we use to represent chemical properties: • flammability • decay • reactivity
Measuring Density • “How many atoms we have in a certain amount of space” • Measured mass/volume (m/v) • Units are g/mL or g/cm3
Density Practice If 10.0cm3 of ice has a mass of 9.17 g, what is the density of ice? D = m = 9.17 g v 10.0 cm3 D = 0.917 g/cm3 We will complete some practice problems at the end of these notes.
2-3 Objectives Explain physical change, and give examples of physical changes Explain chemical change, and give examples of chemical changes Compare and contrast physical and chemical changes Describe how to detect whether a chemical change has occurred.
Physical Changes • Changing a physical property of a substance without changing its identity. • Words that describe physical changes are: • cutting • melting • dissolving • mixing • freezing
Changes? • It may look like changes are occurring during a physical change, but things are staying the same at the molecular level!
Types of Mixtures • Homogeneous • It looks the same throughout • Also called a solution • Only one phase (one state of matter or looks the same) • Heterogeneous • It looks different throughout the sample • Has more than one phase (state of matter or different parts look different)
Separating Mixtures • Mixtures are separated by physical changes. • Can be done easily and other times elaborate methods must be used. • The identities of the substances in the mixture stay the same throughout the process
Methods of Separation • Physical Separation • Evaporating • Filtering • Centrifuge • Distillation • Magnetism
Chemical Changes • The ability to change into a new substance with different properties • Words you hear referring to chemical changes are: rot, ferment, burn, rust
It Changes into Something New • This….. • Becomes this!!! • And it is VERY difficult to change back!!!
How Do We Know a Chemical Change Takes Place? • Color change • Fizzing • Gas given off • Odor change • Heat change • Light given off • Sound given off
Separating Compounds • Compounds can only be separated by chemical changes • This can be done by reacting with another compound or element, or by running an electrical current through the compound.
