P. Sci. Unit 7 Chapter 2 Matter

Chemistry What things are made of and how things change.

Matter Has mass and takes up space. Matter is made up of atoms Light sound and electricity are NOT matter

Atoms The smallest particle that has the properties of an element. Element – a substance that cannot be broken down into simpler substances. All the atoms in the substance are alike

Elements Each element has a one or two letter symbol used worldwide to designate it. The chart that shows all the known elements is called the Periodic Table of Elements.

Compounds When two or more elements combine chemically you get a compound.

Molecule The smallest unit of a substance that exhibits all the properties of that compound.

Chemical formulas The combination of chemical symbols (and how many atoms of each) make up a molecule of a substance.

Pure vs. Mixtures Pure substances – any substance that has a fixed composition and definite properties. Table sugar – C 12 H 22 O 11

Mixtures - A combination of substances that are not fixed; they can change OJ – is a mixture of water, citric acid and sugar among other things. Any drop of Orange Juice can have different amounts of the different components.

Classifications of Mixtures Homogeneous Mixtures – a mixture that is the same throughout (completely mixed) Heterogeneous Mixtures – a mixture where you can see all the parts. (incompletely mixed)

Properties of Matter Physical Properties Chemical Properties Physical Changes Chemical Changes Changes of Matter

Physical Properties characteristics of a material which can be observed without changing the identity of the substances in the material. examples include color, shape, size, melting point, and boiling point.

Appearance – physical description of a substance. Behavior – how a substance acts; for example, magnetism, viscosity, ductility. Physical properties such as size and magnetism can be used to separate mixtures.

Chemical Properties Characteristics of a substance indicating that it can change chemically.

Examples: flammability or light sensitivity of a substance, production of a gas, production of a precipitate, change in odor.

Physical Change A change in a substance’s physical property (properties). Substance does not change identity when it undergoes a physical change. Examples: change in size, shape, or state of matter

Chemical Change When one substance changes to another substance. Some chemical changes are indicated by temperature change, smell, or bubble formation.

Other chemical changes occur very slowly such as the formation of rust.

Density The mass per unit volume of a substance. (how much matter is packed into a specific amount of a substance) d = m/v Density is a physical property.

Dissolving When a substance dissolves, it seems to disappear because the particles of the substance spread out between the particles of the liquid. Neither substance changes into another substance, therefore: Dissolving is a physical change.

Change of State When a substance goes from one state of matter to another the substance does not change into another substance. (ice, water, steam – are all H 2 O) Therefore – Change of State is a Physical Change.