Classifying Matter

Let’s start small and work up from there. Atom – the smallest unit of an element that maintains the properties of the element Atom – the smallest unit of an element that maintains the properties of the element The can be physically mixed or chemically joined to make up other forms of matter The can be physically mixed or chemically joined to make up other forms of matter

Pure Substance A sample of matter, either a single element or a single compound, that has definite chemical and physical properties A sample of matter, either a single element or a single compound, that has definite chemical and physical properties Figure 14, Page 22

Physical Properties Characteristic of a substance that does not involve a chemical change Characteristic of a substance that does not involve a chemical change Examples: Density, color, hardness Examples: Density, color, hardness Does this test change the chemical make-up of the material? Does this test change the chemical make-up of the material? No No

Chemical Property Characteristic of matter that describes a substance’s ability to participate in chemical reactions Characteristic of matter that describes a substance’s ability to participate in chemical reactions Example: Oxidation, flammability, and combustion Example: Oxidation, flammability, and combustion Does this test change the chemical make-up of the material? Does this test change the chemical make-up of the material? Yes Yes

Figure 12, page 19

Elements A pure substance that contains only one kind of atom A pure substance that contains only one kind of atom It cannot be separated or broken down into simpler substances by chemical means. It cannot be separated or broken down into simpler substances by chemical means. All atoms of the same element have the same atomic number All atoms of the same element have the same atomic number Elements may bond in different ratios with itself. These are called allotropes. Elements may bond in different ratios with itself. These are called allotropes.

Compounds A pure substance that is made up of two or more different elements joined by chemical bonds. A pure substance that is made up of two or more different elements joined by chemical bonds. They are represented by formulas They are represented by formulas

Molecules The smallest unit of a substance that keeps all of the physical and chemical properties of that substance. The smallest unit of a substance that keeps all of the physical and chemical properties of that substance. It can consist of one atom or two or more atoms bonded together It can consist of one atom or two or more atoms bonded together In other words, molecules can be of the same element or of the same compound only In other words, molecules can be of the same element or of the same compound only

All of the following are molecules, but are they compounds or elements? Br 2 Br 2 H 2 O H 2 O O 2 O 2 O 3 O 3 C 12 H 22 O 12 C 12 H 22 O 12 Element Compound Element Compound

Mixtures A combination of two or more substances that are not chemically combined. A combination of two or more substances that are not chemically combined. Examples are air, ice tea, and even cake batter Examples are air, ice tea, and even cake batter The proportions of the substances can vary The proportions of the substances can vary

Mixtures can be homogeneous or heterogeneous Homogeneous mixtures have a uniform structure or composition throughout Homogeneous mixtures have a uniform structure or composition throughout Because of the even distribution, any two samples taken from the same homogenous mixture will have the same proportions of ingredients Because of the even distribution, any two samples taken from the same homogenous mixture will have the same proportions of ingredients Examples: Gasoline, air, and syrup Examples: Gasoline, air, and syrup

Mixtures can be homogeneous or heterogeneous Heterogeneous mixtures are not evenly mixed. Heterogeneous mixtures are not evenly mixed. Different regions of the same heterogeneous mixture will have different proportions Different regions of the same heterogeneous mixture will have different proportions Examples: Pulpy Orange Juice, chocolate chip cookie dough, and granite. Examples: Pulpy Orange Juice, chocolate chip cookie dough, and granite.

Visuals of Homogeneous and Heterogeneous Mixtures Figure 19, Page 26

Mixtures verses Compounds, How can you tell which is which? Compounds are two or more elements that are chemically bonded together. Compounds are two or more elements that are chemically bonded together. Mixtures are two or more substances physically mixed together, but not chemically joined Mixtures are two or more substances physically mixed together, but not chemically joined

Therefore Properties of a mixture reflect the properties of the substances mixed in it; compounds have new properties of their own. Properties of a mixture reflect the properties of the substances mixed in it; compounds have new properties of their own. Compounds have definite composition; mixtures composition can vary from mixture to mixture of the same substances Compounds have definite composition; mixtures composition can vary from mixture to mixture of the same substances

In other words, You can have a mixture of hydrogen gas and oxygen gas in various concentrations, but the compound water, H 2 O, will always have 2 hydrogen atoms bonded to one oxygen atom. You can have a mixture of hydrogen gas and oxygen gas in various concentrations, but the compound water, H 2 O, will always have 2 hydrogen atoms bonded to one oxygen atom.

Figure 20, Page 28

Classify each of the following as an element, compound, homogeneous mixture, or a heterogeneous mixture Iron (III) Oxide (Fe 2 O 3 ) Iron (III) Oxide (Fe 2 O 3 ) 24 Karat gold 24 Karat gold Sugar Water Sugar Water Ozone Ozone Fizzy Soda Fizzy Soda Flat Soda Flat Soda Element Heterogeneous Mix Homogeneous Mix Compound

Separating Mixtures Since mixtures are just physically combined, they can be separated.

Separating Mixtures Some Methods include: Some Methods include: –Filtering – –Filtering – separation of a mixture’s components through differences in particle size –Decanting – a fancy term for separating two components by pouring –Distillation – used to separate two liquids based on their differences in boiling points –Magnetism – used to separate magnetic substances –Evaporation – removing a liquid to leave a solid behind –Centrifuge – separates substances of different densities using a fast rotational motion –Chromatography – Separates two substances by using a mobile phase and a stationary phase