Section 3 - Classification of matter

• Matter is anything that has mass and takes up space.
• Matter can be divided into two main categories: pure substances and mixtures.
• A pure substance is a uniform substance made up of only one type of particle, which can be an element or a compound.
• Pure substances have the same composition and chemical structure throughout.
• Every sample of a certain element generally has the same intrinsic properties as every other sample of that element, with some exceptions.
• For example, on a nanoscale, gold may appear purple, black, or red.
• Every sample of a certain compound generally has the same intrinsic properties as every other sample of that compound.
• Pure water and carbon dioxide gas are examples of compounds that are pure substances.
• A mixture is two or more pure substances that are combined physically but not chemically.
• A mixture can be classified as homogeneous or heterogeneous.
• The different components that make up a mixture have different properties.
• A tossed salad is a mixture because it is made of different components — lettuce, carrots, cucumbers, tomatoes, croutons and dressing.
• A tossed salad is a heterogeneous mixture because it is not uniform throughout.
• Salt water is made of salt and water.
• Salt water is a homogeneous mixture, so it looks the same throughout.
• The chemical structure (composition) of each component of a mixture stays the same.
• Scientists can separate mixtures into their original components.
• The different components of a mixture are arranged randomly.
• Salt and water can be combined to form a salt water mixture.
• The properties of a mixture may be different than the properties of each component.
• Pure water looks clear, but salt water may look cloudy.
• The components in salt water do not react chemically with one another and can be recovered from the mixture.
• The salt in salt water elevates the boiling point of the salt water mixture compared to the boiling point of pure water at the same atmospheric pressure.
• Water that comes out of a kitchen sink is not a pure substance.
• Tap water usually contains minerals or other substances, so tap water is actually a mixture.
• Only distilled water contains only water molecules and is considered a pure substance.
• Elements are considered the simplest substances. An element is made of only one type of atom. It is identified by it's atomic number.
• All matter is made up of elements of combinations of elements.
• Allotropes: different forms of the same element in the same physical state of matter.
• Two solid allotropes of carbon are graphite (pencil lead) and diamond. Why are two solid forms of the same element so different? The answer is that the carbon atoms are arranged in a different pattern.
• Only certain elements have allotropes. Some are carbon, oxygen, tin, phosphorous, and sulfur.
• Oxygen has two gaseous allotropes: diatomic oxygen and ozone.
• Tin has two sold allotropes: white tin (beta tin) and gray tin (alpha tin)
• A pure substance made up of two or more elements combined in a defined ratio is a compound.
• In nature, most elements are found in combination with other elements. They are found as compounds.
• Pure water is a compound of hydrogen and oxygen atoms bound together in a 2:1 ratio. ( 2 hydrogen: 1 oxygen).
• A binary compound is made up of two different elements, such as sodium chloride (NaCl) and carbon dioxide (CO2).
• A ternary compound is made up of three different elements, such as glucose (C6H12O6) or silver carbonate (Ag2CO3). Can you remember what the (Ag) in (Ag2CO3) stands for?

• HOMOGENEOUS MIXTURE: a type of mixture that is uniform throughout. The components are mixed evenly, so that the composition is consistent throughout. Differences in components of the mixtures are seen at the scale of atoms and molecules.
• What kind of mixture is Apple juice?

  Apple juice is a homogeneous mixture.