Elements Compounds and Mixtures 3 KINDS OF MATTER

Elements, Compounds, and Mixtures

3 KINDS OF MATTER l. Elements l. Compounds l. Mixtures

Elements l All (living and nonliving) of the different kinds of matter in the universe is made from about 100 different substances, called elements. l Elements are called the building blocks of matter because all matter is composed of elements. l Each element is made up of the same type of atoms.

Compounds l A compound is a substance made of two or more different kinds of elements chemically combined in a specific ratio. l Each compound is represented by a formula that uses symbols to identify which elements are present. l A formula shows the ratio of elements in the compound. l H 2 O – ratio of Hydrogen is 2: 1 Oxygen

l The symbols make up the formula. A formula is just chemical shorthand for the compound. l The subscript lets us know how many atoms are present. l The coefficient lets us know how many molecules are present.

Compounds

Molecules l A molecule is formed when two or more atoms join together chemically. l Diatomic molecules are made of two atoms of the same element. l Hydrogen – H 2 l Oxygen – O 2

What is the difference between a compound a molecule? l A molecule is formed when two or more atoms join together chemically. l A compound is a molecule that contains at least two different elements. l All compounds are molecules but not all molecules are compounds.

l Molecular hydrogen (H 2), molecular oxygen (O 2) and molecular nitrogen (N 2) are not compounds because each is composed of a single element. l Water (H 2 O), carbon dioxide (CO 2) and methane (CH 4) are compounds because each is made from more than one element.

Molecule l The smallest bit of each of these substances would be referred to as a molecule. For example, a single molecule of molecular hydrogen is made from two atoms of hydrogen. l A single molecule of water is made from two atoms of hydrogen and one atom of oxygen.

Mixtures l Most matter in the universe is found in mixtures. l A mixture is made from two or more substances either elements, compounds or both - that are not chemically combined.

Mixtures and compounds differ in two ways… Substances in a mixture keep their individual properties. Parts of a mixture are not necessarily present in specific ratios.

Compound l A compound has properties different than the elements that make it up. l The parts of a compound are present in specific ratio’s.

Compounds and Mixtures l Most of the matter around you is in the form of compounds or mixtures. l Water, carbon dioxide, salt, vinegar, baking soda, lye, sugar, gasoline, and bleach are all chemical compounds.

Heterogeneous Mixture l A mixture in which different materials can be easily distinguished. l Pizza, dry soup, chex mix, trail mix are all examples.

Solutions l Homogeneous mixture: is a substance in which two or more substances are uniformly spread out. For example salt water. l Solution is another term for homogeneous mixture.

Solutions l Solute is the substance being dissolved. l Solvent is the substance that dissolves a solute. l Solubility is the amount of a substance (solute) that will dissolve in a solvent.

Example l Salt water: l The water is the solvent l Na. Cl is the solute

Colloids and Suspensions l A colloid is a heterogeneous mixture that like a solution never settles. Milk and smoke are examples. l One way to tell a colloid from a solution is because milk is appears white because its particles scatter light. Called the Tyndall Effect.

suspension l A suspension is a heterogeneous mixture containing a liquid in which visible particles settle. l River water

Na. Cl is the formula for salt

Water is H 2 O l An oxygen atom can bond with two hydrogen atoms to make a molecule we call water. Water is an example of a compound, because it contains more than one kind of atom. The formula for water is H 2 O, meaning there are two hydrogen atoms for each oxygen atom.

Carbon Dioxide CO 2 l Carbon dioxide molecules are made from one carbon and two oxygen atoms joined together by covalent bonds. The chemical symbol is CO 2.

Glucose - C 6 H 12 O 6

Molecule l When a compound is broken down into its’ smallest piece it is called a molecule. You should be able to write the formula for the following: l Water l Oxygen l Carbon Dioxide

DNA l Is a large molecule made up of carbon, hydrogen, nitrogen, oxygen, and phosphorous.

Kinetic theory of matter l The idea that all matter is made up of constantly moving tiny particles.

l Elements form compounds to try to fill their outer energy level with valence electrons. l This is called chemically stable. If the atom is not chemically stable it will lose, share, or gain electrons. l A chemical bond is the force that holds together the atoms in a substance.

Ion l l l An Ion is an atom or group of atoms that has become electrically charged. A When an atom loses an electron it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Forming an Ionic Bond: l. Sodium has one valence electron and transfers that electron to chlorine l Na + Cl- the negative and positive electrical charges attract each other so the oppositely charged ions come together and form sodium chloride (salt).

l An ionic bond is the attraction between two oppositely charged ions. This attraction is similar to the attraction between opposite poles of two magnets. l.

l When two ions come together the opposite charges cancel out. l Compounds are electrically neutral. When the ions come together they do so in a way that balances out the charges on the ions

Molecules and Covalent Bonds l The attraction that forms between atoms when they share electrons is known as a covalent bond.