Matter & The Atom

Matter The term matter describes all of the physical substances around us: your table, your body, a pencil, water, and so forth

Matter Anything that has mass and takes up space (has volume) Made up of different kinds of atoms

Matter Includes all things that can be seen, tasted, smelled, or touched Does not include heat, sound, or light

Matter is made of atoms

Models Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily

Models In the case of atoms, scientists use large models to explain something that is very small Models of the atom were used to explain data or facts that were gathered experimentally. So, these models are also theories

Early Models of the Atom Bohr Electrons move in definite orbits around the nucleus

Early Models of the Atom Chadwick Discovered the neutron

Modern Model of the Atom The electron cloud Sometimes called the wave model Spherical cloud of varying density Varying density shows where an electron is more or less likely to be

Atomic Structure Nucleus Protons Neutrons Electrons

Atomic Structure Electrons Tiny, very light particles Have a negative electrical charge (-) Move around the outside of the nucleus

Atomic Structure Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom 

Atomic Structure Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom 

Atomic Structure

Describing Atoms Atomic Number = number of protons In a neutral atom, the # of protons = the # of electrons

Describing Atoms Atomic Mass Number - equal to the number of protons plus neutrons.

Ions An atom that carries an electrical charge is called an ion If the atom loses electrons, the atom becomes positively charged (because the number of positively charged protons will be more the number of electrons)

Ions An atom that carries an electrical charge is called an ion If an atom gains electrons, the atom becomes negatively charged (more negative charges than positive charges)

Ions The number of protons does not change in an ion The number of neutrons does not change in an ions So, both the atomic number and the atomic mass remain the same.

Ions This atom has lost an electron. Now it has one more proton than electron. One more proton means one more positive charge. This makes the total charge of the atom POSITIVE. This atom has gained an electron. Now it has one less proton than electron. One less proton means one less positive charge. This makes the total charge of the atom NEGATIVE.

Mixtures, Elements and Compounds A Matter of Fact Mixtures, Elements and Compounds

Mixtures, elements, compounds Scientists like to classify things. One way that scientists classify matter is by its composition. Ultimately, all matter can be classified as mixtures, elements and compounds.

Why isn’t it a good idea to classify matter by its phases? Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.

Why isn’t matter classified according to its physical characteristics, such as color? Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.

Scientists ask themselves these questions? Is the matter uniform throughout? Can it be separated by physical means? Can it be separated by chemical means?

By asking these questions scientists can classify matter into: Mixtures – two or more substances that are not chemically combined with each other and can be separated by physical means. The substances in a mixture retain their individual properties. Solutions – a special kind of mixture where one substance dissolves in another. Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means. Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

Is it uniform throughout? If the answer is no, the matter is a heterogeneous mixture. Considered the “least mixed.” Does not appear to be the same throughout. Particles are large enough to be seen and to be separated from the mixture.

Examples of heterogeneous mixtures Sand and pebbles Oil and water Powdered iron and powdered sulfur

Granite is a heterogeneous mixture.

Is it uniform throughout? If the answer is yes, the matter is homogeneous (looks the same throughout). That leads us to another question.

Can it be separated by physical means? If the answer is yes, the matter is a homogeneous mixture or solution.

Homogeneous Mixtures A mixture that appears to be the same throughout. It is “well mixed.” The particles that make up the mixture are very small and not easily recognizable.

Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. They are also colloids.

Colloids In a colloid the particles are mixed together but not dissolved. The particles are relatively large and are kept permanently suspended.

Colloids A colloid will not separate upon standing. The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.

Solutions A solution is a type of homogeneous mixture formed when one substance dissolves in another. It is the best mixed of all mixtures. A solution always has a substance that is dissolved and a substance that does the dissolving. The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.

Ocean water is a solution

The universal solvent: Water

Water as a solvent Many liquid solutions contain water as the solvent. Ocean water is basically a water solution that contains many salts. Body fluids are also water solutions.

Metals dissolved in metals are called alloys. Types of solutions Solute Solvent Example Gas Air (oxygen in nitrogen) Liquid Soda water (carbon dioxide in water) Solid Ocean water (salt in water) Solid Gold jewelry (copper in gold) Metals dissolved in metals are called alloys.

Alloys Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.

Mixtures CAN be separated by physical means Filters (colander) Heat (saltwater) Physical separation (m&ms) Mixtures are broken down into compounds or molecules

Can it be separated by physical means? If the answer is no, the matter is a pure substance. An element Or a compound Compounds can be broken down into elements

Elements Elements are the simplest pure substance. An element can not be changed into a simpler substance by heating or any chemical process. The smallest particle of an element that has the properties of that element is called an atom. An atom is the basic building block of matter. There are more than one hundred known elements in the universe listed on the periodic table of elements. These elements combine in such a way to create millions of compounds.

Elements All elements are made of atoms. Atoms of the same element are alike. Atoms of different elements are different.

Elements In 1813, a system of representing elements with symbols was introduced. Each symbol consists of one or two letters. Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.

Common Elements Aluminum Al Bromine Br Calcium Ca Carbon C Gold Au Helium He Hydrogen H Nitrogen N

Compounds Compounds are also pure substances. But compounds are made from more than one element. Water is a compound. Water can be broken down into simpler substances – hydrogen and oxygen. (heat)

Element, Compound, or Mixture? Rocks

Element, Compound, or Mixture? Rocks

Element, Compound, or Mixture? Copper

Element, Compound, or Mixture? Copper Cu

Element, Compound, or Mixture? Jelly Beans

Element, Compound, or Mixture? Jelly Beans

Element, Compound, or Mixture? Table Sugar

Element, Compound, or Mixture? Table Sugar C12H22O11

Element, Compound, or Mixture? Diamond

Element, Compound, or Mixture? Diamond C

Element, Compound, or Mixture? Tea

Element, Compound, or Mixture? Tea

Element, Compound, or Mixture? Salt

Element, Compound, or Mixture? Salt NaCl

Element, Compound, or Mixture? Neon Gas

Element, Compound, or Mixture? Neon Gas Ne

Element, Compound, or Mixture? Salad

Element, Compound, or Mixture? Salad

Element, Compound, or Mixture? Pure Water

Element, Compound, or Mixture? Pure Water H2O

Element, Compound, or Mixture? Aluminum

Element, Compound, or Mixture? Aluminum Al

Element, Compound, or Mixture? Lemonade

Element, Compound, or Mixture? Lemonade

Element, Compound, or Mixture? Silver

Element, Compound, or Mixture? Silver Ag

Element, Compound, or Mixture? Sand

Element, Compound, or Mixture? Sand

Exit Ticket The number of what component of an atom determines which type of element it is? What is the main difference between a compound and a mixture? List some ways or tools that can be used to separate mixtures