Describing Matter: Physical and Chemical Properties EQ: What is matter and how can its properties be described?

Matter O You have probably heard the word matter many times. O As a matter of fact… O Hey, what’s the matter? O In science, matter has a specific meaning. O Matter is anything that has mass and occupies space.

Matter O Everything around you is matter O The tables O The person sitting next to you O Your pencil O The air you are breathing

Matter O Even though the table you are sitting at and the air you are breathing are both matter, nobody has to tell you they are composed of different materials.

Matter O Matter can have many different properties or characteristics. O Materials can be rough or smooth, hot or cold, liquid, solid or gas. O Some materials catch fire easily, others do not. O Chemistry is the study of the properties of matter and how matter changes.

Properties of Matter O The properties of matter and changes to matter depends on its (the matter’s) makeup. O Some types of matter are substances and some are not.

Substances O In chemistry, a pure substance is a single kind of matter that is pure, meaning it has a specific makeup, or composition, and a specific set of properties. O For example, table salt has the same composition and properties no matter where it comes from, be it a mine or seawater.

Substances O On the other hand, consider blueberry muffin batter. O Some of the ingredients like sugar and salt are pure substances, the batter itself is not. O It consists of several ingredients that can vary with the recipe

Substances Pure Substances Not Substances O Table salt O Table sugar O Baking soda O Elements and compounds O Why are they pure substances? O Flour O Baking powder O Eggs O Milk O Fruit O Mixtures and solutions O Why are they not substances?

Properties of Matter O Every form of matter has two kinds of properties: O Physical properties: O Chemical properties: O A physical property of oxygen is that it is a gas at room temperature O A chemical property of oxygen is that it reacts with iron to form rust.

Physical Properties of Matter O A physical property of matter is a characteristic of a pure substance that can be observed without changing it into another substance.

Physical Properties of Matter O A physical property of water is that it freezes at 0*C (32*F) O When liquid water freezes into solid water, it’s still water, it’s just changed into another state of matter.

Physical Properties of Matter O Other examples of physical properties of matter: O Texture (I could change the texture of my hair to stick straight and it would still be hair) O Color (I could change the color of my hair and it would still be hair) O Flexibility (I could bend a piece of paper and it would still be paper or I could snap a stick in two and it would still be a stick (or 2 sticks!)) O Ability to dissolve (sugar dissolves in tea, but it’s still sugar in tea) O Magnetism (iron is magnetic, but it’s still metal, copper is not magnetic, but its still a metal) O Adjectives!

Chemical Properties of Matter O A chemical property is a characteristic of a pure substance that describes its ability to change into another substance. O To observe the chemical properties of a substance, you must try to change it into another substance first

Chemical Properties of Matter O For example, a chemical property of natural gas (methane) is that is can catch fire and burn in the air. O When it burns, it combines with oxygen and forms new substances: water and carbon dioxide. O Burning is a chemical property of natural gas as well as wood and gasoline

Chemical Properties of Matter O Other chemical properties of matter: O Rusting: iron combined with oxygen in the air O Tarnishing: Silver combines with sulfur in the air O Rising: yeast combines with bread dough and air O Verbs!

Describing Matter: Measurement Unit 2: Eighth Grade EQ: What is matter and how is it described?

Measurements O Another way to describe matter is by its (the matter’s) measurements. O There are all sorts of ways to measure matter, and we use these measurements every day. O To measure matter, we consider its weight/mass, volume, density

Measurements Mass Weight O The amount of matter in an object O Does not change with location O Physical property O Described as kilograms, or pounds O The measure of the force of gravity on you. O Changes by location O Physical property O Described in newtons (N)

Measurements/Volume O Volume is the amount of space that matter occupies. O Amount of space air takes up in a balloon O Amount of space a brick takes up in a wall O The amount of space Coca-Cola takes up in a bottle. O Volume = L X W X H O Submerge in water for irregularly shaped objects

Measurements/Density O Which weighs more: a pound of feathers or a pound of bricks? O Neither! They both weigh a pound O A pound of feathers takes up more space than a pound of bricks, because bricks are denser. O The mass of a material in a given volume O It’s thickness O Density = Mass/Volume

Describing Matter: Composition – Elements, Atoms and Molecules Unit 2: Eighth Grade EQ: What is matter and how can its properties be described?

Elements O What is matter made of? O What makes one kind of matter different from another kind of matter?

Elements O Early Greeks proposed that all matter was made of different combinations of four “elements” O Earth O Wind O Fire O Water O This idea held for over 2,000 years

Elements O Now scientists know that all matter in the universe is made of slightly more than 100 elements O An element is a pure substance that cannot be broken down into any other substance by physical or chemical means.

Elements O Elements are the simplest substances. O Each element can be identified by its specific physical and chemical properties.

Elements O We are very familiar with elements: O Aluminum: foil, lawn chairs O Zinc: pennies (which are coated with copper, another element)

Elements O What is the smallest possible piece of matter? O Could you keep tearing a piece of aluminum foil to a point where you have the smallest piece possible? O The answer is yes

Atoms O Since the early 1800’s we have known that all matter is made of atoms. O Atoms are the basic particle from which all elements are made.

Atoms O Different elements have different properties because their atoms are different. O Atoms can be further broken down into smaller parts: O Electrons O Nucleus O Protons O Neutrons

Molecules O Atoms have the ability to combine, or join up with other atoms. O When atoms combine, they form a chemical bond. O In many cases, atoms combine to form molecules

Molecules O Molecules are groups of two or more atoms held together by chemical bonds. O Single atoms of elements are not molecules. O A molecule of water is one oxygen atom chemically bonded to two hydrogen atoms O H20

Molecules O Other examples O Two chemically bonded oxygen atoms O O2 O Oxygen O One carbon atom chemically bonded to two oxygen atoms O CO2 O Carbon dioxide O the-science-guy-atoms-and-molecules-full- episode the-science-guy-atoms-and-molecules-full- episode

Describing Matter: Composition --- Compounds and Mixtures Unit 2: Eighth Grade EQ: What is matter and how can it be described?

Compounds O All matter is made of atoms O But most elements in nature are found combined with other elements. O A compound is a pure substance made of two or more elements chemically combined in a set ratio.

Compounds O A compound may be represented by a chemical formula. O The formula shows the elements in the compound and the ratio of atoms. O Example: Carbon dioxide

Compounds O Our waste gas is carbon dioxide. O Its chemical formula is CO 2 O The “2” below the “O” for oxygen tells you that the ratio of carbon to oxygen is 1 to 2 O Meaning for the compound to be carbon dioxide, you must have 1 carbon atom chemically bonded to 2 oxygen atoms O If there is no number next to (below) after an element’s symbol the number “1” is understood

Compounds O CO = Carbon Monoxide O Carbon atoms: O1O1 O Oxygen atoms O1O1 O C 12 H = Table sugar O Carbon atoms O 12 O Hydrogen atoms O 22 O Oxygen atoms O 11

Compounds O When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements.

Compounds O C 12 H 22 O 11 = table sugar O Made of carbon, hydrogen, and oxygen. O The sugar crystals do not resemble the gases oxygen and hydrogen or the black carbon you see in charcoal. O When the elements chemically combine, they form new properties

What is a mixture? O I have provided a cup of objects. O As a group, examine the objects, then sort them into at least three groups. Each item should be grouped with similar items O Describe the differences between the groups. O Make a list of the characteristics of each sorted group.

Mixtures O Elements and compounds are pure substances, but most materials you see every day are not. O Most are mixtures

Mixtures O A mixture is made of two or more substances --- elements, compounds or both– that are together in the same place but are not chemically combined.

Mixtures O Mixtures are different from compounds in two ways: O 1) Each substance keeps its individual properties O 2) The parts of a mixture are not combined in a set ratio.

Mixtures O If you look at soil up close, you will see bits of sand, silt, clay, and humus. O They are not chemically combined O Each part keeps its own properties O There is no set ratio O A sample of soil from another place will not contain the same amount of sand, silt, clay and humus

Mixtures O A mixture can be described at heterogeneous or homogenous.

Mixtures Heterogeneous Homogeneous O You can see the different parts. O Soil O Salad – lettuce, tomatoes, cucumbers, croutons, etc O The substances are so even you cannot see the different parts O Sweet tea – sugar dissolves, and you cannot see the crystals. O This is called a solution O Air is a solution O Nitrogen (N 2 ) + Oxygen (0 2 )+other gases

Separating Compounds and Mixtures O Compounds and mixtures differ in another way. O A compound can be difficult to separate. O A mixture is easy to separate