Unit 1: Matter and Change

Review

1. Organize the following terms into a logical • • • • • • • flowchart/concept map element • • brass matter • • pure substances gravel • • seawater • homogenous mixture/solution oxygen gas (O 2 ) sodium chloride (NaCl) heterogeneous mixture mixtures compounds iron air

Review

• • • • • 2. Identify each of the following statements as describing either a physical property or a chemical property Water boils below 100  C on top of a mountain.

Oxygen gas supports combustion.

Lead is denser than aluminum.

Sugar tastes sweet.

Fertilizers help to increase agricultural production.

Matter

Anything that has mass and takes up space

Pure Substance

Matter with an unique and unchanging composition physical change

Mixtures

A combination of 2 or more pure substances

Element

Pure substance that cannot be broken into more simpler substances chemical change

Compound

Atoms of two or more elements that are chemically united in a fixed proportion

Homogeneous Mixture/Solutio n

Mixture with a uniform composition

Heterogeneo us Mixture

Mixture does not appear to be the same throughout

What is matter?

• Anything that takes up space and has mass • Matter or not?

– gold – sound – sunlight – air – water – heat – thoughts

Mass & Weight

• Mass is the measure of the amount of matter that makes up an object • Weight is a measure of the force of gravity on an object – weight = mass x gravity – weight varies depending on distance from the earth’s surface • Because the value never changes, scientists use mass, not weight to measure matter

(Pure) Substances

• A substance is a form of matter with an unique and unchanging composition (composition doesn’t change from sample to sample) • Examples: Water, salt • What about salt water?

• All pure substances are either elements or compounds

Element

• An element is a pure substance that cannot be broken into more simpler substances • Examples: gold (Au), oxygen (O 2 ) • To date, there are 118 elements QuickTime™ and a decompressor are needed to see this picture.

Compounds

• Compounds are substances composed of atoms of two or more different elements that are chemically united in a fixed proportion – Water (H 2 O), sugar (sucrose, C 12 H 22 O 11 ), ammonia (NH 3 ) • Compounds can be separated back into its elements (by chemical means) – Electrolysis of water: • 2H 2 O  2H 2 + O 2 QuickTime™ and a decompressor are needed to see this picture.

Matter

Anything that has mass and takes up space

Pure Substance

Matter with an unique and unchanging composition physical change

Mixtures

A combination of 2 or more pure substances

Element

Pure substance that cannot be broken into more simpler substances chemical change

Compound

Atoms of two or more elements that are chemically united in a fixed proportion

Homogeneous Mixture/Solutio n

Mixture with a uniform composition

Heterogeneo us Mixture

Mixture does not appear to be the same throughout

What is a mixture?

• A mixture is a combination of two or more pure substances – the composition of a mixture can vary – Substances in mixtures are physically but not chemically combined – each pure substance retains its individual chemical properties – Air is mostly a mixture of nitrogen, oxygen,and argon • There are two types of mixtures: – Heterogeneous and homogeneous QuickTime™ and a decompressor are needed to see this picture.

QuickTime™ and a decompressor are needed to see this picture.

QuickTime™ and a decompressor are needed to see this picture.

Heterogeneous Mixture

• Heterogeneous mixtures do not appear to be the same throughout and individual substances remain distinct • Example: Trail mix

Homogeneous Mixture/Solutions

A homogeneous mixture has a uniform composition throughout – it always has a single phase (solid, liquid or gas) • Homogeneous mixtures are also called

solutions

• All solutions contain a solute and a solvent – solute is the substance present in smaller quantity – solvent is the substance present in greater quantity

Examples of Solutions

solution phase solute solvent

Air gas-gas oxygen, argon other gases Carbonated water liquid-gas carbon dioxide (CO 2 ) Vinegar liquid-liquid acetic acid nitrogen water water Brass solid-solid zinc copper

Properties of Matter

• Every pure substance has a unique set of properties • A property is a characteristic that allows us to recognize a certain type of matter Physical properties of water clear liquid at room temperature boils at 100 o C freezes at 0 o C density at 4 o C is 1.000 g/cm 3

Physical properties

• Physical properties are those properties that can be measured without changing the identity of the substance: – color, odor, melting point, boiling point, density, hardness, taste • Physical properties are either

extensive

or

intensive

Extensive property Intensive property

•A property that depends on the amount of a substance present •Example: Mass, volume, length •value will change when the amount of substance changes: 1 mL of water has a mass of 1 g while the mass of 1 L has a mass of 1000 g •A property that is independent of the amount of substance present •Example: Density, boiling point, melting Point •value will not change when the amount of substance changes: The density of water is always 1.00 g/mL

Chemical Properties

• Chemical properties describe the way a substance substances

may

change or react to form other – Corrosion, flammability • The

inability

of a substance to change is also a chemical property – Argon gas is inert • To observe a chemical property a chemical change must occur

Properties of Copper

Physical properties reddish brown, shiny good conductor of heat Chemical properties Forms a green copper carbonate compound when in contact with moist air Forms new substances when combined with nitric & sulfuric acid Density = 8.92 g/cm 3 Melting point = 1085 o C Forms deep blue solution when in contact with ammonia Boiling Point = 2570 o C

Changes in Matter

• A physical change is a change that alters the appearance of the substance drastically but leaves its composition unchanged: – bend, grind, split, crush, boil, freeze, melt, vaporize

Chemical Change (Chemical Reaction)

• In a chemical change a substance is transformed into a chemically different substance – When hydrogen burns in air it reacts with oxygen to form water • The new substances formed have different compositions and different properties • Terms: Explode, rust, oxidize, corrode, tarnish, ferment, burn, rot etc.

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Evidence of Chemical Change

• Formation of a gas or solid • Color change • Energy change • odor

Physical or chemical change?

• Plants use carbon dioxide and water to make sugar.

• On a cold day, water vapor in the air forms frost.

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