Properties of Matter - Vista Unified School District

Transcript Properties of Matter - Vista Unified School District

Unit 2: Matter and Change

OBJECTIVES

Students will be able to: 1. define matter 2. describe the states of matter (solid, liquid, gas) 3. identify the characteristics of of a substance, element and compound 4. distinguish between physical and chemical change 5. identify properties of matter (chemical, physical, intensive, extensive) 6. identify changes in matter that occur (physical and chemical change) 7. explain the law of conservation of mass

WHAT IS MATTER?

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

– gold – sound – sunlight – air QuickTime™ and a decompressor are needed to see this picture.

– 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

STATES OF MATTER

Shape Volume Arrangement of particles Attraction between particles Takes the shape of container Fills volume of container Random, far apart Essentially none Takes the shape of container Definite volume Definite shape Definite Volume Random, close Strong Fixed, close Very strong

GAS vs. VAPOR • Gases and vapors are similar, but terms should not be used interchangeably

–

Gas

refers to a substance that is naturally in the gaseous state at room temperature: hydrogen gas –

Vapor

refers to the gaseous state of a substance that is a solid or a liquid at room temperature: water vapor

THE PHASES OF WATER

solid liquid gas

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

(PURE) SUBSTANCE

• 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 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.

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

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

may

change or react to form other substances – 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 QuickTime™ and a decompressor are needed to see this picture.

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.

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.

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

THE LAW OF CONSERVATION OF MASS • Mass (matter) is neither created nor destroyed during a reaction…

mass is conserved:

Mass

reactants

= Mass

products

2HgO 216 g

reactants   

2Hg + O 200 g + 16 g