Physical & Chemical Changes Chapter 3 Physical & Chemical Changes

Properties of Matter Physical Properties are characteristics of a substance that can be observed without changing the identity of the substance. Ex. Wood is wood whether it is in a house, a toothpick or a baseball bat. Physical Properties that you already learned about: Mass Volume Density Weight Also, color, texture, hardness, shape, etc.

Section 1 - Another Important Physical Property of Matter that we need to study is the… Phases of Matter There are 4 phases of matter: Solid Liquid Gas Plasma

Section 1 - Solids Have a definite shape and a definite volume Particles (molecules) are packed very close together so no movement can occur except vibrations. 2 types Crystalline solids have particles arranged in regular repeating patterns, ex table salt, quartz Amorphous solids have particles that aren’t arranged in a rigid way, so they can flow slowly, ex – candle wax, silicone rubber.

Section 1 - Liquids Do not have definite shape, but do have a definite volume Particles are close together, but not as close together as a solid. The particles can move past one another, thus allowing it to flow. They take the shape of the container they are in. One important Property of liquids is viscosity Viscosity – the resistance of a liquid to flow; ex honey has a higher viscosity than water.

Do not have definite shapes or volumes. Section 1 - Gases Do not have definite shapes or volumes. Particles are very far apart and move very freely.

NOTE: Plasma TV’s ARE NOT made of Plasma!!!! Section 1 - Plasma Extremely high in energy and temperature. Matter becomes so hot that the electrons separate from the nucleus. Plasma is rare on earth (ex. lightning & parts of flames), but is the most common form of matter in the universe because…. Stars are made of plasma and stars are quite common. NOTE: Plasma TV’s ARE NOT made of Plasma!!!!

Section 1 – More About Gases 2 scientists studied how gases behave in relation to pressure and temperature. Boyle’s Law – pressure & volume are inversely (indirectly) related The higher the pressure, the lower the volume. The lower the pressure, the higher the volume Charles’ Law – temperature & volume are directly related The higher the temperature, the higher the volume The lower the temperature, the lower the volume

Section 1 – Gas Laws Boyle’s Law – pressure & volume are inversely (indirectly) related P1 = V2 P2 V1 Charles’ Law – temperature & volume are directly related V1 = V2 T1 T2

Section 1 – Using the Gas Laws If 50 mL of oxygen gas is compressed from 20 atm of pressure to 40 atm of pressure, what is the new volume? (assume constant temp) GIVEN: V1 = 50 mL V2=? P1 = 20 atm P2 = 40 atm WORK: P1 = V2 P2 V1 20 atm = V2 40 atm 50 mL 1000 atm mL = 40 atm (V2) 40 atm 40 atm V2 = 25 mL

Section 1 - Using the Gas Laws A gas occupies a volume of 100 mL at 300° C. At what temperature will the gas have a volume of 200 mL? GIVEN: V1 = 100 mL V2= 200 mL T1 = 300° C T2 = ? WORK: V1 = V2 T1 T2 100 mL = 200 mL 300° C T2 100 mL (T2) = 60,000° C mL 100 mL 100 mL T2 = 600° C

Section 2 - Phase Changes Phase changes are caused by adding or taking away thermal energy Thermal energy is fancy schmancy word for HEAT!!!!!! Phase changes of matter are called: Melting Freezing Vaporization Condensation Sublimation

Section 2 - Phase Changes cont’d Phase changes are Physical Changes This is because the substance is changes its form, but it is not changing the kind of substance it is chemically. Ex – water (H2O) is still water whether it is in an ice cube, liquid water or water vapor)

Section 2 - Solid – Liquid Phase Changes Melting - Solid to Liquid Melting point – temperature at which a substance will melt Freezing – Liquid to Solid Freezing Point – temperature at which a substance will freeze. The melting point of a substance is the same temperature as its freezing point!!

Section 2 - Liquid - Gas Phase Changes Vaporization – Liquid to Gas 2 kinds: Evaporation – Liquid to Gas only at the surface of liquid Boiling – Liquid to Gas in the entire liquid Temperature at which a substance boils is the boiling point

Section 2 - Gas - Liquid Phase Changes Condensation – Gas to Liquid The gas molecules lose thermal energy (heat) and slow down. Then, as they come together, they join to form a liquid.

Section 2 - Solid - Gas Phase Changes Sublimation – Solid directly to Gas Examples Solid carbon dioxide (dry ice) changes directly into a gas Moth balls

As you move to the right, is heat being added to or given off by the substance?

As you move to the right, what is happening to the space between the molecules?

As you move to the left, is heat being added to or given off by the substance?

As you move to the left, what is happening to the space between the molecules?

What temperature is this if this substance is water?

What temperature is this if this substance is water?

Let’s Review for a Moment… Phase of matter, color, shape, hardness, mass, volume, density were all what kind of properties of matter? PHYSICAL PROPERTIES!!! Right……

Section 3 - Physical Properties - Definition Physical Properties – properties of matter that can be observed using the senses without changing the identity of a substance. What kind of property would describe a change of matter into another substance?

Section 3 - Chemical Properties and Changes Chemical Properties – the properties that describe the ability of a substance to change into a different substance. Flammability – the ability to burn Ex wood is flammable Supporting burning – the ability of a substance to be used during burning. Ex – oxygen is needed for wood to burn but the oxygen itself doesn’t burn.

Section 3 - Chemical Properties and Changes Chemical changes (aka chemical reaction) – the process by which a substance changes into another substance by chemical means. Ex: cars rusting, wood burning, yeast changing sugar into gas in bread, cheese aging, leaves changing color…

Classify the following as either a physical or chemical change…. An ice cube cracking Carving a piece of marble into a statue Burning wood Wax melting Sugar dissolving in tea or coffee Pop rocks releasing carbon dioxide into your mouth Leaves changing colors in the fall