Review for Physical Science Exam

Grade 8

Types of Measurements1. Length a. The distance from one point to another point. b. Base unit is the meter (m).

c. Tool is the metric ruler.2. Volume a. The amount of space a substance occupies. b. Base unit is the liter (L). c. Tools: metric ruler for regular solids or graduated cylinder for liquids.

3. Mass a. The amount of matter in a substance. b. Base unit - kilogram (kg).

c. Tool is the balance.4. Weight a. A measure of gravitational force on an object. b. Unit is the newton (N). c. Tool is the scale.

5. Time a. How long an event takes to occur. b. Unit is the second (s). c. Tool is the clock (stopwatch).6. Temperature a. The amount of kinetic energy a substance has. b. SI unit is the Kelvin (K). c. Tool is the thermometer.

7. Density

a. How compacted the matter is in a substance.

b. Units can be g/mL, g/cm3, kg/m3.

c. Density is a derived unit (it is made up of other types of measurement).

d. D = m / v

e. Objects float if their density is less than the density of the fluid they are in.

7. Density

a. How compacted the matter is in a substance.

b. Units can be g/mL, g/cm3, kg/m3.

c. Density is a derived unit (it is made up of other types of measurement).

d. D = m / v

e. Objects float if their density is less than the density of the fluid they are in.

Scientific Experimentation

controlled experiment

-Only one variable should be changed

Manipulated (independent) – changed by the experimenter.Responding (dependent) – the effect.

Matter

Matter = any material substance with Mass & Volume

CLASSIFICATION OF MATTER

The Organization of Matter

Matter

MixturesPure Substances

Heterogeneous Homogeneous

CompoundsElements

Matter

Solid

Liquid

Gas

comes in 3 phases

Solid

Definite Shape

Definite Volume

Liquid

Indefinite Shape – takes the shape of the container

Definite Volume

Gas

Indefinite Shape – takes the shape of the container

Indefinite Volume – can expand and be compressed

Plasma

• Plasma: a high energy gaseous state of matter.• It is very unstable.• Particles are moving extremely fast, free energy• Most abundant phase of matter• Only present under extremely hot/energetic situations

• Example: Sun

• Plasma: a high energy gaseous state of matter.• It is very unstable.• Particles are moving extremely fast, free energy• Most abundant phase of matter• Only present under extremely hot/energetic situations

Example: Sun

Plasma

CHANGES IN STATE

• Melting: Solid to liquid• Boiling: Liquid to gas• Sublimation: Solid to gas

– The above three require input of energy

• Condensation: Gas to liquid• Freezing: Liquid to solid• Deposition: Gas to solid

– The above three release energy

Law vs. Theory

• S: Develop a law– Law: Summarizes the outcome of several experiments

that occur repeatedly and consistently.

– Example: The spoiled food served at lunch makes people sick with a stomachache.

• Step 5: Develop a theory– Theory: Explanation for why a law exists.

– Example: It is the bacteria in the spoiled food that makes people ill.

ELEMENTS

• contain only one type of atom• building blocks of matter• 115 known elements today, 90 which occur

naturally• Found on periodic table

– The first letter is always capitalized, the second letter is always lower case

• Fluorine is F, not f

• Cobalt is Co, not CO (which is carbon monoxide)

Atom the smallest particle making up

elements

Drawing an Atom of Carbon

C12.011

6

Atomic Mass

Atomic #

minus Atomic # = # of n0

= # of p+ and # of e-

Carbon has 6 p+ and 6 e-

Carbon has 6 n0

Drawing an Atom of Carbon

6 p+

6 n0

e-

e-

e- e-

e-

e-

Compounds

Compounds - 2 or more elements chemically

combined to form a new substance with

new properties Properties – The way a

chemical substance looks and behaves

PHYSICAL PROPERTIES

• Characterize the physical state and physical behavior of a substance

• Each substance has unique physical properties

• Examples– Sulfur appears as a yellow powder– The boiling point of water is 100 oC– Carbon monoxide is odorless

CHEMICAL PROPERTIES

• Describe ways pure substances behave when interacting with other pure substances.

• Examples– Iron reacts with oxygen to form rust.– Platinum does not react with oxygen at room

temperature.

•substance changes state but does not change its chemical composition

• (it has the same melting point, boiling point, chemical composition, etc.)

Examples:•water freezing into ice•cutting a piece of wood into smaller pieces

• Melting point• Boiling point• Vapor pressure• Color• State of matter

• Density • Electrical conductivity• Solubility• Adsorption to a

surface• Hardness

• Reaction with acids• Reaction with bases

• Reaction with other elements

• Decomposition into simpler substances

• Corrosion

• when a substance changes into something new.

• This occurs due to heating, chemical reaction, etc.

• You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (bubbles forming, mass changed, etc).

Review• Mixtures and Pure Substances

– A mixture has unlike parts and a composition that varies from sample to sample

– A heterogeneous mixture has physically distinct parts with different properties.

– A homogeneous mixture is the same throughout the sample

– Pure substances are substances with a fixed composition

– A physical change is a change that does not alter the identity of the matter.

– A chemical change is a change that does alter the identity of the matter.

– A compound is a pure substance that can be decomposed by a chemical change into simpler substances with a fixed mass ratio

– An element is a pure substance which cannot be broken down into anything simpler by either physical or chemical means.