8th grade Physical ScienceCST Review

The year in a Nutshell!

Standard 1: Motion and Speed

•A. The position of an object is defined in relation to a reference point. Ex: A plane flying across a mountain- the mountain is the reference point.•B. S = D/T T= D/S D= T X S•C. Velocity is SPEED with DIRECTION,•D. Speed v Time graph- If the line slants up it shows the object is speeding up, horizontal line means constant speed and slants down means slowing down.

Reference point –object that appears to stay in place – compare for measuring motion

Motion – when an object changes position over time when compared with a reference point

Speed - the amount of distance traveled in a certain amount of timeEx. meters per second, miles per hour

Problems - divide the distance an object travels by the time it takes

V=D=

T=

VT

D

D

T

V

Standard 1: Motion and SpeedAverage speed – the speed of an object over a period of time A graph of average speed (or constant speed) will always be a straight line!

Velocity - is a measure of both speed and direction of motionAny change in speed or direction changes velocity.Acceleration - the rate at which velocity changes.

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11

Time

Distance

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11

Time

Speed

Pay attention to X and Y axes!

Increasing speed (Constant acceleration) Decreasing speed (Negative acceleration)Time

Speed

Standard 2: FORCES

•A. Forces have both magnitude (size) and direction.•B. When and object has two or more forces acting on it at once, the result motion is in one direction. •C. When the forces on an object are BALANCED the motion DOES NOT change. When the forces on an object are UNBALANCED the motion DOES change its velocity meaning it will speed up, slow down or change directions. •D. The greater the mass of the object the more force is needed to achieve the same rate of change in motion. •E. Gravity helps form the shape of planets, stars and the solar system.

Force – Any push or pull affecting matter. Forces make changes in velocity happen.

All forces have – direction and magnitude (size)

• When two forces are exerted on an object in the same direction, their magnitude is added – in opposite directions their magnitude is subtracted - giving net force.

35 newtons to the right

1oo N 1oo N 1oo N 1oo N

Net Force= 4oo N left

1oo N 15o N

Net Force= 50 N right

Standard 2: FORCES

• Balanced Forces – motion does not change – sitting still or keeping the same motion

• Unbalanced forces – cause change in velocity – speed up, slow down, change direction, etc.

• Elastic forces – counteract other forces.– Compression – prevents crushing– Tension - prevents stretching/snapping

Compression in chair legs – stops weight from moving down

Gravity

Tension in cables – stops Bridge from falling

Gravity

Balanced Forces

Standard 2: FORCES• Gravity – force affecting all matter – depends on mass and distance

between objects. More mass = more gravity.– Forms the spherical shape of planets and stars, forms the shape of

orbits. • Greater mass = greater force needed to make motion change.

More mass = greater attraction

Less distance = greater attraction

Standard 3: Matter

•A. Atoms are composed of protons (+) neutrons (0) and electrons (-). Protons and Neutron make up the nucleus (atomic mass) and the electrons are in the electron cloud. •B. Compounds are form by combining two or more elements. Compounds have properties that are different than their elements that make them up.•C. Atoms and molecules form solids by building up repeating patterns.•D. The three states of matter are solid, liquid and gas. The molecular motion of a solid is low, liquid is medium and gas is fast. •E. In solids the atoms are closely locked in position and can only vibrate. In liquids the atoms are always in contact but move past one another. In gases the atoms are free to move independently but collide frequently. •F. Elements make up compounds. Elements are found on the periodic table.

Standard 3: Matter

Pure substances – Elements

-Are made up of ONE type of particle –all of the particles are the same

– They cannot be broken down into anything simpler by physical means.– All elements can be found on the periodic table.– Ex. oxygen, water, etc.

*An element is a pure substance that cannot be separated into simpler substances by physical or chemical means

*A compound is a pure substance composed of 2 or more elements that are chemically combined. Compounds have properties that are different from their individual elements.

Standard 3: MatterAn Atom is composed of protons and neutrons in the

nucleus, and electrons outside the nucleus.

Nucleus- made up

of protons and

neutrons.

electron cloud- where electrons are

found

The atomic number is equal to the number of protons and electrons in an atom. This tells you what element it is!

Atoms with the same number of protons, but different numbers of neutrons are called isotopes.

• Solid: The particles just sit in place and vibrate; low molecular motion

• Liquid: The particles overcome some of their attraction and slide past each other – like the ball-pit in the McDonalds playground; medium molecular motion

• Gas: The particles have almost no attraction and move very quickly and independently of each other – like a room full of superballs bouncing all over the place! Fast molecular motion

Standard 3: Matter

*The states of matter (solid, liquid, gas) depend on molecular motion.

SOLID LIQUID GAS

Standard 4: Astronomy

•A. Galaxies are clusters of billions of stars and have different shapes.•B. The sun is a star in the Milky Way. Stars differ in size, temperature, and color. •C. AU measures distances within the solar system. Light Years measures distances outside the solar system. •D. Stars are the source of light for all bright objects in space. The moon, planets and other objects shine by reflected light from the sun, not by their own light. •E. There are 8 planets in the solar system. Terrestrial (Rocky) planets are Mercury, Venus, Earth and Mars. Gas Giants are Jupiter, Saturn, Uranus and Neptune.

Mercury is the closest planet to the sun, has very drastic temperature differences, and closely resembles Earth’s moon

Venus rotates in the opposite direction than Earth does, and is the hottest planet in the solar system

Standard 4: Astronomy

INNER PLANETSThese planets are closest to the sun

and are small dense and rocky

Earth can support life because it has liquid water. Mars is known as the “red planet,” has a very thin atmosphere and low pressure.

Jupiter is mostly made of H & He and is the largest planet.The Great Red Spot is a storm about 1.5 times the size of Earth.

Saturn is the 2nd largest planet in the solar system and has the largest rings of all of the planets that consist of icy particles.

Standard 4: Astronomy

OUTER PLANETSThese planets are all very large gas giants with no known solid surfaces

Uranus is tipped over on its side and rotates in a direction opposite of the Earth.

Neptune is the outermost planet and contains belts of clouds.

Standard 4: Astronomy

*Comets are made mostly of ice & dust, revolve around the sun in an ellipse, and are about the size of an Earth mountain.

*Asteroids are rocky bodies that orbit around the sun but are too small to be considered a planet (most are < 1 kilometer)

*Our sun is an average sized star. Stars may differ in size, temperature, and color. It is located between the center and the edge of the MW, along a spiral arm.

*Galaxies are clusters of billions of stars, and may have different shapes. Our

Milky Way Galaxy is a spiral galaxy.

*Stars are the source of light for all bright objects in outer space. We can see objects in our solar system from reflected sunlight.

* A light-year is the distance light travels in 1 year; used to measure distances outside the solar system. An astronomical unit (AU) is the average distance between the Earth and the sun; used to measure distances inside the solar system.

Standard 5:

•A. Reactants interact to form products with different chemical properties. •B. Conservation of Mass- whatever number of atoms you start with in an equation you must end up with in the product. This is where balancing comes in. •C. Chemical Reactions are either endothermic (COLD) when heat is absorbed or exothermic (HOT) when heat is released. •D. Physical process includes change of state- melting, freezing, condensation, evaporation and sublimation. Material changes form with NO chemical reaction. •E. Acids have a pH from 1-6.9.•F. Neutral solutions have a pH of 7.•G. Bases have a pH from 7.1- 14.

Standard 5: Chemical Reactions

• Chemical reactions have 2 parts, the reactants and the products

Na + Cl NaCl

Reactants

Products

* Products will have DIFFERENT properties than the reactants.

* The Law of Conservation of Matter states that matter cannot be created or destroyed. In chemical reactions this means the reactants must equal the products.

H2 + O2 H2O . . .Not correct

2H2 + O2 2H2O . . .Correct

*Chemical reactions usually release (exothermic) or absorb (endothermic) heat.

Standard 5: Chemical Reactions • Physical changes don’t change the identity of the

substance, where chemical changes do change the identity

• Changes of state are examples of physical changes!

Condensing B

oilin

gF

reezing

Mel

ting

ACIDSpH < 7Taste sourTurn blue litmus paper red

BASESpH > 7Taste BitterTurn red litmus paper blue

Neutral solutions have a pH of 7

Standard 5: Chemical Reactions

Standard 6: Chemistry of Living Systems

•A. Carbon has the ability to combine in many ways with itself to form chains. It is the backbone of many compounds. Carbon can form 4 bonds. The bonds formed in living things are always covalent. •B. Living organisms are made mostly of the elements CHNOPS- carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. •C. Living organisms can be made with small molecules such as water and salt and very large ones such as carbs, fats, proteins, and DNA.

Standard 6: Organic Chemistry

*Carbon is the main element in living organisms. It can bond with itself to form chains. Long chains of carbon make polymers. Carbon can form up to 4 bonds. They can form single, double, or triple COVALENT BONDS.

*Living organisms are made mostly of the elements carbon, hydrogen, nitrogen, oxygen, phosphorus, & sulfur (CHNOPS)

*Living organisms can be made with small molecules such as water and salt, and very large ones such as carbohydrates, fats, proteins, and DNA.

* Carbon forms double bonds (=) and single bonds (---) below.

H Cl

C = C

H H

Standard 7: Periodic Table

• A. Metals make up most of the periodic table. The most reactive elements are on the left side of the PT. As you move across the PT they get less reactive. Noble gas or inert gases are found in group 18.

•B. The atomic number tells you the number of protons and electrons. You find the number of neutrons by subtracting the atomic number from the atomic mass. Row #s tell you the number of shells an atom has and the group number tells you the number of valence electrons. •C. Each isotope of the element has a different number of neutrons in the nucleus. •D. Substances can be classified by their properties- melting point, boiling point, density, hardness, etc.

Standard 7: Periodic Table

• Metals (green): shiny, malleable, good conductors, high melting point.

• Nonmetals (yellow): dull, poor conductors, brittle solids or gases

• Metalloids (blue): properties of both metals and nonmetals.

Standard 7: Periodic Table

• Metals make up most of the periodic table.• Metals are the most REACTIVE elements. As you

move left to right across the PT they get less reactive.

• The Noble gases(Inert gases) are found in group 18 and do not react with any other elements on the PT.

• Rows tell you the number of shells an atom has.• Groups tell you the number of valence electrons.

Standard 8: Density and Buoyancy

•A. Density is mass per unit volume. D = M/V•B. You find the volume of regular objects by multiply l x w x h. •C. You find the volume of irregular objects by using water displacement. •D. The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced. •E. If the BF>W the object will FLOAT. If the BF< W the object will SINK.

• Density - mass per unit volume – how much matter is stuffed into a space.

• Density = mass divided by volume

• g/cm3 or g/ml (mass per volume)

• Water – density of 1 g/ml. Objects with a greater density than 1 will sink, density less than 1 will float.

• Wood – density 0.78 g/cm3

• Copper – density 8.92 g/cm3

Steel Styrofoam

Volume (space) is the Same – 1cm3. Steel is heavier, so it is denser.

Mass = 7.85 g Mass = 0.1 g

Standard 8:Density/Buoyancy• Buoyant force is equal to the weight of the volume of the

fluid displaced by the object. • Archimedes’ principle • Volume in the fluid determines buoyant force

• If the BF > than the W, the object will FLOAT.• If the BF < than the W, the object will SINK.

Questions

Standard 9:The Scientific Method• Steps that scientists use to answer questions and solve

problems

1. State The Problem

2. Form a Hypothesis - A possible explanation or answer to a question – testable

3. Perform an Experiment

Experiment has a control group and an experimental group - change only one factor – the independent variable (x-axis). You are looking for an effect to happen - the dependent variable (y-axis). – Experimental Group - Has the variable– Control Group – No Variable

4. Analyze Data

5. Form a conclusion - Did your results support your hypothesis or not?

Answers!