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# 8 th Grade Science Review - PowerPoint PPT Presentation

8 th Grade Science Review. What We Have Learned This Year. Standard 1 Motion. The velocity of an object is the rate of change of its position. Standard 1 Motion. To determine if motion is occurring compare the object to a reference point. Speed= distance time

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## 8 th Grade Science Review

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What We Have Learned This Year

Standard 1Motion

The velocity of an object is the rate of change of its position.

Standard 1Motion
• To determine if motion is occurring compare the object to a reference point.
• Speed= distance

time

• Velocity shows speed and direction.
• Acceleration is a change in velocity (speed or direction).
Question 1

An athlete can run 9 kilometers in 1 hour. If the athlete runs at that same average speed for 30 minutes, how far will the athlete travel?

a. 18 kilometers

b. 9 kilometers

c. 4.5 kilometers

d. 3.3 kilometers

Question 2

How much time is required for a bicycle to travel a distance of 100m at an average speed of 2 m/s?

a. 0.02 s

b. 50 s

c. 100 s

d. 200 s

Question 3

Which of the following represents the velocity of a moving object?

a. 40

b. 40 m north

c. 40 m/s

d. 40 m/s north

Question 4

The graph shows the speed of a vehicle over time.

How far did the vehicle travel during the first two seconds?

a. 0.2

b. 5 m

c. 10 m

d. 20 m

Question 5

The graph shows how the position of an object changes over time.

What is the speed of the object during the time interval from 4 seconds to 10 seconds?

a. 2 m/s

b. 3 m/s

c. 8 m/s

d. 16 m/s

Standard 2Forces

Unbalanced forces cause changes in velocity.

Standard 2Forces
• A push or pull
• A force has magnitude and direction.
• When forces are unbalanced, the object will move.
• When forces are balanced an object will not move.
• The greater the mass of an object, the more force will be needed to move it.
Question 1

A force is acting on each of the objects.

What can be concluded about these forces?

a. They are the same because they point toward the objects.

b. They are the same because they have the same magnitude.

c. They are different because they have different magnitudes.

d. They are different because they have different directions.

Question 2

The students are pushing a cart as shown. The cart will move as if it were acted on by a single force with a magnitude of

a. 50 N

b. 150 N

c. 200 N

d. 350 N

Question 3

A ball is dropped from the top of a tall building. As the ball falls, the upward force of air resistance becomes equal to the downward pull of gravity. When these two forces become equal in magnitude, the ball will

a. flatten due to the forces.

b. fall at a constant speed.

c. continue to speed up.

d. slow to a stop.

Question 4

Four forces are acting on a box as shown. This box will increase in speed

a. downward and to the left.

b. downward and to the right.

c. upward and to the left.

d. upward and to the right.

Question 5

A force of 5 N is required to increase the speed of a box to a rate of 1.0 m/s to 3.0 m/s within 5 s along a level surface. What change would most likely require additional force to produce the same results?

a. reduce the mass of the box

b. increase the mass of the box

c. make the surfaces of the box smooth

d. make the surfaces of the floor smooth

Standard 3Structure of Matter

Elements have distinct properties and atomic structure. All matter is comprised of one or more of over 100 elements.

Standard 3Structure of Matter
• Atoms are composed of protons, neutrons, and electrons.
• Compounds are made of 2 or more elements.
• Solids, liquids, and gasses are determined by the motion of the atoms.
• The Periodic Table is used to identify elements in compounds.
Question 1

Which of the following best describes an atom?

a. protons and electrons grouped together in a random pattern

b. protons and electrons grouped together in an alternating pattern

c. a core of protons and neutrons surrounded by electrons

d. a core of electrons and neutrons surrounded by protons

Question 2

Which of the following is found farthest from the center of an atom?

a. nucleus

b. proton

c. neutron

d. electron

Question 3

When magnesium (Mg) metal is burned in the presence of oxygen (O2), magnesium oxide (MgO) is produced. The properties of magnesium oxide are different than the individual properties of magnesium and oxygen because magnesium oxide is

a. a solution.

b. a mixture.

c. a compound.

d. an element.

Question 4

Within a substance, atoms that collide frequently and move independently of one another are most likely in a

a. liquid.

b. solid.

c. gas.

d. crystal.

Question 5

What is the name of the indicated atom in the acetic acid molecule shown?

a. carbon

b. calcium

c. chromium

d. copper

Standard 4Earth in the Solar System

The structure and composition of the universe can be learned from the study of stars and galaxies, and their evolution.

Standard 4Earth in the Solar System
• Galaxies are clusters of billions of stars.
• The Sun is one of many stars in our Milky Way galaxy.
• Astronomical units and light years are used to measure distances in space.
• Stars are the source of all light.
Question 1

The galaxies pictured would best be classified as

a. symmetrical.

b. spiral.

c. irregular.

d. barred.

Question 2

A galaxy is best described as a cluster of

a. hundreds of stars.

b. thousands of stars.

c. millions of stars.

d. billions of stars.

Question 3

To express the distance between the Milky Way galaxy and other galaxies, the most appropriate unit of measurement is the

a. meter.

b. kilometer.

c. light-year.

d. astronomical unit.

Question 4

Which of the following sets contains only objects that shine as a result of reflected light?

a. moons, planets, and comets

b. moons, comets, and stars

c. planets, stars, and comets

d. planets, stars, and moons

Question 5

An object composed mainly of ice is orbiting the Sun in an elliptical path. This object is most likely

a. a planet.

b. an asteroid.

c. a meteor.

d. a comet.

Standard 5Reactions

Chemical reactions are processes in which atoms are rearranged into different combinations of molecules.

Standard 5Reactions
• Products have different properties from the reactants. (Reactants  Products)
• In chemical reactions, the number of atoms stays the same (Law of Conservation of Mass).
• Chemical reactions are usually exothermic or endothermic.
Standard 5Reactions continued
• Physical processes such as freezing, boiling, and condensation do not involve a chemical change.
• Solutions can be acidic, basic, or neutral.
Question 1

Copper (Cu) reacts with oxygen (O) to form copper oxide (CuO). The properties of CuO are most likely

a. different from copper and oxygen.

b. similar to both copper and oxygen.

c. similar only to copper.

d. similar only to oxygen.

Question 2

The following equations represent chemical reactions.

Which equation shows that the total mass during a chemical reaction stays the same?

a. 1

b. 2

c. 3

d. 4

Question 3

Which of following forms of energy is released or absorbed in most chemical reactions?

a. light energy

b. electrical energy

c. sound energy

d. heat energy

Question 4

As a sample of water turns to ice,

a. new molecules are formed.

b. the mass of the sample is increased.

c. the arrangement of the molecules changes.

d. energy is absorbed by the molecules.

Question 5

The table below shows the pH and reaction to litmus of four body fluids. These data show that gastric juice is

a. very acidic.

b. very basic.

c. positively charged.

d. negatively charged.

Standard 6Chemistry of Living Systems

Principles of chemistry underlie the functioning of biological systems.

Standard 6Chemistry of Living Systems
• Carbon is an important element in living organisms.
• Other important elements are hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
• Living systems are made of polymers such as carbohydrates, fats, proteins, and DNA.
Question 1

Which characteristic most sets carbon apart from other elements?

a. Carbon bonds to many other elements and

to itself in many ways.

b. Carbon is found in living organisms.

c. Carbon is a nonmetal that is solid at 250C.

d. Carbon has more than one electron

available for bonding.

Question 2

Which of the following elements is best able to combine with itself and hydrogen (H) to form large molecules?

a. sodium (Na)

b. lithium (Li)

c. sulfur (S)

d. carbon (C)

Question 3

Which of the following compounds is most likely to be part of living organisms?

a. C6H12O6

b. BF3

c. MoCl2

d. CsI

Question 4

The graph shows the elements found in the human body. Which of these is the missing label?

a. silicon

b. carbon

c. helium

d. water

Standard 7Periodic Table

The organization of the Periodic Table is based on the properties of the elements and reflects the structure of atoms.

Standard 7Periodic Table
• Most elements on the Periodic Table are metals. They are located to the left.
• The zig-zag line is the location of the metalloids.
• To the right are the non-metals.
• Elements are defined by the number of protons or the atomic number.
Standard 7Periodic Table continued
• Isotopes are atoms with different numbers of neutrons.
• Substances are classified by their properties such as melting point, density, hardness, and conductivity.
Question 1

What do the elements sulfur (S), nitrogen (N), phosphorus (P), and bromine (Br) have in common?

a. They are all noble gases.

b. They are nonmetals.

c. They have the same thermal conductivity.

d. They have the same number of protons.

Question 2

A diagram of the periodic table of the elements is shown.

In which region of the table would nonmetals be found?

a. 1

b. 2

c. 3

d. 4

Question 3

The table shows the atomic mass of four stable calcium (Ca) isotopes.

What characteristic is different in each isotope?

a. the position in the periodic table of the elements.

b. the net charge of the nucleus.

c. the mass of the protons in the nucleus.

d. the number of neutrons in the nucleus.

Question 4

Which class of elements best conducts electricity?

a. metals

b. nonmetals

c. semimetals

d. noble gases

Question 5

What is the number of protons in the element radon (Rn)?

a. 18 protons

b. 86 protons

c. 136 protons

d. 222 protons

Question 6

In a comparison of metals to nonmetals, metals tend to have

a. lower melting points and greater conductivity than nonmetals.

b. lower conductivity and lower density than nonmetals.

c. higher density and lower melting points than nonmetals.

d. greater conductivity and higher melting points than nonmetals.

Standard 8Density and Buoyancy

All objects experience a buoyant force when immersed in liquid.

Standard 8Density and Buoyancy
• Density = mass

volume

• The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid it has displaced.
Standard 8Density and Buoyancy
• Know how to measure mass and volume to calculate density.
• An object will float in water if the density is less than 1.0 g/ml.
Question 1

What is the density of a 64 g iron cube that displaces 8 ml of water?

a. 512 g/ml

b. 32 g/ml

c. 8 g/ml

d. 4 g/ml

Question 2

A piece of pine wood floats on the surface of a lake because the water exerts

a. an upward force equal to the weight of the wood.

b. a downward force equal to the weight of the wood.

c. an upward force equal to the weight of the displacement water.

d. a downward force equal to the weight of the displacement water.

Question 3

The following table shows properties of four different sample materials. One of these materials is cork, a type of wood that floats in water.

Given that the density of water is 1 g/ml, which of the samples is most likely cork?

a. 1

b. 2

c. 3

d. 4

Question 4

The densities of four different woods are shown.

Which wood will sink when placed in a fluid with a density of 1.14 g/cm3

a. African teakwood

b. balsa

c. cedar

d. ironwood

Standard 9Investigation and Experimentation

Scientific progress is made by asking meaningful questions and conducting careful investigations.

Standard 9Investigation and Experimentation

Step of the Scientific Method

• Step 1 – State the problem
• Step 2 – Gather Information
• Step 3 – Form a hypothesis
• Step 4 – Conduct an experiment
• Step 5 – Form a conclusion
• Step 6 – Share results
Question 1

The graph below shows the movement of an object at several points in time.

What is the average speed of the object?

a. 0.5 meters/minute

b. 2 meters/minute

c. 25 meters/minute

d. 50 meters/minute

Question 2

Data from an experiment are presented.

The slope of the graph represents what characteristic of an object?

a. displacement

b. force

c. speed

d. inertia

Question 3

A spring scale is pulled downward and readings are recorded.

If the spring scale is pulled 3.5 cm, the spring scale should read

a. 12 N.

b. 13 N.

c. 14 N.

d. 15 N.

Question 4

A student records the mass and volume of a lump of clay, x. Next, a second lumps of clay, y, is added to lump x, and the combined (x + y) mass and volume are recorded. Finally, a third lump of clay, z, is added to the combined (x + y) mixture and the final (x + y + z) mass and volume are recorded, as shown.

What is the most logical conclusion about the clay used in this investigation?

a. Lump z has the greatest mass.

b. Lump z has the lowest density.

c. Lump y has the lowest density.

d. Lump y has the greatest mass.

Question 5

Red-clay bricks have a density of approximately 200 kg/m3. Air has a density of 1 kg/m3. Which of the following has the lowest mass?

a. 2 m3 of bricks

b. 4 m3 of bricks

c. 6000 m3 of air

d. 10,000 m3 of air