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 Instructional Focus DocumentIPC Chemistry First
 TITLE : Unit 07: Forces and Momentum SUGGESTED DURATION : 11 days

#### Unit Overview

Introduction

This unit focuses on the effects of force and momentum on motion as well as two of the fundamental forces of nature (electrical and gravity).

Prior to this Unit

• 6.8B –Identify and describe the changes in position, direction, and speed of an object when acted upon by unbalanced forces.
• 6.8D – Measure and graph changes in motion.
• 6.8E – Investigate how inclined planes can be used to change the amount of force to move an object.
• 6.11B – Understand that gravity is the force that governs the motion of our solar system.
• 8.6A – Demonstrate and calculate how unbalanced forces change the speed or direction of an object's motion.
• 8.6C – Investigate and describe applications of Newton's three laws of motion such as in vehicle restraints, sports activities, amusement park rides, Earth's tectonic activities, and rocket launches.
• 8.7C – Relate the positions of the Moon and Sun to their effect on ocean tides.

During this Unit

Students will investigate how an object’s motion changes due to force. Students describe the relationship between force, mass, and acceleration and use the formula F=ma to calculate each value given different scenarios. Students only explore momentum in terms of how action and reaction forces conserve momentum. Students explore gravity and electrical forces independently of each other as naturally occurring forces that depend on the properties of the objects influenced by the forces.

Streamlining Note

Students no long are expected to compare the relative strength of electrical and gravitational force as part of TEKS I.4G.

After this Unit

Students will recognize systems involving force and momentum in their everyday lives. Students that enroll in High School Physics will continue to analyze how motion is affected by force and momentum.

Research

“By the end of the 12th grade, students should know that:

• The change in motion (direction or speed) of an object is proportional to the applied force and inversely proportional to the mass.
• Whenever one thing exerts a force on another, an equal amount of force is exerted back on it.
• Any object maintains a constant speed and direction of motion unless an unbalanced outside force acts on it.
• Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them.
• Electric forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms. At larger scales, gravitational forces accumulate to produce a large and noticeable effect, whereas electric forces tend to cancel each other out.”

 Scientists investigate natural phenomena in order to understand and explain each phenomenon in terms of systems. How are the properties of systems and their components related to their classification? How are the components, processes, and / or patterns of systems interrelated?   Scientific investigation is an orderly process to ensure that scientific claims are credible. How is scientific knowledge generated and validated?   Data is systematically collected, organized, and analyzed in terms of patterns and relationships to develop reasonable explanations and make predictions. What gives meaning to data?  What is the value of observing patterns and relationships in data?   Scientists analyze, evaluate, and critique each other’s work using principles of scientific investigations in order to build on one another’s ideas through new investigations. How can we know what to believe about a scientific claim? In what ways have scientific explanations impacted scientific thought and society over time? What is the value of scientific literacy?
Unit Understandings
and Questions
Overarching Concepts
and Unit Concepts
Performance Assessment(s)

Unbalanced forces cause changes in motion.

• What can be true about an object’s motion while unbalanced forces are acting on it?

When two objects collide, the sum of their momentum will not change because the action and reaction forces are equal.

• How is momentum conserved between two objects in a collision when many of the other characteristics of the objects’ motions changes?

Systems

• Motion

Properties

• Force
• Momentum
• Mass
• Acceleration

Patterns

• Inverse relationships
• Direct relationships

Constancy

• Force formula
• Momentum formula
 Assessment information provided within the TEKS Resource System are examples that may, or may not, be used by your child’s teacher. In accordance with section 26.006 (2) of the Texas Education Code, "A parent is entitled to review each test administered to the parent’s child after the test is administered." For more information regarding assessments administered to your child, please visit with your child’s teacher.

Objects have a natural force of attraction or repulsion with each other based on their properties.

• In what ways can gravitational attraction change between two objects?
• What are the distinguishing characteristics of electrical forces?

Systems

• Motion

Classifications

• Electrical force
• Gravitational force

Properties

• Mass
• Charge
• Distance between objects

Patterns

• Inverse relationships
• Direct relationships

Constancy

• Universal gravitation

Change

• Strength of force
 Assessment information provided within the TEKS Resource System are examples that may, or may not, be used by your child’s teacher. In accordance with section 26.006 (2) of the Texas Education Code, "A parent is entitled to review each test administered to the parent’s child after the test is administered." For more information regarding assessments administered to your child, please visit with your child’s teacher.

#### MISCONCEPTIONS / UNDERDEVELOPED CONCEPTS

Misconceptions:

• Students may think an object a person is sitting or standing on does not push back with equal force, rather than all actions having equal and opposite reactions that act in force pairs.
• Students may think friction is not a force, rather than friction being the force that brings most objects to a stop.
• Students may think that unbalanced forces can only change an objects speed, rather than understanding that forces can change an objects direction without affecting speed.

#### Unit Vocabulary

Key Content Vocabulary:

• Electrical force – a universal force between any two charged objects
• Gravitational force – the force of attraction between all masses in the Universe
• Law of conservation of momentum – for a collision occurring between two objects in a closed system, the total momentum of the two objects prior to the collision is equal to the total momentum of the two objects after the collision; momentum lost by first object is gained by second object
• Law of universal gravitation – any two bodies in the Universe attract one another with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
• Momentum – the quantity of motion of a moving object; expressed as the product of mass times velocity
• Unbalanced forces – forces acting on the object that are not equal in opposite directions, resulting in a change in motion

Related Vocabulary:

 Action force Attract Balanced forces Force Friction Gravity Negative charge Net force Positive charge Reaction force Repel Weight
Unit Assessment Items System Resources Other Resources

Show this message:

Unit Assessment Items that have been published by your district may be accessed through Search All Components in the District Resources tab. Assessment items may also be found using the Assessment Center if your district has granted access to that tool.

System Resources may be accessed through Search All Components in the District Resources Tab.

State:

Texas Education Agency – Texas Safety Standards

http://www.tea.state.tx.us/index2.aspx?id=5483 (look under Documents)

Texas Gateway for Online Resources by TEA – Conservation of Momentum

https://www.texasgateway.org/resource/conservation-momentum

Texas Gateway for Online Resources by TEA – Gravitational Force

https://www.texasgateway.org/resource/gravitational-force

Texas Gateway for Online Resources by TEA – OnTRACK Scientific Process Skills

https://www.texasgateway.org/binder/ontrack-scientific-process-skills

TAUGHT DIRECTLY TEKS

TEKS intended to be explicitly taught in this unit.

TEKS/SE Legend:

• Knowledge and Skills Statements (TEKS) identified by TEA are in italicized, bolded, black text.
• Student Expectations (TEKS) identified by TEA are in bolded, black text.
• Portions of the Student Expectations (TEKS) that are not included in this unit but are taught in previous or future units are indicated by a strike-through.

Specificity Legend:

• Supporting information / clarifications (specificity) written by TEKS Resource System are in blue text.
• Unit-specific clarifications are in italicized, blue text.
• Information from Texas Education Agency (TEA), Texas College and Career Readiness Standards (TxCCRS), and American Association for the Advancement of Science (AAAS) Project 2061 is labeled.
• A Partial Specificity label indicates that a portion of the specificity not aligned to this unit has been removed.
TEKS# SE# TEKS SPECIFICITY
I.1 Scientific processes. The student, for at least 40% of instructional time, conducts laboratory and field investigations using safe, environmentally appropriate, and ethical practices. The student is expected to:
I.1A

Demonstrate safe practices during laboratory and field investigations, including the appropriate use of safety showers, eyewash fountains, safety goggles or chemical splash goggles, as appropriate, and fire extinguishers.

Demonstrate

SAFE PRACTICES DURING FIELD AND LABORATORY INVESTIGATIONS

Including, but not limited to:

• Wear appropriate safety equipment, such as goggles, aprons, and gloves
• Know location of safety equipment, such as fire extinguisher, safety shower, and eye wash
• Follow classroom guidelines, as outlined in the Texas Education Agency Texas Safety Standards
• Possible examples may include:
• Read or study the science activity or laboratory investigation prior to conducting the investigation
• Know and follow all safety rules prior to and during the investigation
• Be alert during the laboratory time
• Do not attempt unauthorized activities
• Do not enter preparatory or equipment storage rooms or chemical storerooms
• Always wash your hands for at least 20 seconds with soap and warm water before leaving the laboratory
I.2 Scientific processes. The student uses scientific practices during laboratory and field investigations. The student is expected to:
I.2B Plan and implement investigative procedures, including asking questions, formulating testable hypotheses, and selecting equipment and technology.

Plan, Implement

INVESTIGATIVE PROCEDURES

Including, but not limited to:

• Observe natural phenomena
• Formulate testable hypotheses
• Plan and implement investigations
• Select appropriate equipment and technology
I.2C Collect data and make measurements with accuracy and precision.

Collect

DATA

Including, but not limited to:

• Observations
• Measurements
• Demonstrate use of appropriate equipment to collect data
• Possible equipment for use in data collection may include:
• Calculator
• Spring scale
• Triple beam balance
• Electronic balance
• Meter stick
• Metric ruler

Make

MEASUREMENTS WITH PRECISION

Including, but not limited to:

• Accuracy
• Precision

Note(s):

• TxCCRS:
• I. Nature of Science – A4 – Rely on reproducible observations of empirical evidence when constructing, analyzing, and evaluating explanations of natural events and processes.
I.2D Organize, analyze, evaluate, make inferences, and predict trends from data.

Organize, Analyze, Evaluate, Make inferences, Predict

TRENDS FROM DATA

Including, but not limited to:

• Use appropriate standard international (SI) units
• Use appropriate mathematical calculations
• Possible examples may include:
• Averaging
• Percent change
• Probabilities and ratios
• Rate of change
• Analyze data using different modes of expression (narrative, numerical, graphical)
• Accurately predict trends from data

Note(s):

• TxCCRS:
• I. Nature of Science – A4 – Rely on reproducible observations of empirical evidence when constructing, analyzing, and evaluating explanations of natural events and processes.
I.2E Communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphs, journals, summaries, oral reports, and technology-based reports.

Communicate

VALID CONCLUSIONS SUPPORTED BY DATA

Including, but not limited to:

• Communicate conclusions in oral, written, and graphic forms
• Use essential vocabulary of the discipline to communicate conclusions
• Use appropriate writing practices consistent with scientific writing
• Present scientific information in appropriate formats for various audiences
• Various methods for communicating conclusions may include:
• Lab reports
• Labeled drawings
• Diagrams
• Graphic organizers (including charts and tables)
• Graphs
• Journals (science notebooks)
• Summaries
• Oral reports
• Technology-based reports

Note(s):

• TxCCRS:
• IV. Nature of Science: Scientific Ways of Learning and Thinking – E1 – Use several modes of expression to describe or characterize natural patterns and phenomena. These modes of expression include narrative, numerical, graphical, pictorial, symbolic, and kinesthetic.
I.3 Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions. The student is expected to:
I.3A Analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, so as to encourage critical thinking by the student.

Analyze, Evaluate, Critique

SCIENTIFIC EXPLANATIONS, SO AS TO ENCOURAGE CRITICAL THINKING BY THE STUDENT

Including, but not limited to:

• Use
• Empirical evidence
• Logical reasoning
• Experimental and observational testing
• Examine
• All sides of scientific evidence of those explanations

Note(s):

• Project 2061: By the end of the 8th grade, students should know that:
• Scientific knowledge is subject to modification as new information challenges prevailing theories and as a new theory leads to looking at old observations in a new way. 1A/M2
• Some scientific knowledge is very old and yet is still applicable today. 1A/M3
• Scientific investigations usually involve the collection of relevant data, the use of logical reasoning, and the application of imagination in devising hypotheses and explanations to make sense of the collected data. 1B/M1b*
• If more than one variable changes at the same time in an experiment, the outcome of the experiment may not be clearly attributable to any one variable. It may not always be possible to prevent outside variables from influencing an investigation (or even to identify all of the variables). 1B/M2ab
• TxCCRS:
• I. Nature of Science – A1 – Utilize skepticism, logic, and professional ethics in science.
• I. Nature of Science – A4 – Rely on reproducible observations of empirical evidence when constructing, analyzing, and evaluating explanations.
I.3B Communicate and apply scientific information extracted from various sources such as current events, published journal articles, and marketing materials.

Communicate, Apply

SCIENTIFIC INFORMATION

Including, but not limited to:

• Review scientific information from a variety of sources
• Summarize and communicate scientific information from a variety of sources
• Evaluate the quality and accuracy of information from research sources
• Current events
• News reports
• Published journal articles
• Marketing materials
• Possible additional sources may include:
• Books
• Interviews, conference papers
• Science notebooks
• Search engines, databases, and other media or online tools
I.3C Draw inferences based on data related to promotional materials for products and services.

Draw

INFERENCES

Including, but not limited to:

• Examine data from promotional materials for products and services described in print, on television, and on the Internet
• Evaluate data for quality and accuracy
• Evaluate completeness and reliability of information from sources
I.3E

Describe connections between physics and chemistry and future careers.

Describe

CONNECTIONS BETWEEN PHYSICS AND FUTURE CAREERS

Including, but not limited to:

• How physics is used in various careers
• Physics
• Possible examples may include:
• Astronomer
• Teacher
• Geophysicist
• Equipment designer
• Materials designer
• Engineer
I.3F

Research and describe the history of physics and chemistry and contributions of scientists.

Research, Describe

HISTORY OF PHYSICS AND CONTRIBUTIONS OF SCIENTISTS

Including, but not limited to:

• Conduct research on significant events in the history of physics
• Conduct research on contributions of various physicists
• Possible examples may include:
• Newton (developed theories of gravitation and mechanics; invented differential calculus)
I.4 Science concepts. The student knows concepts of force and motion evident in everyday life. The student is expected to:
I.4C Investigate how an object's motion changes only when a net force is applied, including activities and equipment such as toy cars, vehicle restraints, sports activities, and classroom objects.

Investigate

HOW AN OBJECT’S MOTION CHANGES ONLY WHEN A NET FORCE IS APPLIED

Including, but not limited to:

• The effects of balanced and unbalanced forces on objects
• Forces
• Gravity
• g = 9.8 m / s2
• g = acceleration due to gravity
• Friction
• Magnetism
• Newton’s laws of motion
• Inertia
• Mass
• Net force
• Fnet = ma
• Net force = (mass)(acceleration)
• Activities and equipment such as
• Toy cars
• Vehicle restraints
• Sports activities
• Classroom objects

Note(s):

• The STAAR Physics Reference Materials include the formula for Net force and the constant for gravity as listed above.
• Students are introduced to the concepts of force in Grades 6 and 8 by observing change in the motion of an object that is acted upon by an unbalanced force (6.8B, 8.6A).
• Students in Grade 6 investigate how inclined planes can be used to change the force applied to an object (6.8E).
• Students in Grade 7 consider how forces affect motion in organisms (7.7B).
• Students in Grade 8 are introduced to Newton’s Laws of Motion (8.6C).
• TxCCRS:
• VIII. Physics – A3 – Understand the concepts of mass and inertia.
• VIII. Physics – C1 – Understand the fundamental concepts of kinematics.
• VIII. Physics – C2 – Understand forces and Newton’s Laws.
I.4D Describe and calculate the relationship between force, mass, and acceleration using equipment such as dynamic carts, moving toys, vehicles, and falling objects.

Describe, Calculate

RELATIONSHIP BETWEEN FORCE, MASS, AND ACCELERATION

Including, but not limited to:

• Relationship is independent of the nature of the force
• The greater the force acting on an object, the greater the acceleration or change in motion of that object (constant mass)
• The greater the mass of an object, the less the acceleration or change in motion of that object (constant force)
• The greater the mass of an object, the greater the force needed to accelerate it to a given acceleration
• Newton’s second law of motion
• Force = mass x acceleration
• F = ma
• Newton (N) = kg • m / s
• Gravity
• g = 9.8 m / s2
• g = acceleration due to gravity
• Friction
• Equipment such as
• Dynamic carts
• Moving toys
• Vehicles
• Falling objects

Note(s):

• The STAAR Grade 8 Science Reference Materials include the formula for Net force as listed above.
• The STAAR Physics Reference Materials include the constants for gravity and newton as listed above.
• Students in Grade 8 are introduced to Newton’s laws of motion (8.6C).
• TxCCRS:
• VIII. Physics – A3 – Understand the concepts of mass and inertia.
• VIII. Physics – C1 – Understand the fundamental concepts of kinematics.
• VIII. Physics – C2 – Understand forces and Newton’s Laws.
I.4E Explain the concept of conservation of momentum using action and reaction forces.

Explain

CONCEPT OF CONSERVATION OF MOMENTUM

Including, but not limited to:

• p = mv
• Momentum = (mass)(velocity)
• Law of conservation of momentum
• The sum of the momentum of two colliding objects will be the same before and after the collision because the action and reaction forces are equal.
• Initial Momentum of Object 1 + Initial Momentum of Object 2 = Final Momentum of Object 1 + Final Momentum of Object 2
• m1v1i + m2v2i = m1v1f + m2v2f
• Action and reaction forces
• Newton’s third law

Note(s):

• The STAAR Physics Reference Materials include the formula for momentum as listed above.
• Students in Grade 8 are introduced to Newton’s Laws of Motion (8.6C).
• TxCCRS:
• VIII. Physics – C1 – Understand the fundamental concepts of kinematics.
• VIII. Physics – C3 – Understand the concept of momentum.
I.4F Describe the gravitational attraction between objects of different masses at different distances.

Describe

THE GRAVITATIONAL ATTRACTION BETWEEN OBJECTS

Including, but not limited to:

• Relationship between mass and the force of gravity
• Planets or moons
• Relationship between distance and the force of gravity
• Inverse squared relationship between distance and the force of gravity
• Newton’s law of universal gravitation

Note(s):

• Students may use the equation for gravitational attraction in order to understand the relationship between mass / distance and gravitational attraction, but are not required to calculate gravitational attraction using the equation. The STAAR Physics Reference Materials include the formula for gravitational attraction.
• Students in Grade 6 study gravity as the force that controls the motion of the components of our solar system (6.11B).
• TxCCRS:
• VIII. Physics – A5 – Understand the concepts of gravitational force and weight.
I.4G Examine electrical force as a universal force between any two charged objects.

Examine

ELECTRICAL FORCE

Including, but not limited to:

• A universal force between any two charged objects
• Factors affecting electrical force
• Charge
• Distance

Note(s):

• This is the first time students have been directly introduced to the concept of universal force.
• TxCCRS:
• VIII. Physics – I1 – Discuss electric charge and electric force.
DEVELOPING TEKS

TEKS that need continued practice, improvement, and refinement, but do not necessarily need to be explicitly taught in this unit.

TEKS/SE Legend:

• Knowledge and Skills Statements (TEKS) identified by TEA are in italicized, bolded, black text.
• Student Expectations (TEKS) identified by TEA are in bolded, black text.
• Portions of the Student Expectations (TEKS) that are not included in this unit but are taught in previous or future units are indicated by a strike-through.

Specificity Legend:

• Supporting information / clarifications (specificity) written by TEKS Resource System are in blue text.
• Unit-specific clarifications are in italicized, blue text.
• Information from Texas Education Agency (TEA), Texas College and Career Readiness Standards (TxCCRS), and American Association for the Advancement of Science (AAAS) Project 2061 is labeled.
TEKS# SE# TEKS SPECIFICITY
I.1 Scientific processes. The student, for at least 40% of instructional time, conducts laboratory and field investigations using safe, environmentally appropriate, and ethical practices. The student is expected to:
I.1B Know specific hazards of chemical substances such as flammability, corrosiveness, and radioactivity as summarized on the Safety Data Sheets (SDS).

Know

SPECIFIC HAZARDS OF CHEMICAL SUBSTANCES SUMMARIZED ON THE SDS

Including but not limited to:

• Hazard information
• Hazard pictograms
• Signal words
• Hazard statements
• Precautionary statements
• First aid measures
• Fire – fighting measures
• Accidental release measures
• Handling and storage
• Exposure controls / personal protection
• PPE pictograms
• Stability and reactivity
• Toxicological information
• Ecological information
• Disposal considerations
I.1C Demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials.

Demonstrate

AN UNDERSTANDING OF THE USE AND CONSERVATION OF RESOURCES AND THE PROPER DISPOSAL OR RECYCLING OF MATERIALS

Including, but not limited to:

• Use and conservation of resources
• Reducing pollution
• Being a wise consumer
• Awareness of reliance on fossil fuels
• Preserving habitats
• Proper disposal or recycling of materials
I.2 Scientific processes. The student uses scientific practices during laboratory and field investigations. The student is expected to:
I.2A Know the definition of science and understand that it has limitations, as specified in subsection (b)(2) of this section.

Know

THE DEFINITION OF SCIENCE

Including, but not limited to:

• Science, as defined by the National Academy of Sciences, is the "use of evidence to construct testable explanations and predictions of natural phenomena, as well as the knowledge generated through this process."

Understand

SCIENCE HAS LIMITATIONS

Including, but not limited to:

• “...some questions are outside the realm of science because they deal with phenomena that are not scientifically testable.”
• Scientific inquiry may be limited by current technology
I.3 Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions. The student is expected to:
I.3D Evaluate the impact of research on scientific thought, society, and the environment.

Evaluate

IMPACT OF RESEARCH

Including, but not limited to:

• Read scientific articles to gain understanding of the impact of research
• Evaluate the impact of research on society, everyday life, and the environment
• Recognize how scientific discoveries are connected to technological innovations
• Understand how scientific research and technology have an impact on ethical and legal practices
• Understand how commonly held ethical beliefs impact scientific research
• Understand how scientific discoveries have impacted / changed commonly held beliefs

Note(s):

• TxCCRS:
• I. Nature of Science – A4 – Rely on reproducible observations of empirical evidence when constructing, analyzing, and evaluating explanations of natural events and processes.
I.4 Science concepts. The student knows concepts of force and motion evident in everyday life. The student is expected to:
I.4A Describe and calculate an object's motion in terms of position, displacement, speed, and acceleration.

Describe, Calculate

OBJECT’S MOTION

Including, but not limited to:

• Position
• Displacement
• Differentiate between displacement and distance
• Displacement = change in position = final position – initial position
• d = ∆x = x– xi
• Speed
• Average speed = total distance / total time
• s = d / t
• Speed = distance traveled / time
• Acceleration
• Acceleration = final velocity – initial velocity / change in time
• a = vf – vi / ∆t
• Acceleration = (final velocity)2 – (initial velocity)2 / 2(displacement)
• a = vf2 – vi2 / 2∆d
• Velocity
• Velocity = distance / time
• v = d / t
• Instantaneous speed

Note(s):

• The STAAR Grade 8 Science Reference Materials include the formula for average speed as listed above.
• The STAAR Physics Reference Materials include the formulas for acceleration and displacement as listed above.
• Students in Grade 6 calculate average speed using distance and time measurements, measure and graph changes in motion, and investigate how inclined planes can be used to change the amount of force to move an object (6.8C, 6.8D, 6.8E).
• Students in Grade 8 differentiate between speed, velocity, and acceleration (8.6B).
• TxCCRS:
• VIII. Physics – C1 – Understand the fundamental concepts of kinematics.
I.4B Measure and graph distance and speed as a function of time.

Measure, Graph

DISTANCE AND SPEED AS A FUNCTION OF TIME

Including, but not limited to:

• Interpretation and construction of graphs that relate to change in motion
• Distance vs. time and velocity vs. time graphs
• Slope
• Negative and positive acceleration
• Direction of motion (toward or away from a reference point)
• Apply distance vs. time and velocity vs. time graphs to scenarios

Note(s):

• Students in Grade 6 measure and graph changes in motion, in terms of distance over time and velocity over time (6.8C, 6.8D).