8 th Grade Comprehensive Science

1. 8th Grade Comprehensive Science Mid-Term Exam Review 2015

2. What we learned.. • Big Idea 1: The Practice of Science • Big Idea 2: The Characteristics of Scientific Knowledge • Big Idea 3: The Role of Theories, Laws, Hypotheses, and Models • Big Idea 4: Science and Society • Big Idea 5: Earth in Space and Time

3. The Practice of Science • Scientific Inquiry is an activity requiring many steps. • Formulating an investigable question • Planning an investigation to answer the question • The collection of appropriate data • Drawing a conclusion based on the data • Communicating the results of the investigation

4. The scientific process does not always follow the scientific method • Other types of investigations include observational studies • Scientists must remain creative, not only in their methods and processes, but also in their questions and explanations • Scientists may use a variety of models such as physical or computer to simulate things that are too dangerous, expensive, big or small.

5. Scientific Argumentation • Scientists must be prepared to debate or validate the results of their scientific inquiry. • This is an important part of generating new ideas and communicating results.

6. Observation Noting a fact or occurrence Using one’s senses to perceive something without any assumptions. Ex: The boy is running at 5 pm. Inference Arriving at a conclusion based on an observation An assumption based on probability. Ex: The boy is running home for dinner Observation vs. Inference

7. A Science Experiment: • A student asks the question: What fertilizer will make my plant grow taller in one month. • The student designs an experiment: 4 identical plants, in the same soil, in the same size container, receiving the same amount of light. • 3 brands of fertilizer, brand a, brand b, brand c. • The student has seen several commercials for brand b, does some research on all the brands.

8. An experiment continued • Based on the research, the student states a hypothesis: “Brand B will make the plant grow taller in one month than the other brands.” • The student carries out the experiment: • Measures and records the starting height of each plant. • Gives each plant the same amount of soil, water and sunlight keeping as many variables constant as possible

9. An Experiment continued: • The student puts equal amounts of each fertilizer on different plants. One plant gets no fertilizer. This is the control. (the independent variable is not applied-used for comparison) • The type of plant, the kind and amount of soil, the container, the amount of water, fertilizer, and sunlight are all constants. (the factors that must stay the same) • The fertilizer brands are the independent variable. (The factor being tested)

10. An Experiment continued • The student gives each plant equal amounts of water and measures each plant carefully every three days for a month. The amount of growth is the Dependent Variable (What is being measured) • The student takes organized notes and details the growth of each plant on a table. • At the end of 30 days, the student is ready to analyze and interpret the data.

11. Drawing a conclusion • The student finds the plant that received fertilizer A grew taller than the other plants in 30 days. • Has the student finished the project? What must every experiment be in order to be considered valid?

12. Repeatable! • In order to be a valid experiment, a scientists must conduct multiple trials. • Other scientists must be able to perform the same experiment. • If after several trials, Fertilizer A continues to produce the most growth, the scientist states that the hypothesis was NOT supported. (A hypothesis is never right or wrong, it is either supported or not supported by the evidence/data of the experiment!)

13. Does this mean the experiment was a failure? • No! The student has acquired valuable information. • The student can now modify (change) the hypothesis to reflect their new knowledge. • Based on this new information, the scientist can perform further studies possibly using a different type of plant or changing another variable. • A negative result can lead to further investigation!

14. Empirical Data Obtained through experimentation Provable through experimentation Pseudoscience A theory or claim having no scientific basis “pseudo” is Latin for false Empirical Data vs. Pseudoscience Empirical data or pseudoscience?: You see a commercial that says you will look younger if you use their skin cream.

15. Science is knowledge of the physical or material world gained through observation and experimentation • Science can not explain or answer every question about the supernatural, art, philosophy, religion, ethics, or politics. • Science can supply information to help people make decisions. Ex: Cloning • Political, social and economical concerns can also effect science. Ex: ending the space program in Florida

16. The Roll of Theories, Laws, Hypotheses and Models • Theories are well tested scientific beliefs. They are believed to be true but could change or modify if new information were to be obtained. • For example: For many years, people believed the Earth was the center of the solar system ( Geocentric model). This theory changed when the telescope was invented. (Heliocentric model)

17. Theories in science Have: • Multiple lines of evidence • Have been tested over time • Are generally accepted as “true” by scientists in that field • Are predictive (can be applied to future events)

18. Scientific Law • Scientific laws are based on things that do not change. They do not have to be explained. • Examples: the law of gravity, the law of conservation of matter, the law of conservation of energy, Newton’s laws, etc.

19. Space! • Our Solar System: • There have been two models of the solar system, heliocentric and geocentric. • Our Sun is just one of the billions of stars in the Milky Way galaxy. • The distance between planets is very small when compared to the distance between stars. • Nothing in our solar system is a light year away.

20. Distance in Space • Within our solar system we measure distance in AU’s, or Astronomical Units. • One AU is equal to the average distance between the Earth and the Sun or 150,000,000 km. • The inner planets are fairly close together whereas the outer planets are very far apart. • The inner planets are all small and rocky. • The outer planets are large and gaseous.

21. Objects in our Solar System • In addition to the Sun and planets, our Solar System contains: • Moons- they stay in orbit around individual planets. • Asteroids- they are found in the asteroid belt between Mars and Jupiter. They orbit the Sun, not planets • Comets- originate in the Kuiper Belt, travel from the edge of the solar system, around the sun, and back to the edge again. • Meteors, Meteorites, Meteoroids

22. Gravity’s Impact in Space • Gravity is responsible for the formation of Stars and Planets • Gravity keeps planets in orbit around the Sun • Gravity keeps moons in orbit around planets • Gravity keeps stars in orbit around the center or galaxies

23. Earth Orbits the Sun, the Moon Orbits the Earth • How does this affect us? • As the Earth orbits the Sun, sometimes it is closer to the Sun (January), sometimes further away (July). This does NOT cause us to have seasons. • We experience season’s on Earth because the Earth is slightly tilted on it’s axis. • The hemisphere tilted toward the Sun experiences summer, the hemisphere tilted away experiences winter.

24. The Moon Orbits Earth • As the moon moves around Earth, varying amount of it’s surface shows. • This is because the moon does not produce it’s own light. It only reflects the light from the Sun. • We call these varying amounts of light phases. New moon, waxing crescent, 1st quarter, waxing gibbous, Full moon, waning gibbous, 3rd quarter, waning crescent. • The moon’s gravity causes tides on Earth

25. Eclipses • Sometimes the Moon moves into the Earth’s shadow. This is called a Lunar Eclipse. Earth’s shadow moves over the moon. • Rarely, the moon casts a shadow on Earth. This shadow is called the Umbra. When this happens, the Sun is momentarily blocked from view from Earth. • The penumbra is the shadow around the umbra. People in this area see a partial eclipse. • Solar eclipses are rare because the moons shadow is very small.

26. Outside of our Solar System • The distance to everything outside of our solar system is measured in Light Years. • One light year is the distance light will travel in one year. 186,000 miles per second or 300,000 km per second • The closest star to our solar system is over 4 light years away. • That means that when we look at that star, we are seeing it how it appeared 4 years ago. • Some of the stars we see in the night sky are millions of light years away!

27. The magnitude of Stars • Some stars in the sky appear to be brighter than others. Sometimes they only appear brighter because they are closer. • How bright a star really is, is it’s Absolute Magnitude or Absolute Brightness • How bright a star appears from Earth is it’s Apparent Magnitude.

28. The Sun and other Stars • Stars produce light and heat through Nuclear Fusion. • Our Sun has many layers. Since the layers are not solid, they rotate at different rates. • Convection occurs at one layer which is the rising and falling of gas. • On another layer sunspots, prominences, and solar flares occur. • The color of a star indicates how hot the star is. • Blue stars are the hottest • Red stars are the coolest

29. How stars are classified • Stars can be classified on the HR diagram according to their magnitude and temperature. • The stars the fall across the center of the diagram are called “main sequence” stars. • Our sun is a very average main sequence star.

30. Electromagnetic Spectrum • The electromagnetic spectrum makes up the radiation that is sent to Earth from the Sun.

31. Electromagnetic Spectrum Continued.. • Although we can not see them all, these waves are all around us: • Radio waves carry communication and television signals • Microwaves also are used for communication • Infrared waves are used by remote controls • Ultraviolet waves cause sunburn and can cause skin cancer • X rays are used for medical purposes • Gamma rays are used to kill cells

32. Electromagnetic Spectrum Continued.. • Notice that radio waves have the largest wavelength and that gamma rays have the smallest. • Waves with smaller wavelengths are more dangerous to humans. • Many of the dangerous waves from the Sun are blocked by the ozone layer in Earth’s atmosphere.

33. The Universe • The Universe is made up of clusters of billions of galaxies. • Our Sun is in the Milky Way Galaxy • Each Galaxy is made up of clusters of billions of stars. • Not all galaxies are the same shape, but they all rotate around their centers.