Physical Science
Imagine you are at a birthday party. A birthday cake with candles is put on a table in the middle of a room. The room is very large. You are standing at the end of the room, 10 meters away from the cake. You can see the candles. How far did the light from the candles traveled in order for you to see the flames, and why do you think that?
A) The light stays on the candle flames.
B) The light travels a few centimeters from the candle flames.
C) The light travels about 1 meter.
D) The light travels about halfway to where you are standing.
E) The light travels all the way to where you are standing.
The best response is E) The light travels all the way to where you are standing. The light from the candles will travel away from its source (the flame) to you as long as it is unobstructed by an object or material. Since you can see the candlelight, it has traveled outward from its source—the candle flame—through the room and to your eyes. For you to see the flame, the light emitted from the flame must reach your eye. The eyes are the object, or matter, that the light comes in contact with. Even though it may appear that in a lit room that there is only light around the candle, since that is what you can detect with their senses, light is radiating outward in all directions beyond the visible part of the flame, including the space between the light source and the eye of the observer
Six friends were talking about the function of the digestive system. This is what they said:
Mina:“I think the main function is to release energy from food.”
Manny:“I think the main function is to help us breathe.”
Sasha:“I think the main function is to break food down into molecules that can be absorbed by cells.”
Harriet:“I think the main function is to break food down in the stomach into small pieces of food that can be used by the body.”
Todd:“I think the main function is to carry bits of food and nutrients to all the different parts of our body.”
Curtis:“I think the main function is to store food so that we can get energy when we need it."
Who do you agree with? Why?
The best answer is Sasha’s: “I think the main function is to break food down into molecules that can be absorbed by cells.” There is no single purpose of the digestive system; rather, it has two major purposes: (1) to break down food and (2) to prepare nutrients for absorption by cells. The digestive system carries out six basic functions: taking food in (ingestion), secretion, movement of food and wastes, break-down of food, absorption from gastrointestinal tract to cells, and removal of wastes.
Five friends noticed they could see better at night when there was a full Moon. They wondered where the moonlight came from. This is what they said:
Curtis:“The Moon reflects the light from the Earth.”
Chet:“The light from the Sun bounces off the Moon.”
Clarence: “The Moon gets its light from distant stars.”
Fallon:“The Moon absorbs light from the Sun during the day.”
Deirdre:“There is light inside of the Moon that makes it shine.”
The best answer is Chet’s: “The light from the Sun bounces off the Moon.” In other words, the Moon reflects sunlight. Even though you do not see the Sun in the evening, it does shine on the surface of the Moon. The light from the Sun reflects off the Moon and travels to Earth. Therefore, during a full Moon, the moonlight that helps us see better during the evening after the Sun has set it actually sunlight that is bouncing off the Moon, striking the Earth, reflecting off objects, and entering our eyes, which allows us to see things at night. When there is no full Moon, there is less light reaching and reflecting off the Earth; therefore, we see better when there is a full Moon. In contrast, stars emit their own light. They are sources of light rather than objects that reflect light.
Imagine you are sitting at a table with a red apple in front of you. Your friend closes the door and turns off all the lights. It is totally dark in the room. There are no windows in the room or cracks around the door. No light can enter the room. What answer best describes how you would see the apple in the dark, and why?
A) You will not see the red apple, regardless of how long you are in the room.
B) You will see the red apple after your eyes have had time to adjust to the darkness.
C) You will see the apple after your eyes have had time to adjust to the darkness, but you will not see the red color.
D) You will see only the shadow of the apple after your eyes have had time to adjust to the darkness.
E) You will see only a faint outline of the apple after your eyes have had time to adjust to the darkness.
The best response is A) You will not see the red apple, regardless of how long you are in the room.
In order to see an object, light must be emitted from or reflected off an object so that it reaches the eye. The path of light is from the object to the eye. It is impossible to see an object in the absence of light (total darkness). Emitted or reflected light must enter the eye in order to see an object!
Sam brought home a tiny puppy. Her puppy grew. Four weeks later, her puppy had grown to twice its original size. Which answer below best explains why Sam’s puppy got bigger and why?
A) The number of cells in the puppy’s body increased.
B) The puppy’s body absorbed the food it ate.
C) The puppy’s body cells grew larger as it got older.
D) Parts of the puppy’s body stretched out more.
The best response is A: The number of cells in the puppy’s body increased. Body cell reproduction involves producing new cells for growth of tissues as well as repair and replacement of old cells. Growth is the term for the overall increase in an organism’s size. It is a complex process, but to describe it in simple terms, growth primarily involves cell enlargement as new molecules are added to the cell’s mass and subsequent cell division. Food and nutrients taken in by the puppy are broken down at a molecular level, transformed within cells, and become the building blocks for new living material, including new cells produced through cell division.
People have been fascinated by lunar (Moon) eclipses for ages. For a time, the full Moon seems to disappear as it changes color, darkens, and then reappears. Throughout time, people have had different ideas about what causes a lunar eclipse. Here are some of their ideas:
A) A nearby planet passes between the Earth and the Moon.
B) The Sun passes between the Earth and the Moon.
C) The Moon passes between the Sun and the Earth.
D) The Earth passes between the Sun and the Moon.
E) The clouds block out the Moon.
F) A nearby planet’s shadow falls on the Moon.
G) The Moon’s shadow falls on the Earth.
H) The Moon turns to the dark side and then back to the light side.
Which one is correct? Why?
The best answer is D: The Earth passes between the Sun and the Moon. A lunar eclipse occurs whenever the Moon passes through some portion of the Earth’s shadow. This occurs when the Sun, Earth, and Moon are in very close alignment, with the Earth in the middle. There is always a full Moon the night of a lunar eclipse. You will usually see a bright lunar disk gradually turn dark as it passes through Earth’s shadow—sometimes a coppery red color—for as long as an hour or more during a total eclipse. The Earth’s shadow has two parts, called the penumbra and the umbra. The umbra is much darker than the penumbra. When the entire Moon passes through the umbra, it is called a total lunar eclipse. When only part of the Moon passes through the umbra, it is called a partial lunar eclipse. And when the Moon goes through the penumbra, it is called a penumbral eclipse. In each of these types of eclipses, the Earth is always between the Sun and the Moon. Lunar eclipses (as well as solar eclipses) happen roughly every six months. A lunar eclipse is visible to anyone on Earth who would have otherwise seen the full Moon.
Five friends built a marble tower. The marble tower had a curved track. The track was designed so that the marbles would move down the track in a circular path. The track ended on the floor. Each friend predicted how he or she thought the marble would move when it rolled off the end of the track onto the floor. This is what they said:
Magda: “I think it will roll in circles.”
Soledad: “I think it will curve for a bit and then straighten out.”
Allen: “I think it will roll in one big curve.”
Keira: “I think it will roll in a straight line.”
Rafael: “I think it will zigzag for a little while.”
Who was right? Why?
The best answer is Keira’s: The marble leaving the track will travel in a straight line. This behavior is true of all objects: If no outside forces act on an object, the object will travel in a straight line at a constant speed. As the marble rolls down the marble tower’s spiral track, a force toward the center of the spiral (a centripetal force) caused by the outside wall keeps the marble rolling in a spiral path. When the marble leaves the end of the track, it is no longer in contact with the walls of the track. Without the track pushing on it, the marble no longer has a center-directed force acting on it that causes it to roll in a curved path. According to Newton’s first law, an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. Since there is no longer a center-directed, external force exerted by the walls of the circular track pushing on the marble, the marble rolls off the end of the track in a straight-line path across the floor. It will continue to do so until an outside force causes it either to change direction or slow down and stop.
Seeds sprout and eventually grow into young plants. Some friends were talking about what seeds need in order to sprout. Here's what they said:
Clark: "I think seeds only need air, warmth, and water."Keisha: "No, they definitely need air, warmth, water, sunlight, and fertilizer."
Ra'Niya: "You forgot that they need food and Earth's gravity too!"
Sean: "I think you're a little off - they need water, soil, air, food, sunlight, darkness, warmth, Earth's gravity, AND fertilizer to sprout!
Who do you most agree with and why?Seeds need water, air, and warmth.
Like all living things, the plant embryo inside a seed needs water, air, food, and warmth to carry out the life processes that will support its germination and growth. The young plant embryo needs food as its source of energy and building material for growth...but the food it needs is already contained within the seed in the form of a cotyledon, since a young sprout does not yet have the leaves to enable it to carry out photosynthesis!
Air is necessary for seeds to respire, and seeds must take in oxygen to use and release energy from their food. Seeds also require a warm temperature and water for the life-sustaining chemical reactions that take place in the cells of the young plant embryo to occur. However, some seeds, such as acorns, needs to go through a cold period before they germinate. Too much liquid water “drowns" seeds by preventing them from taking in oxygen and causes them to rot. Some seeds can sprout in humid air without the need for a moist surface. Hence, the right amount of water needs to be available. Seeds can sprout without soil as long as they have a source of moisture. Sunlight is not needed, as evidenced by the way many seeds germinate when covered by soil. Seeds have sprouted in microgravity in space. Gravity affects the ability of the sprout to send its early root structures downward, but seeds can sprout even in conditions were gravity is much less than on Earth. Fertilizers are not needed by seeds. They are used by plants once they have established roots and can take in these substances from the soil to contribute essential elements to the cells that make up their plant structures.
Five friends were camping in the north woods. It was a clear night with mild weather conditions. Sunset was at 9:14 p.m. Sunrise was at 5:22 a.m. The five friends wondered when it would be coldest as they slept under the stars. This is what they said:
Colin: “I think it will be coldest right after the Sun sets.”
Bono: “I think it will be coldest at midnight.”
Jeri: “I think it will be coldest around 3:00 a.m.”
Emma: “I think it will be coldest at the beginning of sunrise.”
Kit: “I think it will be coldest a few hours after sunrise.”
Who do you think is right? Why?
The best answer is Emma’s: “I think it will be coldest at the beginning of sunrise.” The coldest part of the day is generally right around the dawn, actually right after the sunrise while the Sun is still very low on the horizon. During the night, the Earth’s surface radiates the heat it has absorbed back out into space, allowing the temperature to drop. It does this during the day as well, but at night it has had the most time to radiate heat back to space without the incoming Sun’s warmth to offset or compensate for the heat loss