Download Assessment Year Review

Assessment
Year Review
Instructions
Please complete this assessment on your own. Answer each item by clicking on the correct
choice, then go on to the next item.
1) Which phase occurs when the moon is between the Earth and the sun?
A) full moon
B) new moon
C) quarter moon
D) harvest moon
Explanation:
The correct response is B. A new moon appears when the moon is between the Earth and sun, and the
illuminated part of the moon does not face the Earth.
2) What happens to the molecules as water freezes?
A) The water molecules stop moving.
B) The water molecules move faster.
C) The water molecules slow down.
D) The water molecules react chemically to form ice molecules.
Explanation:
The answer is C. As the temperature drops, the movement of the water molecules slows.
3) Heat always travels _______.
A) from low to high places
B) from high to low places
C) from warm to cool places
D) from cool to warm places
Explanation:
The correct answer is C. Heat always travels from warm places to cool places.
4) The process by which fast-moving molecules transfer their energy directly to
slower-moving molecules is called _______.
A) convection
B) radiation
C) sublimation
D) conduction
Explanation:
The correct answer is D. Conduction occurs when energy is transferred from fast-moving molecules directly to
slower-moving molecules.
5) A pot holder is useful for picking up hot objects because it is a good:
A) conductor.
B) insulator.
C) radiator.
D) refractor.
Explanation:
The answer is B. A pot holder is a good insulator because it does not conduct heat well.
6) Which of the following is the poorest conductor of heat?
A) copper
B) aluminum
C) air
D) steel
Explanation:
The correct answer is C. Metals are all good conductors of heat. Air is a poor conductor of heat, so it's a good
insulator.
7) What are the organelles that use sunlight to produce food in the process of
photosynthesis?
A) mitochondria
B) ribosomes
C) chloroplasts
D) vacuoles
Explanation:
C is the correct answer. Photosynthesis takes place in the chloroplasts of plant cells.
8) In a plant cell, which organelle is the site of photosynthesis?
A) mitochondria
B) chloroplast
C) endoplasmic reticulum
D) contractile vacuole
Explanation:
The correct answer is B. The chloroplast in plant cells is where photosynthesis takes place.
9) Identify which of the following best explains the transformation process in
photosynthesis.
A) Electrical energy is transformed into chemical energy.
B) Chemical energy is transformed into light energy.
C) Light energy is transformed into electrical energy.
D) Light energy is transformed into chemical energy.
Explanation:
The correct answer is D. Light energy from the sun is transformed into chemical energy by photosynthesis.
10) Photosynthesis could not occur without which of the following?
A) glucose
B) sunlight
C) oxygen
D) ozone
Explanation:
The correct answer is B. It is correct because photosynthesis energy from the sun.
11) Which substances are needed to make food in plants?
A) glucose and oxygen
B) oxygen and water
C) water and carbon dioxide
D) carbon dioxide and oxygen
Explanation:
The answer is C. Plants take in water and carbon dioxide to produce glucose and oxygen during photosynthesis.
12) Which phase takes place when the moon’s surface is not visible?
A) full moon
B) quarter moon
C) harvest moon
D) new moon
Explanation:
The correct response is D. A new moon appears when the moon is between the Earth and sun and its illuminated
part does not face the Earth.
13) Imagine living 100,000 years ago when unexpectedly, the Sun disappears from the sky.
The event just described is a _______________.
A) total solar eclipse
B) penumbra
C) total lunar eclipse
D) new moon
Explanation:
The correct answer is A. It is correct because as the moon revolves around the Earth and lines itself up perfectly
between the sun and Earth, the moon casts a shadow, a person standing in the shadow experiences a total solar
eclipse.
14) How are the Sun, Earth, and Moon aligned during a lunar eclipse?
A) Sun-Moon-Earth
B) Moon-Sun-Earth
C) Earth-Sun-Moon
D) Sun-Earth-Moon
Explanation:
D is the correct answer. It is correct because during a lunar eclipse, the Moon passes through the Earth's
shadow, and is positioned between the Sun and the Moon.
15) What does this diagram represent?
A) a lunar eclipse
B) a new moon
C) a gibbous moon
D) a solar eclipse
Explanation:
The diagram represents a lunar eclipse. A lunar eclipse takes place when Earth lines up between the Moon and
the Sun. As a result, Earth's shadow covers the Moon for a brief period. We are able to see Earth's shadow move
over the Moon during a lunar eclipse. The correct answer is A.
16) A solar eclipse occurs when the _________________.
A) Earth is between the sun and the moon
B) sun is between the Earth and the moon
C) moon is between the Earth and the sun
D) sun is blocked by the Earth
Explanation:
The correct answer is C. When the moon blocks the path of the sun's light to the Earth, a solar eclipse takes
place.
17) When the Moon passes through the Earth's shadow, what has occurred?
A) a new moon
B) a solar eclipse
C) a full moon
D) a lunar eclipse
Explanation:
D is the correct answer. It is correct because when the Moon passes through the Earth's shadow, and the Sun,
Earth and Moon are positioned in a nearly straight line, a lunar eclipse has occurred.
18) What is the darkest portion of the Moon's shadow during an eclipse called?
A) penumbra
B) sunspot
C) umbra
D) maria
Explanation:
The correct answer is C. It is correct because the name given to the shadow cast by the moon as it centers itself
between the Earth and Sun causing an eclipse is the umbra, only those standing within the umbra experience a
total solar eclipse.
19) Dog fur often picks up tiny prickly structures, which may grow into a new plant when
they fall to the ground. What are these structures?
A) tubers
B) seeds
C) leaves
D) stems
Explanation:
The correct answer is B. Specialized seeds that stick to dog fur may grow into new plants in other places.
20) Plants produce seeds so they can do what?
A) discourage animals from eating their fruit
B) reproduce
C) provide animals with food
D) maintain beneficial relationships with insects
Explanation:
The correct answer is B. Every seed is a potential new plant waiting for germination.
21) When plants undergo photosynthesis, what gas do they release into the air?
A) carbon dioxide
B) nitrogen
C) sulfur dioxide
D) oxygen
Explanation:
The correct answer is D. It is correct because oxygen is released by plants during photosynthesis.
22) Which of the following is the reason for plants being able to make their own food
through photosynthesis?
A) Plants rely on other organisms for food.
B) Plants move about to obtain nutrients.
C) Plants cannot move to obtain food.
D) Plants are capable of independent movement
Explanation:
The correct answer is C. Plants cannot move to obtain food so it is important for them to be able to make their
own food through photosynthesis.
23) Which moon phase occurs when the entire surface of the moon facing the Earth is
illuminated?
A) full moon
B) quarter moon
C) half moon
D) harvest moon
Explanation:
The correct response is A. The full moon appears when the sun and moon are on opposite sides of the Earth.
24) In seed-producing plants, pollen grains contain:
A) sperm
B) eggs
C) seeds
D) embryos
Explanation:
The correct response is A. In seed-producing plants, pollen grains contain sperm, or male gametes.
25) Plants use water for photosynthesis. How does that water get into the plant?
A) from rain on the leaves through the stomata
B) through the roots
C) from moisture in the air through pores in the leaf
D) through the stems
Explanation:
The answer is B. The roots of a plant take in water and nutrients from the soil.
26) Which plant function do flowers serve?
A) reproduction
B) photosynthesis
C) food storage
D) collecting water and minerals
Explanation:
The correct answer is A. The function of flowers is reproduction.
27) Identify how seeds relate to reproduction.
A) They are products of asexual reproduction in plants.
B) They are products of sexual reproduction in plants.
C) They are contributors to asexual reproduction in plants.
D) They are contributors to sexual reproduction in plants.
Explanation:
The correct answer is B. Seeds are the products of sexual reproduction, of a sperm fertilizing an egg.
28) Identify the primary function of fruit.
A) seed nourishment
B) seed protection
C) seed production
D) seed dispersion
Explanation:
The correct answer is D. When an animal eats fruit, the seeds are either spit out or swallowed and deposited in
the feces. Either way, the seeds end up moving away from the plant that produced them.
29) The tectonic plates are floating on material that is moving in the Earth's __________.
A) mesosphere
B) mantle
C) outer core
D) inner core
Explanation:
The correct answer is B. The tectonic plates are floating on the part of the mantle that is plastic-like and able to
flow.
30) A plate boundary in which no new crust is made or destroyed is a:
A) divergent boundary
B) convergent boundary
C) recumbant boundary
D) transform boundary
Explanation:
The correct answer is D. Plates slip past each other at transform boundaries.
31) Heat from inside the Earth is known as ___ energy.
A) nuclear
B) geothermal
C) chemical
D) mechanical
Explanation:
The correct answer is B. Heat from inside the Earth is geothermal energy.
32) Rift valleys often occur along what type of plate boundary?
A) divergent
B) convergent
C) transform
D) inactive
Explanation:
The correct answer is A. Rift valleys often form where plates move apart.
33) The movement of tectonic plates is caused by:
A) convection currents in the mantle.
B) heat in the inner core.
C) radiation from the sun.
D) strong global winds.
Explanation:
The correct answer is A. Convection currents in the hot, plastic-like mantle carry the plates of the lithosphere
above them.
34) What is a waning moon?
A) another name for full moon
B) another name for a new moon
C) an increase in the visible surface of the moon as the days progress
D) a decrease in the visible surface of the moon as the days progress
Explanation:
The correct response is D. A waning moon is the decreasing illumination from a full moon to a new moon.
35) When a tectonic plate with continental crust crashes into a plate with oceanic crust, the
ocean plate slides under the continental plate. A region where oceanic plates are forced
downward is called a:
A) strike-slip fault
B) divergent boundary.
C) transform boundary.
D) subduction zone.
Explanation:
The answer is D. A subduction zone occurs when an oceanic plate sinks down under a continental plate.
36) Convergent plate boundaries ________.
A) pull apart
B) slide past each other
C) collide
D) do not move
Explanation:
The correct response is C. Converge means to come together.
37) A chief cause of the formation of metamorphic rock is __________.
A) weather
B) cosmic rays
C) Earth's rotation
D) plate motion
Explanation:
The correct answer is D. Plate motion heats and squeezes rock, resulting in metamorphism.
38) Which of the following is found at a divergent plate boundary?
A) the San Andreas Fault.
B) the Himalayan Mountains.
C) the Marianas Trench.
D) the Mid-Atlantic Ridge
Explanation:
The correct response is D. The Mid-Atlantic Ridge is a divergent boundary, where two plates are moving apart.
39) Where tectonic plates diverge, __________.
A) new rock comes to the Earth's surface
B) folded mountains form
C) strike-slip faults form
D) one plate dives beneath another
Explanation:
The correct answer is A. At divergent boundaries the tectonic plates move apart. This allows magma to move to
the surface where it cools to form new igneous rock.
40) The tectonic plates move at about the same rate as __________.
A) the Earth rotates
B) your fingernails grow
C) the hour hand on a clock moves
D) the minute hand on a clock moves
Explanation:
The correct answer is B. The plates move at about the rate that your fingernails grow, or about one inch per year.
41) The gravity of the Sun and the Moon together cause an ocean motion called ___________.
A) tides
B) currents
C) waves
D) tsunamis
Explanation:
The correct answer is A. Tides are caused by the gravitational pull of the Sun and Moon.
42) Most coastlines on the Earth experience how many tides each day?
A) two high tides and two low tides
B) two high tides and one low tide
C) one high tide and two low tides
D) one high tide and one low tide
Explanation:
The correct answer is A. Most coastlines experience two high tides and two low tides each day.
43) The force which is responsible for keeping the planets in their orbit also plays a role in
the occurrence of tides on Earth. The force is _______________.
A) magnetism
B) rotation
C) friction
D) gravity
Explanation:
The correct response is D. It is correct because the gravitational attraction between the Earth, Moon, and Sun
causes tides.
44) Which factor listed below has no affect on Earth's seasons?
A) the tilt of the Earth's axis
B) the revolution of the Earth around the sun
C) the revolution of the Moon around the Earth
D) the energy that the Earth receives from the Sun
Explanation:
The correct response is C. It is correct because the revolution of moon does not affect occurrence of seasons on
the earth.
45) What is a waxing moon?
A) an increase in the visible part of the moon as the days progress
B) a decrease in the visible part of the moon as the days progress
C) another name for full moon
D) another name for new moon
Explanation:
The correct response is A. A waxing moon is the increasing illumination from a new moon to a full moon.
46) Which season is it in the Southern Hemisphere when the sun's rays strike most directly?
A) spring
B) summer
C) autumn
D) winter
Explanation:
The correct answer is B. The sun's rays are most direct in the summer.
47) What is the movement of an object in space spinning on its axis?
A) rotation
B) revolution
C) orbiting
D) parallelism
Explanation:
The correct answer is A. Rotation is an object turning around a center or a shaft. Revolution is moving around
another object.
48) When is the Earth's axis tilted neither toward nor away from the Sun?
A) when the Earth is closest to the Sun
B) when the Earth is farthest from the Sun
C) during both equinoxes
D) during both solstices
Explanation:
The correct answer is C. Earth's axis is tilted neither toward nor away from the Sun during both equinoxes.
49) In the Northern Hemisphere the sun is highest in the sky during the _____.
A) vernal equinox
B) summer solstice
C) autumnal equinox
D) winter solstice
Explanation:
The correct answer is B. In any given hemisphere, the sun is highest in the sky on the summer solstice.
50) During the warmer seasons such as summer, the sun's rays hit the Earth ______________.
A) indirectly
B) sparingly
C) more directly
D) less frequently
Explanation:
The correct response is C. In summer, the sun's rays strike the Earth more directly.
51) When an object orbits another object, it is said to ____________.
A) spin
B) pendulum
C) rotate
D) revolve
Explanation:
The correct answer is D. To revolve means to move around another object.
52) Use the diagram to answer the question below.
At which positions will the Earth
have spring and fall?
A) positions 1 and 2
B) positions 2 and 4
C) positions 3 and 4
D) positions 4 and 1
Explanation:
The correct response is B. It is correct because at position 2 and 4, the Sun is directly overhead at the equator
and an equal amount of solar energy is received in both hemispheres by Earth, so it will be spring or fall on
Earth.
53) What is the main reason that summer is warmer than winter?
A) The tilt of Earth's axis results in more direct radiation from the sun in the summer.
B) Earth rotates slower around the Sun during the summer than it does the rest of the year.
C) Earth is closer to the sun during the summer than during the other seasons.
D) Earth's magnetic field is stronger in the summer than it is the rest of the year.
Explanation:
The correct answer is A. It is correct because if a line were drawn perpendicular to the plane of Earth's orbit you
would find the Earth tilted on a 23.5 degree angle, and it is this tilt that allows the hemisphere which is tilted
toward the Sun longer hours of sunlight causing warmer summer like temperatures.
54) What season is it in Utah when the southern hemisphere of the Earth is tilted toward the
Sun?
A) spring
B) summer
C) winter
D) fall
Explanation:
The correct answer is C. The answer is correct because when the southern half of the Earth is tilted toward the
Sun it is summer there. Utah would be in that part of the Earth tilted away from the Sun meaning it's winter there.
55) The main cause of the seasons is ___________.
A) variations in the sun's energy
B) the changing distance of the Earth from the sun.
C) the changing speed of Earth's rotation.
D) the Earth's axis is tilted.
Explanation:
The correct answer is D. The angle of tilt of Earth's axis remains the same as Earth orbits the sun.
56) Which statement below best explains why ice cubes melt when they are placed in a glass
of water?
A) A chemical change occurs which causes the ice molecules to break up into hydrogen and oxygen.
B) Pressure from the water squeezes the ice cubes, making them very small.
C) Heat is transferred from the ice cubes to the water.
D) Heat is transferred from the water to the ice cubes.
Explanation:
The correct answer is D. Heat is transferred from the water to the ice, causing the ice to change into liquid
water.
57) Because the sun's rays strike different parts of the Earth at different angles throughout
the year, we have _________.
A) seasons
B) day and night
C) tides
D) years
Explanation:
The correct answer is A. The sun's rays strike different parts of the Earth at different angles in different seasons.
58) Which number in the diagram below shows the relationship between the sun and Earth
when it is Summer in North America?
A) Number 1
B) Number 2
C) Number 3
D) Number 4
D) Number 4
Explanation:
The answer is A. When the north end of the Earth's axis is tilted toward the sun, it is Summer in the Northern
Hemisphere.
59) What is the smallest part of an element that still has the properties of that element?
A) an atom
B) a compound
C) a molecule
D) a nucleus
Explanation:
60) Which of these particles make up atoms?
A) protons, neutrons and electricity
B) protons, nucleus and electrons
C) neutrons, positrons and electrons
D) protons, neutrons and electrons
Explanation:
61) What is the definition of an atom?
A) an incomplete bit of matter
B) largest complete bit of matter
C) smallest complete bit of matter
D) A fragment of complete matter
Explanation:
62) What do the small particles protons ,neutrons, and electrons compose?
A) cells
B) atoms
C) space
D) electricity
Explanation:
63) Which processes are primarily responsible for the formation of soil?
A) volcanic activity
B) weathering and decomposition of organisms
C) the impact of meteorites
D) earthquakes
Explanation:
The correct answer is B. Weathering and decomposition of organisms are primarily responsible for the
formation of soil.
64) A mixture of rock, pieces of mineral, organic matter, bacteria and water is called ________.
A) clay
B) soil
C) outwash
D) slush
Explanation:
The correct answer is B. It is correct because soil forms from layers of decomposed plants, animals, rock and
minerals that break apart into pieces due to weathering.
65) The minerals present in the soil of an area will depend on the __________.
A) climate
B) altitude
C) vegetation
D) parent rocks
Explanation:
The correct response is D. It is correct because the kind of minerals found in an area will depend on the type of
rocks that have undergone weathering to form the soil.
66) On the moon, an astronaut's weight would not be the same as on Earth because:
A) the moon has no gravity.
B) the moon has no air.
C) the moon's gravity is less than Earth's.
D) the moon's gravity is greater than Earth's.
Explanation:
The correct answer is C. The force of gravity on the moon is about one-sixth that on Earth.
67) Suppose a 10 mL beaker and a 100 mL beaker are both filled with water, and that the
water in both beakers is the same temperature. Which statement below about the water in
the two beakers is true?
A) The two beakers of water contain equal amounts of heat.
B) The larger beaker of water contains more heat than the smaller beaker.
C) The smaller beaker of water contains more heat than the larger beaker.
D) It is not possible to determine which beaker of water contains the most heat because heat cannot be
measured.
Explanation:
The correct answer is B. Since both beakers of water are the same temperature, the larger beaker must contain
more heat since it contains more water at that temperature.
68) What is the name of the envelope of gases that surrounds the Earth?
A) chromosphere
B) atmosphere
C) lithosphere
D) hydrosphere
Explanation:
The correct answer is B. Atmosphere is air, hydrosphere is water, lithosphere is rock.
69) The Earth is the only planet in our solar system known to have _______.
A) craters
B) life
C) polar caps
D) clouds
Explanation:
The correct answer is B. Only Earth is known to have life. Mars has craters and polar caps; many planets have
clouds.
70) An astronaut who traveled from the Earth to the moon would ___________.
A) be weightless.
B) have somewhat more weight than on Earth.
C) have somewhat less weight than on Earth.
D) have the same weight as on Earth.
Explanation:
The correct answer is C. On the moon the astronaut would weigh about one-sixth the Earth weight.
71) Mercury, Venus, Earth, and Mars are all inner planets. Identify one unique characteristic
of Earth that makes life possible here.
A) Earth is rocky and dense.
B) Earth rotates on its axis.
C) Earth has liquid water.
D) Earth has craters.
Explanation:
The correct answer is C: Earth is the only planet to have liquid water.
72) Which part of Earth is believed to be in the liquid state?
A) crust
B) mantle
C) outer core
D) inner core
Explanation:
The correct answer is C. Certain seismic waves will not travel through a liquid. These same waves will not pass
through the outer core of the Earth; therefore, it is believed that the outer core is liquid.
73) Name the instrument that measures and records earthquake vibrations.
A) spectrograph
B) seismograph
C) barograph
D) thermograph
Explanation:
The correct answer is B. Seismographs record the vibrations, or seismic waves, produced by earthquakes.
74) Plate movement, earthquakes, and volcanoes are a result of convection currents in which
layer of the Earth?
A) inner core
B) outer core
C) lithosphere
D) mantle
Explanation:
The correct answer is D. Convection currents in the hot, plastic-like rock of the mantle, cause movement of the
plates, which results in earthquakes and volcanoes.
75) Identify the four layers of the Earth.
A) crust, mantle, outer core, inner core
B) land, sea bottom, outer core, inner core
C) soil, crust, outer core, inner core
D) crust, subduction zone, outer core, inner core
Explanation:
76) Earth's crust is divided into:
A) upper crust and lower crust
B) mountain crust and valley crust
C) continental crust and oceanic crust
D) eastern crust and western crust
Explanation:
The correct answer is C. The Earth's crust is divided into continental crust and oceanic crust.
77) Which two layers of the Earth are believed to be mostly metallic in composition?
A) crust and mantle
B) crust and outer core
C) mantle and inner core
D) outer core and inner core
Explanation:
The correct answer is D. Both the outer and inner core are believed to be composed primarily of iron and nickel.
78) The total kinetic energy of the molecules in a substance is correctly referred to as:
A) heat
B) density
C) temperature
D) solubility
Explanation:
The correct response is A. Heat is the total kinetic energy of all of the molecules in a substance.
79) During cellular respiration, oxygen is used and ___________ are produced.
A) nitrogen and water
B) glucose and carbon dioxide
C) carbon dioxide and water
D) nitrogen and carbon dioxide
Explanation:
The correct answer is C. The correct answer is C because Carbon Dioxide is the waste product of cellular
respiration.
80)
take place?
In which organelle does the process of cellular respiration
A) mitochondria
B) chloroplast
C) vacuole
D) ribosome
Explanation:
The answer is A. Cellular respiration takes place in the mitochondria.
81) The process by which a cell releases energy from food is called __________.
A) respiration
B) photosynthesis
C) digestion
D) osmosis
Explanation:
The answer is A. Energy is released from food molecules during cellular respiration.
82) Radiant energy travels in the form of:
A) electromagnetic waves.
B) fast moving molelcules.
C) disturbances in solids, liquids, or gases
D) chemical reactions.
Explanation:
The correct answer is A. Radiant energy travels in the form of electromagnetic waves.
83) When you stand in front of a fire you feel warm. The heat that you feel is in the form of:
A) ultraviolet radiation.
B) radio waves.
C) infrared radiation.
D) hot molecules.
Explanation:
The correct answer is C. When you stand in front of a fire, the heat that you feel is infrared radiation.
84) Energy that travels as electromagnetic waves is called:
A) convection
B) radiation
C) conduction
D) condensation
Explanation:
The correct answer is B. Radiation is energy that travels through space as electromagnetic waves.
85) Which part of the electromagnetic spectrum is visible?
A) a tiny part of it
B) all of it
C) none of it
D) most of it
Explanation:
The correct answer is A. Visible light makes up a small part of the electromagnetic spectrum.
86) What property of visible light accounts for the colors we see?
A) speed
B) amplitude
C) frequency
D) charge
Explanation:
The correct response is C. The frequency of visible light determines its color.
87) Which part of an object determines the colors of light it reflects?
A) its interior
B) its top
C) its surface
D) its bottom
Explanation:
The correct response is C. An object's surface determines the colors of light that it reflects.
88) Which makes an object blue?
A) The object absorbs blue light.
B) The object refracts blue light.
C) The object transmits blue light.
D) The object reflects blue light.
Explanation:
The correct answer is D. An object that reflects blue light will appear blue.
89) When a thermometer is placed in a substance, what is it actually measuring?
A) heat
B) temperature
C) pressure
D) density
Explanation:
The correct answer is B. The thermometer is measuring the temperature, or average kinetic energy of the
molecules in the substance.
90) Green plants appear green because they__________.
A) absorb green light and reflect all other colors
B) refract green light and reflect all other colors
C) reflect green light and absorb all other colors
D) transmit green light and reflect all other colors
Explanation:
The correct answer is C. The pigment chlorophyll in the plants reflects green light and absorbs the other colors.
91) What determines an object's color?
A) The color of an object is based on the light it reflects.
B) The color of an object is based on the light it absorbs.
C) The color of an object is based on the light it transmits.
D) The color of an object is based on molecular bonds.
Explanation:
The correct answer is A. The color of an object is based on the light it reflects.
92) Heat transfer by movement in a fluid, like air or water, is called _____.
A) convection
B) conduction
C) radiation
D) absorption
Explanation:
The correct answer is A. Convection involves heat transfer by movement in a fluid.
93) Which statement is true about a convection current in water?
A) Both warm and cold water rise.
B) Both warm and cold water sink.
B) Both warm and cold water sink.
C) Warm water sinks and cold water rises.
D) Cold water sinks and warm water rises.
Explanation:
The correct answer is D. In a convection cell, cold water, which is denser than warm water, sinks and pushes the
warm water upward.