Science Final Study Guide
Order the steps of the Scientific method in the correct order.
1. Observe the natural world and ask a scientific question. 2. Research the scientific question being asked. 3. Develop a hypothesis. 4. Design and implement a plan. 5. Collect and analyze data. 6. Accept or reject the original hypothesis.
Which objective would be used to locate a specimen on a microscope slide?
4x
Quantitative data
A count or a measurement recorded during an experiment.
Controlled variable
A factor that is held constant for all the experimental groups in an experiment.
Dependent variable
A factor that is measured as data in an experiment.
Independent variable
A factor that the experimenter changes between the different experimental groups.
A vacuum is an area with no matter in it, not even air. If you were in a vacuum, you could not hear a sound, even if it were made right next to you. Why is this? Remember to think of the sound as a mechanical wave.
A mechanical wave needs a medium to travel through. Otherwise, it cannot transfer energy. In a vacuum, there is no medium for the wave to travel through. Since sound is a mechanical wave, it cannot travel in a vacuum, so you would not hear it.
Give 2 examples of a wave diffracting.
A wave in a lake moving around a boat or a sound wave traveling through an open window.
Decrease Chemical Potential Energy:
Add water (dilute it with water), decrease the heat.
Caroline tested the rate of evaporation for four liquids by placing 100 mL of each liquid into separate Petri dishes. She waited 24 hours before measuring the amount of liquid left in the dish. Which description represents quantitative data collected by Caroline?
After 24 hours, 15 mL of each liquid into four different containers.
Sam wished to investigate how fertilizer run-off affects the growth of algae in freshwater lakes and streams. He set his experiment up in this way. He placed 900mL of water into each of five 1000mL glass beakers. To each beaker he added 5mL of water from an aquarium which contained a large concentration of algae. The beakers were placed under a grow light which was timed to provide 12 hours of light each day. Liquid fertilizer was added to the beakers in the following amounts: Beaker A- 8ml of fertilizer, Beaker B- 6ml of fertilizer, Beaker C- 4ml of fertilizer, Beaker D- 2ml of fertilizer, and Beaker E- no fertilizer. Each week a random sample from each of the beakers was examined under a microscope to get a count of the number of algae cells present. What is the independent variable in this experiment?
Amount of fertilizer.
Sam wished to investigate how fertilizer run-off affects the growth of algae in freshwater lakes and streams. He set his experiment up in this way. He placed 900mL of water into each of five 1000mL glass beakers. To each beaker he added 5mL of water from an aquarium which contained a large concentration of algae. The beakers were placed under a grow light which was timed to provide 12 hours of light each day. Liquid fertilizer was added to the beakers in the following amounts: Beaker A- 8ml of fertilizer, Beaker B- 6ml of fertilizer, Beaker C- 4ml of fertilizer, Beaker D- 2ml of fertilizer, and Beaker E- no fertilizer. Each week a random sample from each of the beakers was examined under a microscope to get a count of the number of algae cells present. Which of the following is NOT a controlled variable in this experiment?
Amount of fertilizer.
Draw and label 3 different diagrams, which show when an object has the greatest and least gravitational potential energy:
At the top is the greatest and at the bottom is the least.
Barium + Fluorine
Barium Fluoride = BaF2
Sam wished to investigate how fertilizer run-off affects the growth of algae in freshwater lakes and streams. He set his experiment up in this way. He placed 900mL of water into each of five 1000mL glass beakers. To each beaker he added 5mL of water from an aquarium which contained a large concentration of algae. The beakers were placed under a grow light which was timed to provide 12 hours of light each day. Liquid fertilizer was added to the beakers in the following amounts: Beaker A- 8ml of fertilizer, Beaker B- 6ml of fertilizer, Beaker C- 4ml of fertilizer, Beaker D- 2ml of fertilizer, and Beaker E- no fertilizer. Each week a random sample from each of the beakers was examined under a microscope to get a count of the number of algae cells present. Which of the following is the control group for this experiment?
Beaker E.
Calcium + Chlorine
Calcium Chlorine = CaCl2
What will two balanced forces do to one another?
Cancel each other out.
Students gathered data to analyze their water consumption. The table shows the range of averages for the class. The students discussed the data to reach conclusions. Which statement from their discussion describes skepticism about the data?
Carlos wonders if the dishwashing data is accurate since the range is so large.
A forest fire destroys trees in a large area. The forest rangers use the burned area to study the effect on different types of grasses on soil erosion. they choose ten plots of ground that are the same size. Each of these plots receives the same amount of sun. Each of these plots also has the same kind of soil and the same slope. The rangers plant each with a different type of grass. Measurements of soil erosion are made every week for the entire summer. What hypothesis is being tested in this study?
Certain types of grasses have a greater effect on reducing soil erosion than others.
Cesium + Bromine
Cesium Bromide = CsI
Increase Chemical Potential Energy:
Combine the chemicals and the react, catalysts: enzymes, add heat.
The graph below shows the results of a controlled experiment which measured the population of one type of species of bacteria which had been grown in four containers under identical conditions. Antibiotics are chemicals that kill bacteria. Some bacteria are resistant to antibiotics. Over time, bacteria resistant to antibiotics reproduce and create populations of bacteria that are not affected by antibiotics. Which container in the experiment was considered the control group?
Container with no antibiotic added.
How do you find the frequency of a wave?
Count the number of waves that pass a specified point in a certain amount of time.
Draw a transverse wave diagram, and label all parts:
Crest, wavelength, amplitude, trough,
Qualitative data
Descriptions or observations recorded during an experiment.
What type of interference will make two speakers sound much quieter in certain parts of a room?
Destructive interference
Patrick and SpongeBob love to blow bubble! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubble made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5oz. of Super Bubble Soap and 5oz. of water, while the other was made with the same amount of water and 5oz. of regular buble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart. What is the independent variable?
Different brands/types of Bubble Soap.
When you see your shadow on the ground, you are seeing the light waves do what around you?
Diffraction of the light around you
What are mechanical waves caused by?
Disturbances in a medium.
What is it called when a sound wave hits a barrier and bounces back?
Echo / Reflection
Newton's Third Law of Motion:
Every action has an equal and opposite reaction.
List the signs of a Chemical Change:
Evidence: color change, temperature change, gas form (odor bubbles), forms solid (precipitate), light given off.
A well designed experiment can only have one dependent variable.
False
An experiment is successful if it proves the hypothesis to be correct:
False. A hypothesis is never a "problem". A hypothesis is simply supported or not supported.
Newton's Second Law of Motion (States that):
Force= Mass x Acceleration
How does friction relate to two surfaces that are in motion, and in contact with one another?
Friction resists motion.
Four different lab groups collected data from an experiment that they conducted in class. Which group collected quantitative data during the experiment?
Group N saw a cirrus cloud at 50km and a cumulus cloud at 100km.
Sarah wanted to find out if temperature has an effect on the growth of bread mold. SHe grew mold in nine Petri dishes containing the same amount and type of nutrients. Three were kept at 0 C, three were kept at 90 C, and three were kept at 27 C. The containers were examined and the growth of the bread mold was recorded each Friday for five weeks. The dependent or responding variable is:
Growth of bread mold.
What is the error in this experiment? Bill tests wheels on skateboards to see which is fastest. He pushes Bob who has Zippy wheels and measures the distance he travels. Next he pushes Tim with Snappy wheels and measures. Lastly, he pushes Jim on Turbo wheels and measures the distance he travels. They all do the experiment on the same road. Tim goes the farthest.
He didn't use the same person for each board. So he has two independent variables.
SpongeBob loves to garden and wants to grow lots of pink flowers for his pal Sandy. He bought a special Flower Power fertilizer to see if it will help his plants produce more flowers. He plants three plants of the same size in separate containers with the same amount and type of potting soil. He places one plant in a sunny window and waters it every day with fertilized water. He places the second plant in a more shady window and waters it every day with fertilized water. He places the third plant in a dark closet and waters it every day with plain water. What did Spongebob do wrong in the experiment?
He has too many independent variables.
Suzie Q wants to know the effect of different colors of light on the growth of plants. She believes that plants can survive best in white light. She buys 5 ferns of the same species, which are all approximately the same age and height. She places one in white light, one in blue light, one in green light, one in red light, and one in the closet. All of the ferns are planted in Miracle-Grow and given 20 mL of water once a day for 2 weeks. After 2 weeks, Suzie observes the plants and makes measurements.
Hypothesis: If a plant is placed in white light, then it will grow taller than plants placed in other colors of light. Independent variable: different color lights. Dependent variable: measurement of plant growth. Control group: plant in closet (no light) Experimental group: ferns places in blue, green, white, and red lights. Constants: same species fern, same age fern, same height fern, same Miracle- Grow, etc.
Some chickens lay an egg every day. Other chickens produce few eggs. A study is planned to examine factors that might affect the number of eggs produced by chickens. Which of the following is NOT a suitable hypothesis for the study?
If more eggs are produced by chickens, then they lose more weight.
what must you find out after conducting an experiment and collecting data?
If the results support your hypothesis.
Sarah wanted to find out if temperature has an effect on the growth of bread mold. SHe grew mold in nine Petri dishes containing the same amount and type of nutrients. Three were kept at 0 C, three were kept at 90 C, and three were kept at 27 C. The containers were examined and the growth of the bread mold was recorded each Friday for five weeks. Which of the following is her hypothesis?
If the temperature changes, then the amount of bread mold will change.
How do forces cause a wave?
It disturbs the particles of the medium (move particles of medium from "rest position")—particles air, water, rock, etc.
How does the level of dissolved oxygen change between Week 1 and Week 6?
It fluctuates dramatically.
How does the level of phosphates change between Week 1 and Week 5?
It fluctuates dramatically.
What does it mean when a wave is refracting?
It is BENDING, because it's moving from one medium to a different medium—ex: Light Waves travel at different speeds through different mediums (air vs. water):
Choose a type of wave that we made during the wave lab in class. Draw a picture of the wave that was made and describe what type of wave it was and how the wave was made. Show in the picture the direction of disturbance and direction of the wave. Be sure to include how you know whether it is a transverse or a longitudinal wave.
Just draw the wave and do what its asking you to do...
Josephine is heating some test tubes with chemicals in them during a laboratory activity. Which is a safety Josephine should follow when heating liquids in the test tubes?
Keep the electrical cord of the hot plate away from water and the heating surface.
Potential energy can be converted into (blank) energy, and kinetic energy can be converted into (blank) energy.
Kinetic (first blank) potential (second blank)
Newton's first law of motion
Law of Inertia--- an object at rest tends to stay at rest until acted upon by an outside force. An object in motion tends to stay in motion at same speed and direction until acted upon by an outside force.
A wave made by a moving rope, a wave made by dipping your hand in water, (blank) and ocean waves are all example of what type of wave?
Light Waves (blank) and Transverse Waves
Lithium + Sulfur
Lithium Sulfide = Li2S
Patrick and SpongeBob love to blow bubble! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubble made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5oz. of Super Bubble Soap and 5oz. of water, while the other was made with the same amount of water and 5oz. of regular buble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart. What is the dependent variable?
Measurement of diameters of bubbles.
You want to determine if a new medication diet will help rats lose weight. What is the dependent variable?
Measuring the weight loss
Which tools can be used for collecting and analyzing data in science?
Meter stick, stopwatch, scale, computer
Zoe is studying plant cells and wants to view the nucleus of an onion cell. Which tool would enable Zoe to view the nucleus most clearly?
Microscope
Faith uses color filters to study how they block certain wavelengths of light and transmit others. She looks at the different colored objects with help of the color filters. What safety measure should she follow to conduct a good investigation?
Never look through the color filter with bare unprotected eyes.
You walk through a heavily overgrown field on your way to a wooded area. The weeds and grasses are about a foot high. The next day you develop an itchy skin rash on your face. You conclude that the rash developed because you cut through the heavily overgrown area. You will not go into the woods again. Is the above concern correct?
No it is an illogical conclusion.
An experiment is conducted to determine what physical properties identify a metal. One part of the experiment tested the melting point of a substance. An iron nail, a copper penny, and a piece of lead pipe were heated in an oven at 250 degrees Celsius. None of the metals showed any change. The conclusion, based on the experimental data, is that all metals have a melting point above 250 degrees Celsius. Is the above conclusion correct?
No it is an overgeneralization.
Sam wished to investigate how fertilizer run-off affects the growth of algae in freshwater lakes and streams. He set his experiment up in this way. He placed 900mL of water into each of five 1000mL glass beakers. To each beaker he added 5mL of water from an aquarium which contained a large concentration of algae. The beakers were placed under a grow light which was timed to provide 12 hours of light each day. Liquid fertilizer was added to the beakers in the following amounts: Beaker A- 8ml of fertilizer, Beaker B- 6ml of fertilizer, Beaker C- 4ml of fertilizer, Beaker D- 2ml of fertilizer, and Beaker E- no fertilizer. Each week a random sample from each of the beakers was examined under a microscope to get a count of the number of algae cells present. What is the dependent variable in this experiment?
Number of algae cells.
Give the chemical formula for the Hydroxide Ion:
OH-
How many independent variables are permitted in a controlled experiment?
Only one
GPE Formula
PE = mass x gravity x height
Explain the difference between a Chemical change and a Physical change (+Examples)
Physical change- same substance before and after- different phase or appearance. Chemical change- different substance/ new substance formed. Example- Ice Melt: physical change Rusting Metal: chemical change
Natalie wants to determine how different concentrations of fertilizer affect plant growth. the table shows the data for her experiment at the end of 6 weeks. What conclusion does the data support?
Plant growth increases at certain concentrations but can be harmful in high concentrations.
Science equipment is often used to take measurements during an experiment. Which measurement would be taken using this instrument (barometer)?
Pressure
Describe the characteristics of an Acid, and what happens when it is mixed with water:
Produces hydrogen ions in water. Tastes sour, corrodes metals, good electrolytes, has a pH less than 7.
Describe the characteristics of a Base and what happens when it is mixed with water:
Produces hydroxide ions in water. Tastes bitter, chalky, feels soapy/ slippery, electrolytes, has a pH greater than 7.
A student states that the graduated cylinder contains 150 mL of water. Which best describes this statement?
Quantitative observation.
You want to determine if a new diet medication will help rats to lose weight. What factors should you keep the same throughout the experiment for both sets of rats?
Rats and the food they eat
A straw in a glass of water appears to be broken or split, what is this caused by?
Refraction
What is the control in this experiment? Bob wants to figure which nonsecone works best on a rocket. He puts a pointed nosecone on rocket A, a round nosecone on rocket B, and no nosecone on rocket C. He launches them in his backyard and again in an open field.
Rocket C
How can an earthquake break and bend a road far away from the Earthquakes center?
Seismic waves transfer energy over a great distance
Practice balancing chemical equations:
SiO2 + 3C + SiC + 2CO
Sodium + Boride
Sodium Boride = NaBr
A (blank) is an example of what type of wave?
Sound Wave (blank) and Longitudinal Wave / Compressional Wave
Patrick and SpongeBob love to blow bubble! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubble made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5oz. of Super Bubble Soap and 5oz. of water, while the other was made with the same amount of water and 5oz. of regular buble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart. Calculate the average diameter for each bubble solution.
Super Bubble = 15.1 cm Regular Soap = 11.5 cm
Patrick and SpongeBob love to blow bubble! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubble made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5oz. of Super Bubble Soap and 5oz. of water, while the other was made with the same amount of water and 5oz. of regular buble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart. What did the Super Bubble ads claim?
Super Bubbles will be twice as big as regular bubbles
Sarah wanted to find out if temperature has an effect on the growth of bread mold. SHe grew mold in nine Petri dishes containing the same amount and type of nutrients. Three were kept at 0 C, three were kept at 90 C, and three were kept at 27 C. The containers were examined and the growth of the bread mold was recorded each Friday for five weeks. The independent or manipulated variable is:
Temperature of the containers.
What is the independent variable in the following experiment? Bill wants to figure out what type of battery works best. He buys Brand A, Brand B, Brand C. He gets three identical light bulbs and hooks the batteries up to them. After this, he puts them in the dishwasher for 20 minutes. He keeps track of the bulbs until they burn out. Bulb A burns out after 6 hours, Bulb B burns out after 6.5 hours, and Bulb C burns out after 8 hours.
The IV is the type of battery. Independent variable what is tested.
A forest fire destroys trees in a large area. The forest rangers use the burned area to study the effect on different types of grasses on soil erosion. they choose ten plots of ground that are the same size. Each of these plots receives the same amount of sun. Each of these plots also has the same kind of soil and the same slope. The rangers plant each with a different type of grass. Measurements of soil erosion are made every week for the entire summer. What is the depending or responding variable in this study?
The amount of soil erosion.
Mark wanted to see what would happen to an inflated balloon that was put into the freezer for several minutes and then removed. The table shows the results of his experiment at several points in time. What would happen to the balloon if it was left in the freezer for 7 minutes and then removed?
The balloon would be 13 cm.
Give the science definition of "acceleration".
The change in speed or direction of an object because an unbalanced force has acted upon it.
Sarah wanted to find out if temperature has an effect on the growth of bread mold. SHe grew mold in nine Petri dishes containing the same amount and type of nutrients. Three were kept at 0 C, three were kept at 90 C, and three were kept at 27 C. The containers were examined and the growth of the bread mold was recorded each Friday for five weeks. Which of the following would NOT be a suitable way to measure growth of bread mold, in this experiment?
The color of the bread mold spots.
Patrick and SpongeBob love to blow bubble! Patrick found some Super Bubble Soap at Sail-Mart. The ads claim that Super Bubble Soap will produce bubbles that are twice as big as bubble made with regular bubble soap. Patrick and SpongeBob made up two samples of bubble solution. One sample was made with 5oz. of Super Bubble Soap and 5oz. of water, while the other was made with the same amount of water and 5oz. of regular buble soap. Patrick and SpongeBob used their favorite bubble wands to blow 10 different bubbles and did their best to measure the diameter of each one. The results are shown in the chart. What should their conclusion be?
The data does not support the hypothesis, because "Super Bubbles" are not twice larger than "Regular Bubbles".
All of the following are examples that state a hypothesis:
The faster a river flows, the greater the erosion. The brighter the color of an orange, the juicier the fruit.
Draw two diagrams: "spring" and "elastic rubber band" - Label/ explain what would change the potential energy:
The further the band is pulled back the more potential energy there is. The less the band is pulled back the less potential energy there is. When band is pulled back: most potential energy. After band is released: least potential energy. When compressed or stretched, a spring gains elastic potential energy. The longer the spring and the more its pressed down, the greater the potential energy is.
What does amplitude measure?
The height of a wave compared with the resting point of the wave.
An experiment was conducted to determine how the strength of an electromagnet (a nail with wire coiled around it and connected to two sides of a battery) was related to the number of batteries connected to the electromagnet. The same magnet was connected to 1, 2, 3, 4, and 5 D cell batteries and each time was placed on top of a pile of 100 paper clips and lifted. What is the operational definition of "magnet strength" in this experiment?
The number of paper clips lifted.
Describe what happens when a wave passes through the ocean
The ocean wave energy travels horizontally, while individual water molecules move up and down, vertically.
Students in a science class did an experiment. In it they pointed a flashlight at a screen. They put the flashlight at different distances from the screen. Then they measured the size of the lighted spot. Which of the following would be a good operational definition of the "size of the lighted spot"?
The radius of the spot on the screen.
What do you predict will happen when a wave moves from a thinner substance, such as water, into a thicker substance, such as oil? Be sure to use the concepts of speed and refraction in your answer.
The speed of the wave depends on the medium through which it passes, so the speed will change when the wave passes from water into oil. I predict that the speed will decrease because it takes more force to move the heavier oil. The wave will probably also refract as it moves from one medium to the other.
Many scientists accept the theory that excess carbon dioxide emissions from cars and industry form a layer of gas in the upper atmosphere that traps heat. The result is an increase in the average temperature on Earth. Which observation supports this theory?
The summer of 2008 was one of the hottest seasons on Earth in recorded history.
What is the dependent variable in this experiment? Bill is writing an article about what laptops have the longest battery life. He gets three different computers and installs the same operating system on each. He runs a series of tests on the laptops and comes up with these results. Computer A lasts for 3.4 hours under regular conditions. Computer B lasts 2.6 hours under regular conditions. Computer C lasts 5.1 hours under regular conditions.
The time each computer battery lasts. Dependent variable what measures for result.
Students tested the effect of exercise on pulse rate. They measured their pulse rates at rest, after walking, and after climbing stairs. Which conclusion is logical based on the student's data?
The type of exercise has an effect on how much the pulse increases after activity.
A forest fire destroys trees in a large area. The forest rangers use the burned area to study the effect on different types of grasses on soil erosion. they choose ten plots of ground that are the same size. Each of these plots receives the same amount of sun. Each of these plots also has the same kind of soil and the same slope. The rangers plant each with a different type of grass. Measurements of soil erosion are made every week for the entire summer. What is the independent or manipulated variable in this study?
The types of grasses.
Describe the movement of a transverse wave.
The wave energy moves in a perpendicular direction to the up & down particle disturbance.
When waves pass around a solid barrier what do you predict will happen when the waves reach the barrier?
The waves will reflect off the barrier or diffract around the barrier
You want to determine if a new diet medication will make rats lose weight. What is the independent variable?
Then new diet medication
Draw two diagrams: "magnetic" and "static electric"- label and explain when they would have the greatest potential energy:
There is the most potential energy when the object is about to touch the magnet. There is the least potential energy when its farther away from the magnet. The closer they are together, the more potential energy there is.
What is constructive interference?
This is when the crests and troughs of two waves align exactly—they reinforce each other.
You want to determine if a new diet medication will help rats to lose weight. Why is it necessary to use two groups of rate in the experiment?
To compare rats taking the new medication to rats without the medication.
For what purpose should a scale be used?
To measure the mass of an object.
Why are multiple trials conducted during an experiment?
To reduce the effects of any inaccurate results.
A well designed experiment can only have one independent variable?
True
Sarah wanted to find out if temperature has an effect on the growth of bread mold. She grew mold in nine Petri dishes containing the same amount and type of nutrients. Three were kept at 0 C, three were kept at 90 C, and three were kept at 27 C. The containers were examined and the growth of the bread mold was recorded each Friday for five weeks. One of the controlled variables is:
Type of container used.
NASA rovers on Mars discover numerous smoothly rounded rocks containing iron that also show clear signs of oxidation (rusting). The rocks are discovered in a flat, open, completely dry valley, with no evidence of significant craters in the area. What inference may NASA scientists draw from this observation?
Water once flowed freely in this area of Mars.
What are you measuring when you measure from the crest of one wave to the next?
Wavelength
What are mechanical waves and what do they travel through?
Waves such as sound waves, seismic waves, ocean waves, crowd waves—they must have a medium (substance) to travel through, such as air, water, rock, etc.
explain how the outside force of gravity acts upon a basketball in an advantageous way, when a member of the "Atlanta Hawks" is trying to score a 3-point shot, or a free throw, for example?
When the basketball is thrown upward into the air, the force of gravity acts upon and makes the ball fall back downward toward the earth and thru the basket.
Longitudinal wave
this type of wave was made when we used the slinky and when we tapped the side of the aluminum pan. In this type of wave the direction of the disturbance and the direction of the wave are the same.
When a wave moves across a pond, it transfers water molecules (blank) and (blank) while (blank) moves across the pond.
up (first blank) down (second blank) energy (third blank)
Transverse wave
was made when we made a crowd wave, a wave with a rope, and one of the waves with the slinky. In a transverse wave the disturbance is in a perpendicular direction to the direction the wave (or energy) travels.
