Teacher Presets let you save the Gizmo configuration and load it at any time

3D Eclipse Observe the motions of the Earth, Moon and Sun in three dimensions to investigate the causes and frequency of eclipses. Observe Earth's shadow crossing the Moon during a lunar eclipse, and the path of the Moon's shadow across Earth's surface during a solar eclipse. The angle of the Moon's orbit can be adjusted, as well as the distance of the Moon from the Earth.

Adding Whole Numbers and Decimals (Base-10 Blocks) Use base-10 blocks to model two numbers. Then combine the blocks to model the sum. Blocks of equal value can be exchanged from one area of the mat to the other to help understand carrying when adding. Four sets of blocks are available to model different place values.

Advanced Circuits Build compound circuits with series and parallel elements. Calculate voltages, resistance, and current across each component using Ohm's law and the equivalent resistance equation. Check your answers using a voltmeter, ammeter, and ohmmeter. Learn the function of fuses as a safety device.

Atwood Machine Measure the height and velocity of two objects connected by a massless rope over a pulley. Observe the forces acting on each mass throughout the simulation. Calculate the acceleration of the objects, and relate these calculations to Newton's Laws of Motion. The mass of each object can be manipulated, as well as the mass and radius of the pulley.

Balancing Blocks (Volume) This Gizmo provides you with two challenges. First, use blocks to build a figure with a given volume. Then, try to balance the blocks on a platform that sits on the tip of a cone. The dimensions of the platform can be adjusted, and blocks can be added or deleted by clicking on the model.

Bohr Model: Introduction Fire photons to determine the spectrum of a gas. Observe how an absorbed photon changes the orbit of an electron and how a photon is emitted from an excited electron. Calculate the energies of absorbed and emitted photons based on energy level diagrams. The light energy produced by the laser can be modulated, and a lamp can be used to view the entire absorption spectrum at once.

Boyle's Law and Charles' Law Investigate the properties of an ideal gas by performing experiments in which the temperature is held constant (Boyle's Law), and others in which the pressure remains fixed (Charles' Law). The pressure is controlled through the placement of masses on the lid of the container, and temperature is controlled with an adjustable heat source.

Building Pangaea In 1915, Alfred Wegener proposed that all of Earth's continents were once joined in an ancient supercontinent he called Pangaea. Wegener's idea of moving continents led to the modern theory of plate tectonics. Create your own version of Pangaea by fitting Earth's landmasses together like puzzle pieces. Use evidence from fossils, rocks, and glaciers to refine your map.

Calorimetry Lab Investigate how calorimetry can be used to find relative specific heat values when different substances are mixed with water. Modify initial mass and temperature values to see effects on the system. One or any combination of the substances can be mixed with water. A dynamic graph (temperature vs. time) shows temperatures of the individual substances after mixing.

Cannonball Clowns (Number Line Estimation) Launch clowns from a circus cannon and try to hit the target. Drag digit cards on the control panel to set the launch distance and choose an appropriate unit of distance. After practicing your clown-launching skills on a number line, move on to the Big Top, Football Field, School Buses, the Golden Gate Bridge, and more!

Cat and Mouse (Modeling with Linear Systems) Experiment with a system of two lines representing a cat-and-mouse chase. Adjust the speeds of the cat and mouse and the head start of the mouse, and immediately see the effects on the graph and on the chase. Connect real-world meaning to slope, y-intercept, and the intersection of lines.

Cell Division Begin with a single cell and watch as mitosis and cell division occurs. The cells will go through the steps of interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. The length of the cell cycle can be controlled, and data related to the number of cells present and their current phase can be recorded.

Chemical Equations Practice balancing chemical equations by changing the coefficients of reactants and products. As the equation is manipulated, the amount of each element is shown as individual atoms, histograms, or numerically. Molar masses of reactants and products can also be calculated and balanced to demonstrate conservation of mass.

Chicken Genetics Breed "pure" chickens with known genotypes that exhibit specific feather colors, and learn how traits are passed on via codominant genes. Chickens can be stored in cages for future breeding, and the statistics of feather color are reported every time the chickens breed. Punnett squares can be used to predict results.

Chocomatic (Multiplication, Arrays, and Area) Use the Chocomatic to design candy bars made out of chocolate squares. Use multiplication to find the number of squares in each chocolate bar. Build collections of chocolate bars that all have the same number of squares. Solve multiplication problems by joining two smaller chocolate bars into a large bar.

Colligative Properties Determine how the physical properties of a solvent are dependent on the number of solute particles present. Measure the vapor pressure, boiling point, freezing point, and osmotic pressure of pure water and a variety of solutions. Compare the effects of four solutes (sucrose, sodium chloride, calcium chloride, and potassium chloride) on these physical properties.

Conduction and Convection Two flasks hold colored water, one yellow and the other blue. Set the starting temperature of each flask, choose a type of material to connect the flasks, and see how quickly the flasks heat up or cool down. The flasks can be connected with a hollow pipe, allowing the water in the flasks to mix, or a solid chunk that transfers heat but prevents mixing.

Density Measure the mass and volume of a variety of objects, then place them into a beaker of liquid to see if they float or sink. Learn to predict whether objects will float or sink in water based on their mass and volume. Compare how objects float or sink in a variety of liquids, including gasoline, oil, seawater, and corn syrup.

Density Experiment: Slice and Dice Drop a chunk of material in a beaker of water and observe whether it sinks or floats. Cut the chunk into smaller pieces of any size, and observe what happens as they are dropped in the beaker. The mass and volume of each chunk can be measured to gain a clear understanding of density and buoyancy.

Density Laboratory With a scale to measure mass, a graduated cylinder to measure volume, and a large beaker of liquid to observe flotation, the relationship between mass, volume, density, and flotation can be investigated. The density of the liquid in the beaker can be adjusted, and a variety of objects can be studied during the investigation.

Diffusion Explore the motion of particles as they bounce around from one side of a room to the other through an adjustable gap or partition. The mass of the particles can be adjusted, as well as the temperature of the room and the initial number of particles. In a real-world context, this can be used to learn about how odors travel, fluids move through gaps, the thermodynamics of gases, and statistical probability.

Distance-Time and Velocity-Time Graphs Create a graph of a runner's position versus time and watch the runner run a 40-yard dash based on the graph you made. Notice the connection between the slope of the line and the velocity of the runner. Add a second runner (a second graph) and connect real-world meaning to the intersection of two graphs. Also experiment with a graph of velocity versus time for the runners, and also distance traveled versus time.

Distance-Time and Velocity-Time Graphs Create a graph of a runner's position versus time and watch the runner run a 40-meter dash based on the graph you made. Notice the connection between the slope of the line and the velocity of the runner. Add a second runner (a second graph) and connect real-world meaning to the intersection of two graphs. Also experiment with a graph of velocity versus time for the runners, and also distance traveled versus time.

Distance-Time Graphs Create a graph of a runner's position versus time and watch the runner complete a 40-meter dash based on the graph you made. Notice the connection between the slope of the line and the speed of the runner. What will the runner do if the slope of the line is zero? What if the slope is negative? Add a second runner (a second graph) and connect real-world meaning to the intersection of two graphs.

Distance-Time Graphs Create a graph of a runner's position versus time and watch the runner complete a 40-yard dash based on the graph you made. Notice the connection between the slope of the line and the speed of the runner. What will the runner do if the slope of the line is zero? What if the slope is negative? Add a second runner (a second graph) and connect real-world meaning to the intersection of two graphs.

Doppler Shift Observe sound waves emitted from a moving vehicle. Measure the frequency of sound waves in front of and behind the vehicle as it moves, illustrating the Doppler effect. The frequency of sound waves, speed of the source, and the speed of sound can all be manipulated. Motion of the vehicle can be linear, oscillating, or circular.

Doppler Shift Advanced Derive an equation to calculate the frequency of an oncoming sound source and a receding sound source. Also, calculate the Doppler shift that results from a moving observer and a stationary sound source. The source velocity, sound velocity, observer velocity, and sound frequency can all be manipulated.

Drug Dosage A drug prescription must be carefully planned to maximize benefit while avoiding an overdose. In this Gizmo, you can give a patient one or more pills and monitor the levels of medication in the body through time. Based on the reaction of the patient, determine the ideal levels of medication. Create a dosage schedule so these levels are maintained through time. Four types of pills, each with a different release pattern and target organ, are available for use.

Dye Elimination When a foreign substance such as a drug is ingested, it often remains in the bloodstream for a long time. This Gizmo models the elimination of substances from the bloodstream using water and dye. Add dye to a container of water, and then add beakers of pure water while removing beakers of dyed water. The amount of dye remaining is recorded after each cycle. The volumes of all containers can be adjusted, as well as the amount of dye used. This provides a good example of exponential decay.

Earthquakes 1 - Recording Station Using an earthquake recording station, learn how to determine the distance between the station and an earthquake based on the time difference between the arrival of the primary and secondary seismic waves. Use this data to find the epicenter in the Earthquakes 2 - Location of Epicenter Gizmo.

Earthquakes 2 - Determination of Epicenter Locate the epicenter of an earthquake by analyzing seismic data from three recording stations. Measure difference in P- and S-wave arrival times, then use data from the Earthquakes 1 - Recording Station Gizmo to find the distance of the epicenter from each station.

Effect of Environment on New Life Form Using the scientific method, control the environmental conditions for a fictional alien organism in order to learn how the organism responds to changes in conditions. Sunlight, water, and temperature can be varied to determine their effects on the shape of the aliens.

Electromagnetic Induction Explore how a changing magnetic field can induce an electric current. A magnet can be moved up or down at a constant velocity below a loop of wire, or the loop of wire may be dragged in any direction or rotated. The magnetic and electric fields can be displayed, as well as the magnetic flux and the current in the wire.

Element Builder Use protons, neutrons, and electrons to build elements. As the number of protons, neutrons, and electrons changes, information such as the name and symbol of the element, the Z, N, and A numbers, the electron dot diagram, and the group and period from the periodic table are shown. Each element is classified as a metal, metalloid, or nonmetal, and its state at room temperature is also given.

Energy Conversion in a System A falling cylinder is attached to a rotating propeller that stirs and heats the water in a beaker. The mass and height of the cylinder, as well as the quantity and initial temperature of water can be adjusted. The temperature of the water is measured as energy is converted from one form to another.

Energy of a Pendulum Perform experiments with a pendulum to gain an understanding of energy conservation in simple harmonic motion. The mass, length, and gravitational acceleration of the pendulum can be adjusted, as well as the initial angle. The potential energy, kinetic energy, and total energy of the oscillating pendulum can be displayed on a table, bar chart or graph.

Equilibrium and Concentration Observe how reactants and products interact in reversible reactions. The initial amount of each substance can be manipulated, as well as the pressure on the chamber. The amounts, concentrations, and partial pressures of each reactant and product can be tracked over time as the reaction proceeds toward equilibrium.

Equivalent Fractions (Fraction Tiles) Explore fractions using the Fractionator, the machine that makes fraction tiles. Compare fractions and find equivalent fractions by arranging the tiles on two horizontal rows. Explore simplifying fractions. Add fractions and express sums as improper fractions or mixed numbers.

Evolution: Natural and Artificial Selection Observe evolution in a fictional population of bugs. Set the background to any color, and see natural selection taking place. Compare the processes of natural and artificial selection. Manipulate the mutation rate, and determine how mutation rate affects adaptation and evolution.

Factor Trees (Factoring Numbers) The Factor Trees Gizmo has two modes. In Factor mode, you can create factor trees to factor composite numbers into primes. In Build mode, you can build numbers by multiplying primes together. Can you build all composite numbers up to 50? Any whole composite number up to 999 can be factored or built with the Gizmo.

Fan Cart Physics Gain an understanding of Newton's Laws by experimenting with a cart (on which up to three fans are placed) on a linear track. The cart has a mass, as does each fan. The fans exert a constant force when switched on, and the direction of the fans can be altered as the position, velocity, and acceleration of the cart are measured.

Flower Pollination Observe the steps of pollination and fertilization in flowering plants. Help with many parts of the process by dragging pollen grains to the stigma, dragging sperm to the ovules, and removing petals as the fruit begins to grow. Quiz yourself when you are done by dragging vocabulary words to the correct plant structure.

Force and Fan Carts Explore the laws of motion using a simple fan cart. Use the buttons to select the speed of the fan and the surface, and press Play to begin. You can drag up to three objects onto the fan cart. The speed of the cart is displayed with a speedometer and recorded in a table and a graph.

Forest Ecosystem Observe and manipulate the populations of four creatures (trees, deer, bears, and mushrooms) in a forest. Investigate the feeding relationships (food web) in the forest. Determine which creatures are producers, consumers, and decomposers. Pictographs and line graphs show changes in populations over time.

Fraction Artist 2 (Area Models of Fractions) Extend understanding of fractions by making modern paintings in the style of Piet Mondrian. Create and analyze paintings with different-sized sections. Compare the sizes of unit fractions. Find creative ways to color one-half of a painting. This can be a nice introduction to adding fractions with unlike denominators.

Fraction Garden (Comparing Fractions) Plant flowers in two gardens to help develop fraction sense. The two gardens act as number lines, from 0 to 1. Use the flowers in the gardens to compare fractions and to explore equivalent fractions. Chalk marks can be drawn to divide the garden into equal sections.

Fraction, Decimal, Percent (Area and Grid Models) Model and compare fractions, decimals, and percents using area models. Each area model can have 10 or 100 sections and can be set to display a fraction, decimal, or percent. Click inside the area models to shade them. Compare the numbers visually or on a number line.

Fractions Greater than One (Fraction Tiles) Explore fractions greater than one with the Fractionator, a fraction-tile-making machine in the Gizmo. Create sums of fraction tiles on two number lines. Sums greater than one are shown as improper fractions on the top number line, and as mixed numbers on the bottom number line.

Free Fall Tower Recreate Galileo's famous experiment by dropping objects off the Tower of Pisa. You can drop ping pong balls, golf balls, soccer balls or watermelons. Objects can be dropped in air or no air, with or without a parachute. The speed of each object is shown on a speedometer and a graph.

Free-Fall Laboratory Investigate the motion of an object as it falls to the ground. A variety of objects can be compared, and their motion can be observed in a vacuum, in normal air, and in denser air. The position, velocity, and acceleration are measured over time, and the forces on the object can be displayed. Using the manual settings, the mass, radius, height, and initial velocity of the object can be adjusted, as can the air density and wind.

Function Machines 1 (Functions and Tables) Drop a number into a function machine, and see what number comes out! You can use one of the six pre-set function machines, or program your own function rule into one of the blank machines. Stack up to three function machines together. Input and output can be recorded in a table and on a graph.

Function Machines 2 (Functions, Tables, and Graphs) Drop a number into a function machine, and see what number comes out! You can use one of the six pre-set function machines, or program your own function rule into one of the blank machines. Stack up to three function machines together. Input and output can be recorded in a table and on a graph.

Function Machines 3 (Functions and Problem Solving) Drop a number into a function machine, and see what number comes out! You can use one of the six pre-set function machines, or program your own function rule into one of the blank machines. Stack up to three function machines together. Input and output can be recorded in a table and on a graph.

Golf Range Try to get a hole in one by adjusting the velocity and launch angle of a golf ball. Explore the physics of projectile motion in a frictional or ideal setting. Horizontal and vertical velocity vectors can be displayed, as well as the path of the ball. The height of the golfer and the force of gravity are also adjustable.

Graphing Skills Create a graph (bar graph, line graph, pie chart, or scatter plot) based on a given data set. Title the graph, label the axes, and choose a scale. Adjust the graph to fit the data, and then check your accuracy. The Gizmo can also be used to create a data table based on a given graph.

Gravity Pitch Imagine a gigantic pitcher standing on Earth, ready to hurl a huge baseball. What will happen as the ball is thrown harder and harder? Find out with the Gravity Pitch Gizmo. Observe the path of the ball when it is thrown at different velocities. Throw the ball on different planets to see how each planet's gravity affects the ball.

Greenhouse Effect Within this simulated region of land, daytime's rising temperature and the falling temperature at night can be measured, along with heat flow in and out of the system. The level of greenhouse gases present in the atmosphere at any given time can be adjusted, allowing the long-term effects to be investigated.

Greenhouse Effect Within this simulated region of land, daytime's rising temperature and the falling temperature at night can be measured, along with heat flow in and out of the system. The amount of greenhouse gases present in the atmosphere can be adjusted through time, and the long-term effects can be investigated.

Growing Plants Investigate the growth of three common garden plants: tomatoes, beans, and turnips. You can change the amount of light each plant gets, the amount of water added each day, and the type of soil the seed is planted in. Observe the effect of each variable on plant height, plant mass, leaf color and leaf size. Determine what conditions produce the tallest and healthiest plants. Height and mass data are displayed on tables and graphs.

Half-life Investigate the decay of a radioactive substance. The half-life and the number of radioactive atoms can be adjusted, and theoretical or random decay can be observed. Data can be interpreted visually using a dynamic graph, a bar chart, and a table. Determine the half-lives of two sample isotopes as well as samples with randomly generated half-lives.

Hardy-Weinberg Equilibrium Set the initial percentages of three types of parrots in a population and track changes in genotype and allele frequency through several generations. Analyze population data to develop an understanding of the Hardy-Weinberg equilibrium. Determine how initial allele percentages will affect the equilibrium state of the population.

Hearing: Frequency and Volume Test your hearing range by listening to low-, medium-, and high-frequency sounds. Compare the relative loudness of sounds at each frequency to create an equal-loudness curve. In a quiet room, measure your threshold of audibility for each frequency, and compare your results to others. The volume of each sound can be adjusted.

Herschel Experiment Shine sunlight through a prism and use a thermometer to measure the temperature in different regions of the spectrum. The thermometer can be dragged through the visible spectrum and beyond. This recreates the experiment of William Herschel that led to the discovery of infrared radiation in 1800.

Holiday Snowflake Designer Fold paper and cut in a certain way to make symmetrical snowflakes with six sides (similar to what can be found in nature) or with eight sides (an easier folding method). This simulation allows you to cut virtual paper on the computer screen with round dot or square dot "scissors" of various sizes before using physical paper.

Homeostasis Control a simulated person running on a treadmill. Your challenge is to use clothing, exercise, and sweat to maintain a constant body temperature as air temperature goes up and down. Sweating (perspiration) can be controlled automatically by the Gizmo or, for a challenge, manually by the user. Don't forget to eat and drink!

Household Energy Usage Explore the energy used by many household appliances, such as television sets, hair dryers, lights, computers, etc. Make estimates for how long each item is used on a daily basis to get an estimate for the total power consumed during a day, a week, a month, and a year, and how that relates to consumer costs and environmental impact.

Human Evolution - Skull Analysis Compare the skulls of a variety of significant human ancestors, or hominids. Use available tools to measure lengths, areas, and angles of important features. Each skull can be viewed from the front, side, or from below. Additional information regarding the age, location, and discoverer of each skull can be displayed.

Human Homeostasis Adjust the levels of clothing, perspiration, and exercise to maintain a stable internal temperature as the external temperature changes. Water and blood sugar levels need to be replenished regularly, and fatigue occurs with heavy exercise. Severe hypothermia, heat stroke, or dehydration can result if internal stability is not maintained.

Inclined Plane - Rolling Objects Observe and compare objects of different shapes as they roll or slide down an inclined plane. Compare the percentages of translational and rotational kinetic energy for each object, and see how this affects how quickly each object moves. The slope of each ramp can be adjusted, and a variety of materials can be used for the objects and ramps.

Inclined Plane - Sliding Objects Investigate the energy and motion of a block sliding down an inclined plane, with or without friction. The ramp angle can be varied and a variety of materials for the block and ramp can be used. Potential and kinetic energy are reported as the block slides down the ramp. Two experiments can be run simultaneously to compare results as factors are varied.

Independent and Dependent Events Compare the theoretical and experimental probabilities of drawing colored marbles from a bag. Record results of successive draws to find the experimental probability. Perform the drawings with replacement of the marbles to study independent events, or without replacement to explore dependent events.

Ionic Bonds Simulate ionic bonds between a variety of metals and nonmetals. Select a metal and a nonmetal atom, and transfer electrons from one to the other. Observe the effect of gaining and losing electrons on charge, and rearrange the atoms to represent the molecular structure. Additional metal and nonmetal atoms can be added to the screen, and the resulting chemical formula can be displayed.

Laser Reflection Point a laser at a mirror and compare the angle of the incoming beam to the angle of reflection. A protractor can be used to measure the angles of incidence and reflection, and the angle of the mirror can be adjusted. A beam splitter can be used to split the beam. Both plane and irregular mirrors can be used.

Longitudinal Waves Observe the propagation of longitudinal (compression) waves in a closed or open tube with evenly-spaced dividers. The strength and frequency of the waves can be manipulated, or waves can be observed as individual pulses. Compare the movement of dividers to graphs of displacement, velocity, acceleration and pressure.

Magnetism Drag bar magnets and a variety of other objects onto a piece of paper. Click Play to release the objects to see if they are attracted together, repelled apart, or unaffected. You can also sprinkle iron filings over the magnets and other objects to view the magnetic field lines that are produced.

Mascot Election (Pictographs and Bar Graphs) A brand new school is opening and it is time to elect the school mascot! Students can choose the Eagle, Lion, Bear, or Wolf. Voting results can be displayed in a table, tally chart, pictograph, bar graph, circle graph, or dot plot. You can change student votes by selecting a group of students and clicking a mascot.

Melting Points Every substance has unique transition points, or temperatures at which one phase (solid, liquid, or gas) transitions to another. Use a realistic melting point apparatus to measure the melting points, boiling points, and/or sublimation points of different substances and observe what these phase changes look like at the microscopic level. Based on the transition points, make inferences about the relative strengths of the forces holding these substances together.

Microevolution Observe the effect of predators on a population of parrots with three possible genotypes. The initial percentages and fitness levels of each genotype can be set. Determine how initial fitness levels affect genotype and allele frequencies through several generations. Compare scenarios in which a dominant allele is deleterious, a recessive allele is deleterious, and the heterozygous individual is fittest.

Modeling Fractions (Area Models) Model and compare fractions using area models. Set the denominators with the arrow buttons, and then set the numerators with the arrow buttons or by clicking in the models. Compare fractions visually, on a number line, or numerically using the least common denominator.

Modeling Whole Numbers and Decimals (Base-10 Blocks) Model numbers with base-10 blocks. Drag flats, rods, and individual cubes onto a mat to model a number. Blocks can be exchanged from one area of the mat to the other. Four sets of blocks are available to model a variety of whole numbers and decimals.

Mouse Genetics (One Trait) Breed "pure" mice with known genotypes that exhibit specific fur colors, and learn how traits are passed on via dominant and recessive genes. Mice can be stored in cages for future breeding, and the statistics of fur color are reported every time a pair of mice breed. Punnett squares can be used to predict results.

Mouse Genetics (Two Traits) Breed "pure" mice with known genotypes that exhibit specific fur and eye colors, and learn how traits are passed on via dominant and recessive genes. Mice can be stored in cages for future breeding, and the statistics of fur and eye color are reported every time a pair of mice breed. Punnett squares can be used to predict results.

Multiplying Decimals (Area Model) Model the product of two decimals by finding the area of a rectangle. Estimate the area of the rectangle first. Then break the rectangle into several pieces and find the area of each piece (partial product). Add these areas together to find the whole area (product).

Mystery Powder Analysis Perform multiple experiments using several common powders such as corn starch, baking powder, baking soda, salt, and gelatin. The results of the research on the known powders can then be used to analyze several unknowns using the scientific method. The unknowns can be a single powder or a combination of the known powders.

Number Line Frog Hop (Addition and Subtraction) Live a frog's life as you hop along a number line in search of flies. Learn how addition and subtraction can be represented as movement along a number line. Fred the frog may even help you get better at adding and subtracting two-digit numbers in your head by decomposing them into tens and ones.

Ocean Mapping Use a sonar on a boat to remotely measure the depth of an ocean at various locations. Describe multiple points on the ocean floor using their latitude, longitude, and depth. View maps of ocean depth in two and three dimensions, and use these maps to plot a safe route for ships to follow.

Orbital Motion - Kepler's Laws Learn Kepler's three laws of planetary motion by examining the orbit of a planet around a star. The initial position, velocity, and mass of the planet can be varied as well as the mass of the star. The foci and centers of orbits can be displayed and compared to the location of the star. The area swept out by the planet in a given time period can be measured, and data on orbital radii and periods can be plotted in several ways.

Paramecium Homeostasis Observe how a paramecium maintains stable internal conditions in a changing aquatic environment. Water moves into the organism by osmosis, and is pumped out by the contractile vacuole. The concentration of solutes in the water will determine the rate of contractions in the paramecium.

Penumbra Effect Observe the partial shadows cast by a rectangular block lit by multiple light sources. The number of light sources ranges from one to five, and individual lights can be turned on or off. The light spacing, block width, and distance from the lights to the block can be varied. Light intensity can be observed on a detector.

Permutations and Combinations Experiment with permutations and combinations of a number of letters represented by letter tiles selected at random from a box. Count the permutations and combinations using a dynamic tree diagram, a dynamic list of permutations, and a dynamic computation by the counting principle.

Phase Changes Explore the relationship between molecular motion, temperature, and phase changes. Compare the molecular structure of solids, liquids, and gases. Graph temperature changes as ice is melted and water is boiled. Find the effect of altitude on phase changes. The starting temperature, ice volume, altitude, and rate of heating or cooling can be adjusted.

Phased Array Observe the wave fronts produced by four closely-spaced emitters. The spacing and phase shift of each wave source can be adjusted, as well as the wave velocity. With all four sources you can observe a region of constructive interference that moves over time. The phased array has several real world applications such as radar and ultrasound.

Phases of the Moon Understand the phases of the Moon by observing the positions of the Moon, Earth and Sun. A view of the Moon from Earth is shown on the right as the Moon orbits Earth. Learn the names of Moon phases and in what order they occur. Click Play to watch the Moon go around, or click Pause and drag the Moon yourself.

Photoelectric Effect Shoot a beam of light at a metal plate in a virtual lab and observe the effect on surface electrons. The type of metal as well as the wavelength and intensity of the light can be adjusted. An electric field can be created to resist the electrons and measure their initial energies.

Photosynthesis Lab Study photosynthesis in a variety of conditions. Oxygen production is used to measure the rate of photosynthesis. Light intensity, carbon dioxide levels, temperature, and wavelength of light can all be varied. Determine which conditions are ideal for photosynthesis, and understand how limiting factors affect oxygen production.

Pith Ball Lab Pith balls with positive, negative, or no electrical charge are suspended from strings. The charge and mass of the pith balls can be adjusted, along with the length of the string, which will cause the pith balls to change position. Distances can be measured as variables are adjusted, and the forces (Coulomb and gravitational) acting on the balls can be displayed.

Polling: City Poll residents in a large city to determine their response to a yes-or-no question. Estimate the actual percentage of yes votes in the whole city. Examine the results of many polls to help assess how reliable the results from a single poll are. See how the normal curve approximates a binomial distribution for large enough polls.

Polling: Neighborhood Conduct a phone poll of citizens in a small neighborhood to determine their response to a yes-or-no question. Use the results to estimate the sentiment of the entire population. Investigate how the error of this estimate becomes smaller as more people are polled. Compare random versus non-random sampling.

Prisms and Cylinders Vary the height and base-edge or radius length of a prism or cylinder and examine how its three-dimensional representation changes. Determine the area of the base and the volume of the solid. Compare the volume of an oblique prism or cylinder to the volume of a right prism or cylinder.

Pulley Lab Use a pulley system to lift a heavy weight to a certain height. Measure the force required to lift the weight using up to three fixed and three movable pulleys. The weight to be lifted and the efficiency of the pulley system can be adjusted, and the height of the weight and the total input distance are reported.

Reaction Time 1 (Graphs and Statistics) Test your reaction time by catching a falling ruler or clicking a target. Create a data set of experiment results, and calculate the range, mode, median, and mean of your data. Data can be displayed on a list, table, bar graph or dot plot. The Reaction Time 1 Student Exploration focuses on range, mode, and median.

Reaction Time 2 (Graphs and Statistics) Test your reaction time by catching a falling ruler or clicking a target. Create a data set of experiment results, and calculate the range, mode, median, and mean of your data. Data can be displayed on a list, table, bar graph or dot plot. The Reaction Time 2 Student Exploration focuses on mean.

Reading Topographic Maps Understand how topographic maps work by creating a three-dimensional landscape and observing the corresponding contour lines. See how mountains, depressions, valleys and cliffs are represented on topographic maps. Fill in the landscape with water to demonstrate that contours are lines of constant elevation.

Real-Time Histogram Try to click your mouse once every 2 seconds. The time interval between each click is recorded, as well as the error and percent error. Data can be displayed in a table, histogram, or scatter plot. Observe and measure the characteristics of the resulting distribution when large amounts of data are collected.

Refraction Determine the angle of refraction for a light beam moving from one medium to another. The angle of incidence and each index of refraction can be varied. Using the tools provided, the angle of refraction can be measured, and the wavelength and frequency of the waves in each substance can be compared as well.

Reverse the Field Measure the time required to write a word when the mouse behaves in a normal fashion and when the direction of motion is reversed from left to right, up to down, or both. Run several experiments in each mode to see if your brain and muscles are able to adapt to the new direction of motion. Determine which type of inversion is easiest to adjust to and whether you can train yourself to function normally when the inversion is present.

Ripple Tank Study wave motion, diffraction, interference, and refraction in a simulated ripple tank. A wide variety of scenarios can be chosen, including barriers with one or two gaps, multiple wave sources, reflecting barriers, or submerged rocks. The wavelength and strength of waves can be adjusted, as well as the amount of damping in the tank.

RNA and Protein Synthesis Go through the process of synthesizing proteins through RNA transcription and translation. Learn about the many steps involved in protein synthesis including: unzipping of DNA, formation of mRNA, attaching of mRNA to the ribosome, and linking of amino acids to form a protein.

Roller Coaster Physics Adjust the hills on a toy-car roller coaster and watch what happens as the car careens toward an egg (that can be broken) at the end of the track. The heights of three hills can be manipulated, along with the mass of the car and the friction of the track. A graph of various variables of motion can be viewed as the car travels, including position, speed, acceleration, potential energy, kinetic energy, and total energy.

Seasons Around the World Use a three dimensional view of the Earth, Moon and Sun to explore seasonal changes at a variety of locations. Strengthen your knowledge of global climate patterns by comparing solar energy input at the Poles to the Equator. Manipulate Earth's axis to increase or diminish seasonal changes.

Seasons in 3D Gain an understanding of the causes of seasons by observing Earth as it orbits the Sun in three dimensions. Observe the path of the Sun across the sky on any date and from any location. Create graphs of solar intensity and day length, and use collected data to describe and explain seasonal changes.

Seasons: Earth, Moon, and Sun Observe the motions of the Earth, Moon and Sun in three dimensions to explain Sunrise and Sunset, and to see how we define a day, a month, and a year. Compare times of Sunrise and Sunset for different dates and locations. Relate shadows to the position of the Sun in the sky, and relate shadows to compass directions.

Seasons: Why do we have them? Learn why the temperature in the summertime is higher than it is in the winter by studying the amount of light striking the Earth. Experiment with a plate detector to measure the amount of light striking the plate as the angle of the plate is adjusted (and then use a group of plates placed at different locations on the Earth) and measure the incoming radiation on each plate.

Seed Germination Perform experiments with several seed types to see what conditions yield the highest germination (sprouting) rate. Three different types of seeds can be studied, and the temperature, water and light in the germination chamber can be controlled. No two trials will have the same result so repeated trials are recommended.

Shoot the Monkey Fire a banana cannon at a monkey in a tree. The monkey drops from the tree at the moment the banana is fired from the cannon. Determine where to aim the cannon so the monkey catches the banana. The position of the cannon, launch angle and initial velocity of the banana can be varied. Students can observe the velocity vectors and the paths of the monkey and banana.

Sight vs. Sound Reactions Measure your reaction time by clicking your mouse as quickly as possible when visual or auditory stimuli are presented. The individual response times are recorded, as well as the mean and standard deviation for each test. A histogram of data shows overall trends in sight and sound response times. The type of test as well as the symbols and sounds used are chosen by the user.

Simple Harmonic Motion Observe two different forms of simple harmonic motion: a pendulum and a spring supporting a mass. Use a stopwatch to measure the period of each device as you adjust the mass hanging from the spring, the spring constant, the mass of the pendulum, the length of the pendulum, and the gravitational acceleration.

Solubility and Temperature Add varying amounts of a chemical to a beaker of water to create a solution, observe that the chemical dissolves in the water at first, and then measure the concentration of the solution at the saturation point. Either potassium nitrate or sodium chloride can be added to the water, and the temperature of the water can be adjusted.

Solving Linear Systems (Matrices and Special Solutions) Explore systems of linear equations, and how many solutions a system can have. Express systems in matrix form. See how the determinant of the coefficient matrix reveals how many solutions a system of equations has. Also, use a draggable green point to see what it means for an (*x*, *y*) point to be a solution of an equation, or of a system of equations.

Solving Linear Systems (Standard Form) Solve systems of linear equations, written in standard form. Explore what it means to solve systems algebraically (with substitution or elimination) and graphically. Also, use a draggable green point to see what it means when (*x*, *y*) values are solutions of an equation, or of a system of equations.

Sound Beats and Sine Waves Listen to and see interference patterns produced by sound waves with similar frequencies. Test your ability to distinguish and match sounds as musicians do when they tune their instruments. Calculate the number of "sound beats" you will hear based on the frequency of each sound. [Note: Headphones are recommended for this Gizmo.]

Subtractive Colors Move spots of yellow, cyan, and magenta pigment on a white surface. As the colors overlap, other colors can be seen due to color subtraction. The color of most things you see--such as cars, leaves, paintings, houses, and clothes--are due to color subtraction. The intensity of the cyan, magenta, and yellow can be adjusted, and the RGB value at any location can be measured.

Target Sum Card Game (Multi-digit Addition) Play an addition card game! The goal is to create a sum that is as close as possible to the target sum. Students will deepen their understanding of place value as they get better at playing the game. Many game options allow students to vary the game for more practice. The game can be played with one or two players.

Temperature and Particle Motion Observe the movement of particles of an ideal gas at a variety of temperatures. A histogram showing the Maxwell-Boltzmann velocity distribution is shown, and the most probable velocity, mean velocity, and root mean square velocity can be calculated. Molecules of different gases can be compared.

Theoretical and Experimental Probability Experiment with spinners and compare the experimental probability of a particular outcome to the theoretical probability. Select the number of spinners, the number of sections on a spinner, and a favorable outcome of a spin. Then tally the number of favorable outcomes.

Time Estimation Try to estimate the passage of time by selecting a time interval, clicking the Start button, and clicking Stop when you think the interval has passed. The estimate and percent error are recorded. Compare different techniques for estimating time, as well as the average error for long time intervals versus shorter intervals.

Torque and Moment of Inertia One of the simplest machines is a see-saw lever. Place up to eight objects on the lever at different locations and try to balance it. Calculate net torque and moment of inertia based on the positions of the objects and the mass of the bar. The mass of each object can be changed, and the fulcrum position can be shifted as well.

Treasure Hunter (Decimals on the Number Line) Drive a desert highway searching for buried treasure. Learn to use the car's tens, ones, tenths, and hundredths gears, along with a GPS system (number line), to find the right place to dig. Plot your find on a zoomable number line map. Can you become a master Treasure Hunter?

Water Pollution Get to know the four main types of pollution present in the environment, and then look at a variety of real-world examples as you try to guess what type of pollution is represented by each situation. All of the real-world situations can be viewed every day in different parts of the world.

Weather Maps Learn about standard symbols used in meteorology to construct weather maps. Rain, sleet, snow, temperature, cloud cover, wind speed and direction, and atmospheric pressure can all be recorded at two different weather stations on a map. Describe weather patterns characteristic of high-pressure systems, low-pressure systems, warm fronts, and cold fronts.