How do strong and weak acids differ? Use lab tools on your computer to find out! Dip the paper or the probe into solution to measure the pH, or put in the electrodes to measure the conductivity. Then see how concentration and strength affect pH. Can a weak acid solution have the same pH as a strong acid solution?

Create your own shapes using colorful blocks and explore the relationship between perimeter and area. Compare the area and perimeter of two shapes side-by-side. Challenge yourself in the game screen to build shapes or find the area of funky figures. Try to collect lots of stars!

Build rectangles of various sizes and relate multiplication to area. Discover new strategies for multiplying algebraic expressions. Use the game screen to test your multiplication and factoring skills!

Build rectangles of various sizes and relate multiplication to area. Partition a rectangle into smaller areas and discover new strategies for multiplying decimals!

Build rectangles of various sizes and relate multiplication to area. Partition a rectangle into two areas to discover the distributive property.

Build rectangles of various sizes and relate multiplication to area. Discover new strategies for multiplying large numbers. Use the game screen to test your problem solving strategies!

Remember your multiplication tables? Practice your multiplication, division, and factoring skills with this exciting game. No calculators allowed!

Explore the interactions between various combinations of two atoms. Observe the total force acting on the atoms or the individual attractive and repulsive forces. Customize the attraction to see how changing the atomic diameter and interaction strength affects the interaction.

Play with objects on a teeter totter to learn about balance. Test what you've learned by trying the Balance Challenge game.

How do you know if a chemical equation is balanced? What can you change to balance an equation? Play a game to test your ideas!

Grab a balloon to explore concepts of static electricity such as charge transfer, attraction, repulsion, and induced charge.

“The thicker the glass, the darker the brew, the less the light that passes through.” Make colorful concentrated and dilute solutions and explore how much light they absorb and transmit using a virtual spectrophotometer!

Explore bending of light between two media with different indices of refraction. See how changing from air to water to glass changes the bending angle. Play with prisms of different shapes and make rainbows.

How does the blackbody spectrum of the sun compare to visible light? Learn about the blackbody spectrum of Sirius A, the sun, a light bulb, and the earth. Adjust the temperature to see the wavelength and intensity of the spectrum change. View the color of the peak of the spectral curve.

Build fractions from shapes and numbers to earn stars in this fractions game or explore in the Fractions Lab. Challenge yourself on any level you like. Try to collect lots of stars!

Starting from atoms, see how many molecules you can build. Collect your molecules and view them in 3D!

Build an atom out of protons, neutrons, and electrons, and see how the element, charge, and mass change. Then play a game to test your ideas!

Explore how a capacitor works! Change the size of the plates and the distance between them. Change the voltage and see charges build up on the plates. View the electric field, and measure the voltage. Connect a charged capacitor to a light bulb and observe a discharging RC circuit.

Arrange positive and negative charges in space and view the resulting electric field and electrostatic potential. Plot equipotential lines and discover their relationship to the electric field. Create models of dipoles, capacitors, and more!

Experiment with an electronics kit! Build circuits with batteries, resistors, ideal and non-Ohmic light bulbs, fuses, and switches. Determine if everyday objects are conductors or insulators, and take measurements with an ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a lifelike view.

Do you like Circuit Construction Kit: DC, but want to use only in-line ammeters? This is the sim for you! Experiment with an electronics kit. Build circuits with batteries, resistors, ideal and non-Ohmic light bulbs, fuses, and switches. Determine if everyday objects are conductors or insulators, and take measurements with a lifelike ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a lifelike view.

Investigate simple collisions in 1D and more complex collisions in 2D. Experiment with the number of balls, masses, and initial conditions. Vary the elasticity and see how the total momentum and kinetic energy change during collisions.

Make a whole rainbow by mixing red, green, and blue light. Change the wavelength of a monochromatic beam or filter white light. View the light as a solid beam, or see the individual photons.

Watch your solution change color as you mix chemicals with water. Then check molarity with the concentration meter. What are all the ways you can change the concentration of your solution? Switch solutes to compare different chemicals and find out how concentrated you can go before you hit saturation!

Visualize the electrostatic force that two charges exert on each other. Observe how changing the sign and magnitude of the charges and the distance between them affects the electrostatic force.

Drag data points and their error bars and watch the best-fit polynomial curve update instantly. You choose the type of fit: linear, quadratic, or cubic. The reduced chi-square statistic shows you when the fit is good. Or you can try to find the best fit by manually adjusting fit parameters.

Mix two gases to explore diffusion! Experiment with concentration, temperature, mass, and radius and determine how these factors affect the rate of diffusion.

Explore how heating and cooling iron, brick, water, and olive oil adds or removes energy. See how energy is transferred between objects. Build your own system, with energy sources, changers, and users. Track and visualize how energy flows and changes through your system.

Learn about the conservation of energy at the skate park! Build tracks, ramps, and jumps for the skater. View the skater's kinetic energy, potential energy, and thermal energy as they move along the track. Measure the speed and adjust the friction, gravity, and mass.

Learn about conservation of energy with a skater gal! Explore different tracks and view the kinetic energy, potential energy and friction as she moves. Build your own tracks, ramps, and jumps for the skater.

Explore what it means for a mathematical statement to be balanced or unbalanced by interacting with objects on a balance. Discover the rules for keeping it balanced. Collect stars by playing the game!

Explore what it means for a mathematical statement to be balanced or unbalanced by interacting with objects on a balance. Find all the ways to balance cats and dogs or apples and oranges.

Explore what it means for a mathematical statement to be balanced or unbalanced by interacting with integers and variables on a balance. Find multiple ways to balance x and y to build a system of equations.

Build coin expressions, then exchange them for variable expressions. Simplify and evaluate expressions until you are ready to test your understanding of equivalent expressions in the game!

Investigate Faraday's law and how a changing magnetic flux can produce a flow of electricity!

Explore the forces at work when pulling against a cart, and pushing a refrigerator, crate, or person. Create an applied force and see how it makes objects move. Change friction and see how it affects the motion of objects.

Match shapes and numbers to earn stars in this fractions game. Challenge yourself on any level you like. Try to collect lots of stars!

Build equivalent fractions with different denominators. Match shapes and numbers to earn stars in the game. Challenge yourself on any level you like. Try to collect lots of stars!

Explore fractions while you help yourself to 1/3 of a chocolate cake and wash it down with 1/2 a glass of water! Create your own fractions using fun interactive objects. Match shapes and numbers to earn stars in the fractions game. Challenge yourself on any level you like. Try to collect lots of stars!

Explore fractions while you help yourself to 1 and 1/2 chocolate cakes and wash it down with 1/3 a glass of water! Create your own fractions using fun interactive objects. Match shapes and numbers to earn stars in the mixed number game. Challenge yourself on any level you like. Try to collect lots of stars!

Move the Chemistry book and observe what happens.

Play with functions while you ponder Art History. Explore geometric transformations and transform your thinking about linear functions, then have fun figuring out the mystery functions!

Play with functions while you ponder Art History. Look for patterns, then apply what you learned on the Mystery screen!

Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other. Examine kinetic energy and speed histograms for light and heavy particles. Explore diffusion and determine how concentration, temperature, mass, and radius affect the rate of diffusion.

Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

Express yourself through your genes! See if you can generate and collect three types of protein, then move on to explore the factors that affect protein synthesis in a cell.

Explore the world of lines. Investigate the relationships between linear equations, slope, and graphs of lines. Challenge yourself in the line game!

Discover how changing coefficients changes the shape of a curve. View the graphs of individual terms (e.g. y=bx) to see how they add to generate the polynomial curve. Generate definitions for vertex, roots, and axis of symmetry. Compare different forms of a quadratic function. Define a curve by its focus and directrix.

Explore slope-intercept form of a line. Connect the slope and y-intercept to the equation of the line. Challenge yourself in the line game!

Visualize the gravitational force that two objects exert on each other. Adjust properties of the objects to see how changing the properties affects the gravitational attraction.

Visualize the gravitational force that two objects exert on each other. Discover the factors that affect gravitational attraction, and determine how adjusting these factors will change the gravitational force.

Move the sun, earth, moon and space station to see how it affects their gravitational forces and orbital paths. Visualize the sizes and distances between different heavenly bodies, and turn off gravity to see what would happen without it!

Stretch and compress springs to explore the relationships between force, spring constant, displacement, and potential energy! Investigate what happens when two springs are connected in series and parallel.

Are all atoms of an element the same? How can you tell one isotope from another? Use the sim to learn about isotopes and how abundance relates to the average atomic mass of an element.

Play with John’s foot and arm to explore when he gets a shock!

Create your own scatter plot or use real-world data and try to fit a line to it! Explore how individual data points affect the correlation coefficient and best-fit line.

Add numbers by making tens. Break apart and combine numbers while focusing on place value. Use the adding screen to add any two numbers. Use the game screen to apply your make-a-ten strategies!

Hang masses from springs and adjust the spring constant and damping. Transport the lab to different planets, or slow down time. Observe the forces and energy in the system in real-time, and measure the period using the stopwatch.

Hang masses from springs and discover how they stretch and oscillate. Compare two mass-spring systems, and experiment with spring constant. Transport the lab to different planets, slow down time, and observe the velocity and acceleration throughout the oscillation.

What determines the concentration of a solution? Learn about the relationships between moles, liters, and molarity by adjusting the amount of solute and solution volume. Change solutes to compare different chemical compounds in water.

When is a molecule polar? Change the electronegativity of atoms in a molecule to see how it affects polarity. See how the molecule behaves in an electric field. Change the bond angle to see how shape affects polarity.

Explore molecule shapes by building molecules in 3D! How does molecule shape change with different numbers of bonds and electron pairs? Find out by adding single, double or triple bonds and lone pairs to the central atom. Then, compare the model to real molecules!

Explore molecule shapes by building molecules in 3D! Find out how a molecule's shape changes as you add atoms to a molecule.

Turn light source on to explore. Observe what happens in the observation window as you set up different combinations of light source and molecule. Note this simulation is the first to support our pan and zoom feature, so zoom in for a closer look, if you need to.

Explore how organisms with different traits survive various selection agents within the environment.

Stimulate a neuron and monitor what happens. Pause, rewind, and move forward in time in order to observe the ions as they move across the neuron membrane.

What do elevation, account balances, and temperature have in common? They can all be represented on a number line. Compare integers on a number line and in an inequality statement. Discover the meaning of absolute value.

Explore operations with integers using an authentic context of net worth, then generalize with a number line. Experiment with adding and subtracting both positives and negatives, and make predictions about whether the total will be positive or negative.

See how the equation form of Ohm's law relates to a simple circuit. Adjust the voltage and resistance, and see the current change according to Ohm's law.

Play with one or two pendulums and discover how the period of a simple pendulum depends on the length of the string, the mass of the pendulum bob, the strength of gravity, and the amplitude of the swing. Observe the energy in the system in real-time, and vary the amount of friction. Measure the period using the stopwatch or period timer. Use the pendulum to find the value of g on Planet X. Notice the anharmonic behavior at large amplitude.

Drop balls through a triangular grid of pegs and see them accumulate in containers. Switch to a histogram view and compare the distribution of balls to an ideal binomial distribution. Adjust the binary probability and develop your knowledge of statistics!

Blast a car out of a cannon, and challenge yourself to hit a target! Learn about projectile motion by firing various objects. Set parameters such as angle, initial speed, and mass. Explore vector representations, and add air resistance to investigate the factors that influence drag.

Play with ratios and proportions by designing a necklace, throwing paint balloons, playing billiards, or shopping for apples! Make predictions about proportions before they are revealed.

Play with the left and right hands in different ways, and explore ratio and proportion. Start on the Discover screen to find each challenge ratio by moving the hands. Then, on the Create screen, set your own challenge ratios. Once you've found a challenge ratio, try to move both hands while maintaining the challenge ratio through proportional reasoning.

Create your own sandwich and then see how many sandwiches you can make with different amounts of ingredients. Do the same with chemical reactions. See how many products you can make with different amounts of reactants. Play a game to test your understanding of reactants, products and leftovers. Can you get a perfect score on each level?

Observe changes to the equation and wire as you play with the resistivity, length, and area sliders.

How did Rutherford figure out the structure of the atom without being able to see it? Simulate the famous experiment in which he disproved the Plum Pudding model of the atom by observing alpha particles bouncing off atoms and determining that they must have a small core.

Watch different types of molecules form a solid, liquid, or gas. Add or remove heat and watch the phase change. Change the temperature or volume of a container and see a pressure-temperature diagram respond in real time. Relate the interaction potential to the forces between molecules.

Heat, cool and compress atoms and molecules and watch as they change between solid, liquid and gas phases.

Take a tour of trigonometry using degrees or radians! Look for patterns in the values and on the graph when you change the value of theta. Compare the graphs of sine, cosine, and tangent.

Explore pressure under and above water. See how pressure changes as you change fluids, gravity, container shapes, and volume.

Discover the unit rate while shopping for fruits, vegetables, and candy. Construct a double number line and look for patterns. Challenge yourself on the race track as you compare cars with different rates!

Explore vectors in 1D or 2D, and discover how vectors add together. Specify vectors in Cartesian or polar coordinates, and see the magnitude, angle, and components of each vector. Experiment with vector equations and compare vector sums and differences.

Experiment with vector equations and compare vector sums and differences. Customize the base vectors or explore scalar multiplication by adjusting the coefficients in equation. Specify vectors in Cartesian or polar coordinates, and view the magnitude, angle, and components of each vector.

Make waves with a dripping faucet, audio speaker, or laser! Add a second source to create an interference pattern. Put up a barrier to explore single-slit diffraction and double-slit interference. Experiment with diffraction through elliptical, rectangular, or irregular apertures.

Explore the wonderful world of waves! Even observe a string vibrate in slow motion. Wiggle the end of the string and make waves, or adjust the frequency and amplitude of an oscillator.

Make waves with a dripping faucet, audio speaker, or laser! Adjust frequency and amplitude, and observe the effects. Hear the sound produced by the speaker, and discover what determines the color of light.

Test the pH of things like coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Visualize the relative number of hydroxide ions and hydronium ions in solution. Switch between logarithmic and linear scales. Investigate whether changing the volume or diluting with water affects the pH. Or you can design your own liquid!

Test the pH of everyday liquids such as coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Investigate how adding more of a liquid or diluting with water affects pH.

Subtraction is more than an operation- it is also the distance between two numbers! Explore the distance between a person and house, a bird and a fish, and the difference in temperature between two locations. Compare absolute distance and directed distance, and strengthen your number line muscles.