There are two types of catalysis reactions: homogeneous and heterogeneous. In a homogeneous reaction, the catalyst is in the same phase as the reactants. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. This activity addresses homogeneous catalysis.

Cellular respiration is the process by which our bodies convert glucose from food into energy in the form of ATP (adenosine triphosphate). Start by exploring the ATP molecule in 3D, then use molecular models to take a step-by-step tour of the chemical reactants and products in the complex biological processes of glycolysis, the Krebs cycle, the Electron Transport Chain, and ATP synthesis. Follow atoms as they rearrange and become parts of other molecules and witness the production of high-energy ATP molecules.

Explore what happens when a force is exerted on a ceramic material. There are many different types of materials. Each material has a particular molecular structure, which is responsible for the material's mechanical properties. The molecular structure of each material affects how it responds to an applied force at the macroscopic level.

Observe how a chemical reaction evolves over time and affects the balance of potential and kinetic energy in the system.

Explore the relationship between charge, electric fields, and forces on objects by manipulating charge.

Explore the role of charge in interatomic interactions. The forces attracting neutral atoms are called Van der Waals attractions, which can be weak or strong, depending on the atoms involved. Charged atoms (also known as ions) can repel or attract via Coulomb forces, and the forces involved are much stronger. Oppositely charged atoms attract to each other, while similarly charged atoms repel. The attractive forces between atoms have consequences for their interactions in physical, chemical and biological applications.

In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

Explore the energy exchange between colliding objects and observe how energy transfer occurs under various circumstances.

Investigate the difference in attractive force between polar and non-polar molecules by 'pulling' apart pairs of molecules. While all molecules are attracted to each other, some attractions are stronger than others. Non-polar molecules are attracted through a London dispersion attraction; polar molecules are attracted through both the London dispersion force and the stronger dipole-dipole attraction. The force of attractions between molecules has consequences for their interactions in physical, chemical and biological applications.

Investigate the difference in attractive force between polar and non-polar molecules by "pulling" apart pairs of molecules. While all molecules are attracted to each other, some attractions are stronger than others. Non-polar molecules are attracted through a London dispersion attraction; polar molecules are attracted through both the London dispersion force and the stronger dipole-dipole attraction. The force of attractions between molecules has consequences for their interactions in physical, chemical and biological applications.

Compare the change in potential energy when you separate molecules from each versus when you break molecules apart.

Explore a NetLogo model of populations of rabbits, grass, and weeds. First, adjust the model to start with a different rabbit population size. Then adjust model variables, such as how fast the plants or weeds grow, to get more grass than weeds. Change the amount of energy the grass or weeds provide to the rabbits and the food preference. Use line graphs to monitor the effects of changes you make to the model, and determine which settings affect the proportion of grass to weeds when rabbits eat both.

Before Ernest Rutherford's famous gold foil experiment in 1911, it was not known how the positive part of the atom was distributed. His experiment showed that if you shot positively charged particles at the atoms in a very thin sheet of gold foil, that very rarely, a particle would bounce back from the foil rather than going straight through it. Experiment with changing the distribution of positive charge and see how it affects the paths of positively charged particles moving near it.

This interactive, scaffolded activity allows students to build an atom within the framework of a newer orbital model. It opens with an explanation of why the Bohr model is incorrect and provides an analogy for understanding orbitals that is simple enough for grades 8-9. As the activity progresses, students build atoms and ions by adding or removing protons, electrons, and neutrons. As changes are made, the model displays the atomic number, net charge, and isotope symbol. Try the "Add an Electron" page to build electrons around a boron nucleus and see how electrons align from lower-to-higher energy. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology. The Concord Consortium develops deeply digital learning innovations for science, mathematics, and engineering. The models are all freely accessible. Users may register for additional free access to capture data and store student work products.

This interactive activity helps learners visualize the role of electrons in the formation of ionic and covalent chemical bonds. Students explore different types of chemical bonds by first viewing a single hydrogen atom in an electric field model. Next, students use sliders to change the electronegativity between two atoms -- a model to help them understand why some atoms are attracted. Finally, students experiment in making their own models: non-polar covalent, polar covalent, and ionic bonds. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology.

This 90-minute activity features six interactive molecular models to explore the relationships among voltage, current, and resistance. Students start at the atomic level to explore how voltage and resistance affect the flow of electrons. Next, they use a model to investigate how temperature can affect conductivity and resistivity. Finally, they explore how electricity can be converted to other forms of energy. The activity was developed for introductory physics courses, but the first half could be appropriate for physical science and Physics First. The formula for Ohm's Law is introduced, but calculations are not required. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology. The Concord Consortium develops deeply digital learning innovations for science, mathematics, and engineering.

This concept-building activity contains a set of sequenced simulations for investigating how atoms can be excited to give off radiation (photons). Students explore 3-dimensional models to learn about the nature of photons as "wave packets" of light, how photons are emitted, and the connection between an atom's electron configuration and how it absorbs light. Registered users are able to use free data capture tools to take snapshots, drag thumbnails, and submit responses. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology.

In this interactive activity, learners explore factors that cause atoms to form (or break) bonds with each other. The first simulation depicts a box containing 12 identical atoms. Using a slider to add heat, students can see the influence of temperature on formation of diatomic bonds. Simulations #2 and #3 introduce learners to reactions involving two types of atoms. Which atom forms a diatomic molecule more easily, and why? The activity concludes as students explore paired atoms (molecules). In this simulation they compare the amount of energy needed to break the molecular bonds to the energy needed to form the bonds. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology.

In this interactive activity, learners build computer models of atoms by adding or removing electrons, protons, and neutrons. It presents the orbital model of an atom: a nucleus consisting of protons and neutrons with electrons surrounding it in regions of high probability called orbitals. Guided tasks are provided, such as constructing a lithium atom and a carbon-12 atom in the fewest possible steps. The activity concludes with a model for building a charged hydrogen atom (an ion). Within each task, students take snapshots of their work product and answer probative questions. This item is part of the Concord Consortium, a nonprofit research and development organization dedicated to transforming education through technology.