Change the charge on spheres to positive or negative and observe how charges affect the interaction between them.

How does an object's speed change as it falls through the atmosphere? When first learning about how objects fall, usually just one force--gravity--is considered. Such a simplification only accurately describes falling motion in a vacuum. This model of a parachute carrying a load incorporates a second force--air resistance--and allows experimentation with two variables that affect its speed: the size of the parachute and the mass of its load. This model graphs both the parachute's height above the Earth's surface and its speed after it is released. Motion continues until a constant speed is achieved, the terminal velocity.

All the "stuff" that is around us, we call matter. Matter is made of either atoms or molecules much too small to see. We give these basic building blocks the general name of particles. Particles exist in three basic states: solids, liquids, and gases. Explore the characteristics of a gas from a molecular viewpoint.

All the "stuff' that is around us, we call matter. Matter is made of either atoms or molecules much too small to see. We give these basic building blocks the general name of particles. Particles exist in three basic states: solids, liquids, and gases. Explore the characteristics of a liquid from a molecular viewpoint.

All the "stuff" that is around us, we call matter. Matter is made of either atoms or molecules much too small to see. We give these basic building blocks of matter the general name of particles. Particles exist in three basic states: solids, liquids, and gases. Explore the characteristics of a solid from a molecular viewpoint.

Explore the factors that affect a pendulum's motion. A pendulum is a weight hung from a fixed point. Pendulums swing back and forth in a regular motion known as a period. The length of the period is affected by the pendulum itself. Experiment by changing the length of the string/rod, the mass of the weight, the angle at which the pendulum is released and the friction (or damping force) exerted on the pendulum. Which of these factors affect the period of the pendulum?

Explore the motion of a pendulum suspended by a spring. A pendulum is a weight hung from a fixed point. Pendulums swing back and forth in a regular motion known as a period. The period of a pendulum is affected by the length of the string/rod. A spring is a resilient device that can be pressed or pulled but return to its original shape when released. Springs are commonly helical coiled metal devices. When a spring is compressed or stretched and then released, it will vibrate at a particular frequency. This frequency is called the period of the spring. The period of a spring is affected by the spring constant (a measure of the elasticity of the coils). How does a pendulum behave when the length of the spring that suspends the mass is constantly changing?

In this activity, students explore phase change at a molecular level. They trace the path of an atom to view intermolecular interactions and investigate how temperature relates to phase change. Upon activity completion, students will be able to give examples of phase change, explain how the input of energy into a system affects the state of matter, and describe how both latent heat and evaporative cooling play a role in changes of phase.

Explore what happens at the molecular level during a phase change. The three common physical states of matter (also called phases) are solid, liquid and gas. Matter can change phase with the addition or subtraction of heat. Molecules are always in motion. The molecules in a solid move more slowly than those in a liquid. When molecules are heated, they gain kinetic energy (motion). Kinetic energy can be transferred through molecular collisions.

In this Investigation, students will work toward independent experimentation in the context of cellular respiration and photosynthesis through use of a series of physical labs and either CO2 sensors or a semi-quantitative leaf disk protocol. Students will explore changes in CO2 concentration in the context of spinach leaves in light and dark conditions then develop an independent experiment in groups or as a class to reason through timing of cellular respiration and photosynthesis. The scaffolding for experimentation is less than in previous Investigations, leaning on what students have already experienced in the lactase and osmosis experiments.

How do scientists detect planets around distant stars? Use this model to explore how a star's movement and light intensity are affected by an orbiting planet. Explore the effects of changing the orbiting angle (tilt), type, and size of the planet on the star's velocity and light intensity. Use the habitability analyzer to determine whether the planet could harbor life.

What do plants eat? This unit explores plants and how they make food.

Explore what happens when a force is exerted on a polymeric plastic 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.

The Plate Tectonics module "What will Earth look like in 500 million years?" helps students build a systems view of plate tectonics through focused case studies and interactions with the Seismic Explorer and Tectonic Explorer models. As students explore data about plate boundaries on Earth today, they make connections to what happened in Earth's past. Finally, they use their understanding of how Earth's plate system exists today to make predictions about what Earth may look like in 500 million years.

Observe how molecules with hydrophilic and hydrophobic regions move in a mixture of oil and water, and the effects on potential energy.

Explore the role of polarity in the strength of intermolecular attractions. 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.

Explore how the types of atoms forming a bond affect the distribution of electrons and overall shape of the molecule.

Many factors influence the success and survival rate of a population of living things. Explore several factors that can determine the survival of a population of sheep in this NetLogo model. Start with a model of unlimited grass available to the sheep and watch what happens to the sheep population! Next try to keep the population under control by removing sheep periodically. Change the birthrate, grass regrowth rate, and the amount of energy rabbits get from the grass to keep a stable population.

Explore how hydrophobic and hydrophilic interactions cause proteins to fold into specific shapes. Proteins, made up of amino acids, are used for many different purposes in the cell. The cell is an aqueous (water-filled) environment. Some amino acids have polar (hydrophilic) side chains while others have non-polar (hydrophobic) side chains. The hydrophilic amino acids interact more strongly with water (which is polar) than do the hydrophobic amino acids. The interactions of the amino acids within the aqueous environment result in a specific protein shape.

Generate all hydrophilic (polar), all hydrophobic (non-polar), or random proteins and observe how the protein folds in response to these molecular properties. Explore how the potential energy of the system changes over time to draw conclusions about how proteins develop stable structures.