Thermal Energy and Particle Motion

Students use the phenomenon of boiling water to explore the relationship between matter and energy, carrying out an experiment to observe how water molecules change their motion when thermal energy transfers into or out of the water.

• Matter makes up all of the “stuff” around us and it is made up of smaller particles called atoms.
• Matter is different from energy, but the two are connected. All matter has energy, and matter cannot change without energy.
• Energy can transfer into or out of systems or objects.
  
  

• What are some different examples of matter?
• What would happen to the ice cream or water (or other matter being discussed) if all of the atoms were removed?
• If all matter is made up of atoms, why isn’t all matter exactly the same?
• Why is air matter, even though we can’t see it?
• What happens to the thermal energy in food that you cook once you remove the pan from the heat?
  
  

Misconception: Conservation of mass does not apply to atoms.

Fact: Mass is the measure of the amount of atoms in a substance, so conservation of mass refers to atoms, which cannot be created or destroyed.

Misconception: The atoms of the reactants in a chemical reaction are transformed into other atoms.

Fact: The atoms aren’t changed into other atoms. Instead, the atoms stay the same but rearrange to form new molecules. 

Atom : the smallest piece of matter that has the properties of an element; a combination of three subatomic particles: protons, neutrons, and electrons

Conduction : heat transfer that occurs when molecules collide

Energy : the ability to do work

Kinetic energy : the energy of motion

Mass : a measure of the amount of matter that makes up an object or substance; measured in grams (g)

Matter : everything that has mass and takes up space

Molecule : a combination of two or more atoms bonded together

Potential energy : energy that is stored

Property : an observable or measurable characteristic of a substance

Scale : the size, extent, or importance (magnitude) of something relative to something else

Structure : the way in which parts are put together to form a whole

System : a set of connected, interacting parts that form a more complex whole

Temperature : a measure of heat; measured in Celsius with a thermometer

Thermal energy : the motion of atoms and molecules in a substance or object as its temperature increases

Food is Matter

Today Mario Batali is a famous chef. But he remembers watching his Italian grandmother making her own pasta every Sunday. She would put her homemade ravioli or gnocchi into boiling water to cook it. He says that watching her do this played a major role in his becoming a chef.

Pasta is a kind of matter. Matter is anything that has mass and takes up space. Mass is a measure of the amount of matter that makes up an object or substance. It is measured in grams (g).

Properties of Matter

The mass of an object is one property of that object. A property is an observable or measurable characteristic of a substance. Physical properties include color, texture, mass, volume, and density. Volume is a measure of how much space an object or substance takes up. It is measured in cubic meters (m3) for solids with a ruler, or liters (L) or milliliters (mL) for liquids.

Density is the amount of mass in a unit volume of a substance. Different elements have different densities. Density is a useful physical property for identifying an unknown substance because the amount or sample size of a material does not affect its density. Because most substances change volume when they are heated or cooled, densities are temperature dependent.

Each kind of matter has the properties it does because of the atoms that make it up. An atom is the smallest piece of matter that has the properties of an element. An element is a substance made up entirely of one kind of atom. All matter is made up of a specific combination of atoms.

To understand why matter has the properties it does, scientists begin with the structure of atoms that make it up. Structure is the way in which parts are put together to form a whole.

Atoms are so tiny that we cannot see them without special instruments. Because of this, scientists use scale to understand how the size of atoms relates to everyday objects. Scale is the size, extent, or importance (magnitude) of something relative to something else.

Scale of an Atom

For example, think about a grapefruit. If each atom in the grapefruit were the size of a blueberry, the grapefruit would have to be the size of Earth. There are so many atoms in just one grapefruit that they are impossible to count. Imagine having to fill up the entire planet with blueberries. That’s about how many atoms are in one grapefruit.

Atoms themselves are made up of smaller particles called protons, neutrons, and electrons. These smaller particles are called subatomic particles. These subatomic particles are much smaller than the atom itself. The protons and neutrons group together in the atom’s core, called the nucleus. If the atom were the size of a blueberry and you opened the blueberry up, the nucleus would be too small to see.

If you were to make the blueberry the size of a football field, you would just be able to see the nucleus. It would be the size of a small marble. The nucleus holds all of the atom’s protons and neutrons. The electrons are smaller than the protons or neutrons. They are in constant motion around the nucleus. However, most of the atom is filled with empty space. There are vast regions of space between each of the electrons and between the electrons and the nucleus.

How Matter Forms

Atoms are like Lego blocks, fitting together with other atoms to form bigger pieces of matter. Whenever two or more atoms bond (join together), they form molecules. Each kind of matter has the properties it does because of the number and kind of atoms and molecules that make it up. Molecules can be small, made up of one or two atoms. Or they can be made up of thousands of atoms.

For example, oxygen (O2) is a molecule made up of two oxygen atoms bonded together. It is a gas at room temperature. It is colorless and odorless. Hydrogen (H2) is a molecule made up of two hydrogen atoms bonded together. Like oxygen, it is also a gas at room temperature. It is also colorless and odorless. It has the lowest density of all the elements.

Water (H2O) is a molecule that forms when two hydrogen atoms and one oxygen atom bond. It is a liquid at room temperature. It is odorless and almost colorless, except for a hint of blue.
 
The Relationship Between Matter and Energy

Matter cannot change without energy. This is why you need a pot of boiling water to cook pasta. Energy is the ability to do work. Work is any change in position, speed, or state of matter due to force (a push or pull that acts on an object, changing its speed, direction, or shape). Examples of work include heating an object or moving an object. Energy can either be stored or in motion. Energy that is stored is called potential energy. The energy of motion is called kinetic energy.

For the hands-on activity in this lesson, students develop an experiment to explore how the motion of water molecules in a closed system changes when thermal energy is added to or removed from the system. Students collect and analyze data on the height of the water when it is exposed to different temperatures of water, looking for patterns that might indicate a relationship between the amount of thermal energy added or removed and the motion of the water molecules.