Conservation of Matter

In this lesson, students discover how all science begins with a basic understanding of atoms, which are the building blocks of matter. Atoms are like puzzle pieces, joining with other atoms in chemical reactions to form bigger pieces of matter. As they combine or break apart, the total number and kind of atoms do not change. In this lesson, students conduct an experiment to compare the masses of two different substances, analyzing how matter is never created or destroyed.

• Matter is everything that has mass and takes up space. 
• An element is a substance made up entirely of one kind of atom. 
• An atom is the smallest piece of matter that has the properties of an element. 
• Matter has different properties—observable and measurable characteristics of matter. A substance’s properties depend on the number and kind of atoms that make it up. 
• Atoms combine with other atoms to form molecules. Different kinds of matter are made up of different kinds of atoms. 
• Matter is never created or destroyed. In a chemical reaction, the atoms are rearranged, but the total mass and number of protons, neutrons, and electrons never changes. 

• How can chemical properties be used to describe an atom?
• What would happen to the sun or moon if all of the atoms were removed?
• How does a closed system help scientists know if matter is created or destroyed in a chemical reaction?

Misconception: Earth does not move.

Fact: Earth is in constant motion. It is continually in motion, making one complete orbit around the sun in about one Earth year. At the same time, Earth rotates around its axis every 24 hours, causing day and night.

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

Cause and Effect : a relationship between events or things, where one is the result of the other

Chemical Reaction :  a change that rearranges the atoms of the original substances into a new substance that has different properties from the original substances

Conservation of Matter :  a theory that states atoms are not created or destroyed during a chemical reaction; they are rearranged to form new substances

Element :  a substance entirely made up of one kind of atom

Experiment :  a procedure designed to test whether a hypothesis is true, false, or inconclusive

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

Matter :  everything that has mass and takes up space

Physical Change :  a change that does not affect the chemical structure of a substance

Property :  an observable or measurable characteristic of matter

Science :  all knowledge gained from experiments

Matter in Space

From its position above Earth, the Hubble Space Telescope makes observations of Earth, the sun, and distant stars. Earth, the sun, and stars are examples of matter. Matter is everything that has mass and takes up space.

All matter is made up of tiny parts that are too small to be seen. These parts are called atoms. An atom is the smallest piece of matter that has the properties of an element. An element is a substance entirely made up of one kind of atom. There are 118 different kinds of elements. All matter is made up of combinations of the 118 elements.

Both nonliving things and living things are made up of atoms. Even though atoms make up both living and nonliving things, atoms are not alive.

Atoms are so tiny that we cannot see them. Just one grain of sand is made up of many millions of atoms. 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 much smaller than the atom itself. Because atoms are so tiny, scientists use scale to better understand the size of an atom, its smaller parts, and how it relates to everyday substances. Scale is the size, extent, or importance (magnitude) of something relative to something else.

For example, the protons and neutrons group together in the atom’s core, called the nucleus. If the atom is the size of a blueberry and you open 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.

Most of the atom is filled with empty space. The electrons are much smaller than the protons and the neutrons. They are in constant motion around the nucleus. However, there are huge amounts of space between each of the electrons and between the electrons and the nucleus.

Forming Matter

All of the matter that exists, including stars, planets, and all the other “stuff” in the universe, is made up of combinations of the 118 different kinds of elements. There are so many different kinds of matter because atoms are like Lego blocks. They can fit together with other atoms to form bigger pieces of matter.

Whenever two or more atoms join together, they create a molecule. Molecules are formed as a result of a chemical reaction between two or more atoms.

In a chemical reaction, the atoms of the original substances are rearranged to form new substances that have different properties from the original substances.

There are a couple of clues to look for to determine whether a chemical reaction has occurred. For example, a change in color or odor can be a sign that a chemical reaction has taken place. Also, if a gas forms when two different substances are mixed together, a chemical reaction has occurred. Rust is the result of a chemical reaction. It forms when the element iron combines with oxygen.

Conserving Matter

Chemical reactions occur when two or more atoms interact. The effect of this interaction is that the atoms are rearranged to form new molecules. However, the total number of atoms does not change in a chemical reaction. The mass of any one element at the beginning of a reaction will equal the mass of that same element at the end of the reaction.

This is called the conservation of matter. It states that atoms are never created or destroyed during a chemical reaction. They are rearranged to form new substances.

For scientists to measure that matter has been conserved, they must conduct the chemical reaction in a closed system. In a closed system, matter is prevented from being added or removed from the system. In contrast, in an open system, some of the mass is transferred to the environment, which is impossible to measure.

In this lesson, students create a closed system and carry out an experiment to see if matter is conserved during a chemical reaction. Students collect and analyze their own data before and after a reaction, looking for patterns that might indicate whether mass is conserved in a closed system after a chemical reaction.