Chapter 2: science, matter, energy, and systems Lesson 2.2: What is Matter?

What is matter? Learning objectives: Define matter and identify its building blocks Distinguish between physical and chemical changes Describe the law of conservation of matter

Matter consists of elements and compounds Matter is anything that has mass and takes up space. All matter exists in one of three physical states depending on temperature and pressure: Solid Liquid Gas Matter can be an element or a compound

elements An element is a type of matter with a unique set of properties that cannot be broken down into simpler substances by chemical means. Each element has a unique symbol. Elements are arranged in the Periodic Table of Elements according to their chemical behavior. There are currently 118 known elements on the Periodic Table of Elements

Rows are called periods Periodic Table of the Elements Created by Dmitri Mendeleev in 1869 Columns are called groups Each element has a symbol above its full name

compounds Most matter consists of compounds Compounds are combinations of two or more different elements held together in fixed proportions. Water is a compound consisting of two elements: Hydrogen (H) and Oxygen (O) Atoms are the basic building blocks of matter. An atom is the smallest unit of matter into which an element can be divided and still have its distinctive chemical properties.

The most widely accepted scientific theory in chemistry. Atomic theory All elements are made up of atoms Each atom has three different types of subatomic particles Neutrons – Have no charge and are found in the nucleus (center) of the atom Protons – Have a positive charge and are also found in the nucleus Electrons – Have a negative charge. They are much smaller than either protons or neutrons. They are constantly moving around the outside of the nucleus in an electron cloud. The most widely accepted scientific theory in chemistry. Neutron Proton Electron

Atomic motion Electrons don’t simply orbit the nucleus It is very difficult to predict where an electron is in the electron cloud.

Atomic numbers are unique. The number of protons determines the atomic number number of each element. Atomic numbers are unique. The Periodic Table of Elements is arranged by atomic number. Atomic number increases as you move from top left to bottom right.

Most atoms have the same number of protons and neutrons. Atomic mass The mass number of an atom is the total number of BOTH protons and neutrons in the nucleus. Electrons have very little mass compared to protons and neutrons so they don’t contribute to the atomic mass. Remember that the atomic number is equal to the number of protons in the nucleus. Most atoms have the same number of protons and neutrons. Carbon has an atomic number of 6 Therefore it has 6 protons It’s atomic mass is around 12, so it also has 6 neutrons.

Isotopes While an element always has the same number of protons, the number of neutrons can vary. A change in the number of neutrons also leads to a change in the mass number. The variation in neutrons and mass number leads to different forms of the same element called isotopes. The three most common isotopes are Carbon-12, Carbon-13, and Carbon-14

Molecules A molecule is another building block of matter. A molecule is a combination of two or more atoms of the same or different elements held together by chemical bonds. Water Ammonia Methane Carbon dioxide

ions Ions are another building block of matter. An ion is an atom or group of atoms with a charge (+ or -) The charge is written as a superscript. The net charge is a result of an atom having an unequal number of protons and electrons. The charge on an atom dictates how it will interact with other atoms.

Starch An organic compound is carbon- based. Molecules of life An organic compound is carbon- based. It contains at least 2 carbon atoms Examples are hydrocarbons and simple carbohydrates. Glucose contains Carbon, Hydrogen, and Oxygen. It is a simple sugar It is a carbohydrate It is the product of photosynthesis and it is how energy is stored in plants. Glucose molecules can be linked together to form starch. Starch

Hydrocarbons as fuel Isooctane

Hydrocarbons as fuel

Greenhouse gases in the atmosphere

The industrial revolution Historically, manufacturing of goods was done by hand in people’s homes. 1764: James Hargreaves invented the spinning jenny that allowed for one person to make many spools of thread at once. This invention was followed by improvements in the production of iron and steel. The invention of the steam engine revolutionized manufacturing and transportation. Factories spread throughout Europe and the United States.

Physical and chemical changes During a physical change there is no change in the chemical composition of matter. When ice melts or liquid water boils, water remains H2O During a chemical change or chemical reaction there is a change in the chemical composition of the substances involved. When coal is burned, solid Carbon combines with Oxygen in the atmosphere and forms Carbon dioxide (CO2) Carbon + Oxygen = Carbon dioxide + Energy C + O2 = CO2

Law of conservation of matter Elements and compounds can change from one physical or chemical form to another, but atoms cannot be created or destroyed. Atoms, ions, or molecules can only rearrange into different spatial patterns (physical changes) or chemical combinations (chemical changes). Law of conservation of matter Atoms cannot be created or destroyed

Atoms cannot be created or destroyed Law of conservation Antoine-Laurent Lavoisier and his wife Marie-Ann performed multiple experiments demonstrating that matter/mass is conserved. These experiments utilized accurate balances and were often performed in sealed glass containers. Why are these two things important? Atoms cannot be created or destroyed