Structure of Matter 8th Grade Science

Vocabulary Terms Atom Electron Law of Conservation of Matter Matter Neutron Nucleus Proton

Neither is CORRECT! Is this glass half empty or half full? What is matter? Is this glass half empty or half full? Neither is CORRECT!

What is Matter? The glass is FULL! Half of the glass is full of water The other half is full of air What is air? Air is a mixture of several gases Mostly made up of Nitrogen and Oxygen

What is Matter? Nitrogen and Oxygen are kinds of matter. Matter is anything that has mass and takes up space. You cannot hold or see air, but it is still matter. We know air is not there when we cannot breathe.

Matter Water is also matter Most of the things you can see, taste, smell, and touch are made of matter. Name other things that are matter:

What is NOT matter? You could not see what was going on around you without light. Light has no mass and does not take up space. So light is NOT matter. Is heat matter? Heat also has no mass and does not take up space. So heat is not matter. Your thoughts, feelings, and ideas are not matter

What makes up matter? I take wood from a tree and run it through a saw. Is it still wood? I take the sawed piece of wood and put it into a chipper. Are the chips still wood? I take the wood chips and grind them into saw dust. Is the saw dust still wood?

Matter How far can I break down saw dust before it is no longer smaller versions of wood? All matter eventually breaks down to their atomic structure. No atom can be broken down into something smaller.

In your Science Notebook…Answer the following: List 3 things that are NOT matter. List 3 things that are matter. Time: 5 Minutes Use Your Noodle Time!

Ideas of matter. Greek philosopher – Democritus (460 B.C. to 370 B.C.) Thought the universe was made of empty space and tiny bits of stuff called atoms. Atom comes from the Greek word that means “cannot be divided”. Believed atoms couldn’t be broken down into smaller pieces. Definition of atom: An atom is the basic unit of an element. An atom is a form of matter which may not be further broken down using any chemical means. A typical atom consists of protons, neutrons and electrons.

Democritus’s Ideas About Atoms All matter is made of atoms. There are empty spaces between atoms Atoms are complete solids Atoms do not have anything inside them Atoms are different in size, shape and weight.

Democritus’s Ideas About Atoms Thought that different types of atoms existed for every type of matter. Thought the different atoms explained the different characteristics of each type of matter. Gold Silver Iron

Summarize: What is an atom? Time: 5 Minutes In your Science Notebook…Answer the following: Summarize: What is an atom? Time: 5 Minutes Use Your Noodle Time!

Can matter be made or destroyed? People thought matter disappeared when it burned or rusted. Seeing objects grow, like trees, also made people think that matter could be made.

Lavoisier French Chemist Lived about 2,000 years after Democritus Lavoisier studied wood fires. He showed that the wood and oxygen it combines with during the fire have the same mass as the ash, gases, and water vapor that are produced by the fire. Matter is not destroyed when wood burns. It just changes into a different form.

Law of Conservation of Matter Lavoisier’s work created this law This law states that matter is not created or destroyed – matter only changes form. Example Total mass of Total mass of Wood + Oxygen = Ash + Gases + Water Vapor

In your Science Notebook…Answer the following: Apply: Suppose you increase the mass of wood you are burning in a fireplace. What will happen to the total mass of ash, gases and water vapor? Time: 3 Minutes Use Your Noodle Time!

Models of the Atom Models often are used for things that are too small or too large to be observed. Models also are used for things that are difficult to understand.

Dalton’s Model John Dalton was an English chemist during the 1800’s. His atomic model was a set of ideas instead of an object. Believed matter was made of atoms that were too small to see.

Dalton’s Atomic Theory of Matter He thought that each type of matter was made of only one kind of atom. Example: Gold bars are made of gold atoms Iron rods are made of iron atoms The different type of atoms explains why gold and iron are different. Scientists studied Dalton’s model and it became known as the Atomic Theory of Matter.

In your Science Notebook…Answer the following: Explain: Dalton’s atomic model was not an object. What was it? Time: 3 Minutes Use Your Noodle Time!

How small is an atom? Atoms are so small that it would take about 1 million of them lined up in a row to be about as thick as one human hair.

What is an electron? An English scientist named J.J. Thomson discovered the electron in the early 1900s. He experimented using a glass tube with a metal plate at each end.

Thomson Cathode Ray Thomson connected the metal plates to electricity. One plate called the anode, had a positive charge. The other plate, called the cathode, had a negative charge.

Thomson’s Cathode Ray During his experiments, Thomson watched rays travel from the cathode to the anode. Then he used a magnet to bend the rays.

Thomson’s Cathode Ray Since the rays could be bent, they were made of particles that had mass and charge. He knew that like charges repel and opposite charges attract. Since the rays were traveling to the positive plate, Thomson decided the rays must be made of particles with a negative charge.

Thomson’s Cathode Ray These invisible particles with negative charges are electrons. Thomson showed that atoms can be divided into smaller particles.

Explain: Why was Thomson’s discovery important? Time: 3 Minutes In your Science Notebook…Answer the following: Explain: Why was Thomson’s discovery important? Time: 3 Minutes Use Your Noodle Time!

What was Thomson’s model of the atom? Matter that has an equal amount of positive and negative charge is neutral Most matter is neutral So, Thomson thought an atom was made of a ball of positive charge with negatively charged electrons in it.

Thomson’s model His model of an atom was like a ball of chocolate chip cookie dough. The dough was positively charged. The chocolate chips were the negatively charged electrons.

Explain: What did Thomson think an atom was made of? Time: 3 Minutes In your Science Notebook…Answer the following: Explain: What did Thomson think an atom was made of? Time: 3 Minutes Use Your Noodle Time!

What was Rutherford’s model of the atom? Scientists still had questions about how the atom was arranged and about particles with positive charge. Around 1910, English scientist named Earnest Rutherford and his team tried to answer these questions.

Rutherford’s Experiment Rutherford’s team shot tiny, high-energy, positively charged particles (aka Alpha Particles) at a very thin piece of gold foil. They thought the alpha particles would pass easily through the foil Most did pass straight through But, other alpha particles changed direction. A few of them even bounced back.

Gold Foil Experiment

Rutherford’s Experiment Since most particles passed straight through the gold, he thought that the gold atoms must be made of mostly empty space. But, because a few particles bounced off something, the gold atoms must have some positively charged object within the empty space.

Rutherford’s Experiment He called this positively charged object the nucleus. The nucleus is the positively charged, central part of an atom. Rutherford named the positively charged particles in the nucleus of the atom protons. He also suggested that negatively charged electrons were scattered in the empty space around the nucleus.

Bonus Points!! You have ONE Minute!! There are 3 parts of an atom… Rutherford was able to explain the Protons and Electrons. Do you know what part of the atom Rutherford did not find? You have ONE Minute!!

How was the neutron discovered? Rutherford was puzzled by one observation in his experiment with alpha particles. The nucleus of an atom seemed to be heavier after the experiment. He did not know where this extra mass came from.

Neutron James Chadwick, one of Rutherford’s students, answered the question: the nuclei were not getting heavier. But, the atoms had given off new particles. He found that the path of the new particles was not affected an electric field. This meant that new particles were neutral – had no charge.

Neutron Chadwick called these new particles neutrons. A neutron is a neutral particle in the nucleus of an atom This proton-neutron model of the nucleus of an atom is still accepted today.

Question your Science Notebook…Answer the following: Explain: Question #1: In Rutherford’s model, what is an atom mostly made of? Question #2 What type of charge do neutrons have? Time: 5 Minutes Use Your Noodle Time!

Improving the Atomic Model A scientist named Niels Bohr found that electrons are arranged in energy levels in an atom. He found that there is a maximum number of electrons that can be held in layers around the atom. Example 1st layer can hold no more than 2 electrons 2nd layer can hold no more than 8 electrons 3rd layer can hold no more than 18 electrons

What is the modern atomic model? Today, scientists realize that electrons have characteristics similar to both waves and particles. So, electrons do not orbit the nucleus of an atom in paths. Instead, electrons move in a cloud around the nucleus.

Electron Cloud

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Question your Science Notebook…Answer the following: Compare and Contrast: How is Bohr’s atomic model different from the modern atomic model? Time: 5 Minutes Use Your Noodle Time!

You have 6 Minutes! Review! Explain the law of conservation of matter. Answer the following in your Science Notebook. Explain the law of conservation of matter. How could you explain the modern atomic model to another student? You have 6 Minutes!

Fill in each blank in the concept map. Matter is made of that have a Nucleus and that has