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Unit 3 Lesson 2 Atoms and Molecules Vocabulary

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Atoms combine to form many different substances

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Atoms combine to form many different substances

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An Atom is a part of an element | An element is a specific type of atom

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An Atom is a part of an element | An element is a specific type of atom

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Carbon dioxide is a compound that consists of two atoms of oxygen and an atom of carbon. Pure substances don't have to be mixed and cannot be broken down without complex processes. Because carbon dioxide is natural and can't be broken down easily, it's a pure substance.
The Air We Breathe
We take in oxygen from the air when we breathe, and we also release carbon dioxide. The air we breathe is made up of several substances. We tend to think of oxygen as being the main component of air because our bodies need it to live, but oxygen is just a small part of the makeup of air. Actually, 78 percent of the air that we breathe is nitrogen, while another 21 percent is oxygen.

Other gases make up what's left of the chemical composition of air. Argon, methane, helium, krypton, hydrogen, xenon, and iodine are present in small amounts. You can find small amounts of compounds in air as well. Carbon dioxide is in the air we breathe, along with ozone, nitrogen dioxide, and a trace amount of carbon monoxide. There are also small amounts of water vapor in the air we breathe.
T he Exchange of Oxygen and Carbon Dioxide
When we breathe, we're getting the oxygen we need from the air to survive. The cells in our body use oxygen to create energy. As we take air into our lungs, millions of tiny sacs called alveoli take the oxygen in. The walls of the alveoli are thin enough to release the oxygen into our bloodstream, and our blood carries oxygen throughout our body.
H ow Plants and Trees Help Us Breathe
The energy that our bodies expend creates carbon dioxide, so the breathing process works in reverse to remove the carbon dioxide from our bodies. Our blood carries carbon dioxide back to the lungs, where we release it as we exhale.
C arbon Dioxide and Pollution
Plants and trees help us with the exchange between carbon dioxide and oxygen during the day by doing the reverse of what humans do. Plants don't exactly breathe like we do because they don't have lungs, but what they do is a process called photosynthesis and respiration.
O ther Forms of Carbon Dioxide
At night, plants take in oxygen and release carbon dioxide just like we do. During the day, plants use the light of the sun to take in carbon dioxide to create nutrients. They release oxygen back into the atmosphere. This process is why plants are so important for human survival because they produce so much of the oxygen we need to survive.

Even though carbon dioxide occurs naturally and is an important part of the life of plants, there's a definite relationship between carbon dioxide and pollution. Much of the pollution in our atmosphere occurs because of too much carbon dioxide that factories and fossil fuel burning transportation creates.

Proponents of climate change believe that eliminating carbon dioxide from the atmosphere will prevent warming of the planet. Environmentalists believe that changing the fuels we use will help cut down on the carbon dioxide that we release into the atmosphere.

Carbon dioxide is a gas, and we can't see or taste it when we breathe air. But we can witness carbon dioxide in other forms. The fizz in soft drinks, sparkling wine, and some types of beer comes from carbon dioxide. The bubbles and fizz are the effects of the carbon dioxide as it's released back into the air, and it's why we refer to these type of drinks as carbonated beverages.

If you've seen dry ice, you've witnessed another form of carbon dioxide. Dry ice is frozen carbon dioxide, and it's so cold that the air that hits it condenses and creates fog, which is why we see it used to create fog and haze for plays and concerts. At the coldest temperature of all time in Antarctica in 1983, carbon dioxide turned into snow, and space scientists have made a note of carbon dioxide snow on Mars as well.

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Carbon dioxide is a compound that consists of two atoms of oxygen and an atom of carbon. Pure substances don't have to be mixed and cannot be broken down without complex processes. Because carbon dioxide is natural and can't be broken down easily, it's a pure substance.

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Pure Substances

A pure substance is any single type of material that are made of only one type of atom or only one type of molecule. Also, a pure substance can be defined as any single type of material that has not been contaminated by another substance. In chemistry, a pure substance has a definite composition. It can be a compound or a single element. An element is a pure substance that cannot be separated into simpler substances by chemical or physical means. There are about 117 elements, but carbon, hydrogen, nitrogen and oxygen are only a few that make up the largest portion of Earth. The material is no longer a pure substance if it has been mixed with another pure substance. Two pure substances mixed together are known as a mixture. Scientists often use filtration to separate pure substances from a mixture in order to analyze the materials.

A chemical substance can be solid, liquid, gas, or plasma. Pure substances are often called pure to set them apart from mixtures. A substance can be anything. It doesn't have to consist of a single element or type of molecule. Pure hydrogen is a pure substance. So is pure honey, even though it consists of many different types of molecules. What makes both of these materials pure substances is that they are free from contamination. If you add some oxygen to the hydrogen, the resulting gas is neither pure hydrogen nor pure oxygen. If you add corn syrup to the honey, you no longer have pure honey. Pure alcohol could be ethanol, methanol or a mixture of different alcohols, but as soon as you add water, which is not alcohol, you no longer have a pure substance.

Most of the pure substances that you encounter in your daily life have been made pure by people through refining.

Examples of Pure Substances:

It has the same composition no matter where it comes from. Gold is made up of gold atoms. There are no other elements or compounds added to gold.

They are formed deep within Earth in only a very few areas. All the particles in a diamond are the same.

Considered a pure substance if the water contains only hydrogen and oxygen. Pure water is difficult to find in nature. Even the clearest spring water contains dissolved minerals. In nature, pure substances tend to mix with other substances

4. Baking soda

Although there are a multitude of uses for baking soda, in its simplest form, it is not contaminated with any other chemical compounds.

5. Table salt

One of the most common household chemicals. Table salt is 97% to 99% sodium chloride. Pure sodium chloride is an ionic crystal solid.

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Pure Substances A pure substance is any single type of material that are made of only one type of atom or only one type of molecule. Also, a pure substance can be defined as any single type of material that has not been contaminated by another substance.

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Kid’s learn about the science of the molecules. Tiny chemistry and compounds of atoms and elements make up all matter.

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How to read the periodic table of elements

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How to read the periodic table of elements

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Science >> Chemistry for Kids

The Periodic Table is a way of listing theelements. Elements are listed in the table by the structure of their atoms. This includes how many protons they have as well as how many electrons they have in their outer shell. From left to right and top to bottom, the elements are listed in the order of their atomic number, which is the number of protons in each atom.

Periodic Table of Elements
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Why is it called the Periodic Table?

It is called "periodic" because elements are lined up in cycles or periods. From left to right elements are lined up in rows based on their atomic number (the number of protons in their nucleus). Some columns are skipped in order for elements with the same number of valence electrons to line up on the same columns. When they are lined up this way, elements in the columns have similar properties.

Each horizontal row in the table is a period. There are seven (or eight) total periods. The first one is short and only has two elements, hydrogen and helium. The sixth period has 32 elements. In each period the left most element has 1 electron in its outer shell and the right most element has a full shell.

Groups

Groups are the columns of the periodic table. There are 18 columns or groups and different groups have different properties.

One example of a group is the noble or inert gases. These elements all line up in the eighteenth or last column of the periodic table. They all have a full outer shell of electrons, making them very stable (they tend not to react with other elements). Another example is the alkali metals which all align on the left-most column. They are all very similar in that they have only 1 electron in their outer shell and are very reactive. You can see all the groups in the table below.

This lining-up and grouping of similar elements helps chemists when working with elements. They can understand and predict how an element might react or behave in a certain situation.

Element Abbreviations

Each element has its own name and abbreviation in the periodic table. Some of the abbreviations are easy to remember, like H for hydrogen. Some are a bit harder like Fe for iron or Au for gold. For gold the "Au" comes from the Latin word for gold "aurum".

Who invented it?

The periodic table was proposed by Russian chemist Dmitri Mendeleev in 1869. Using the table, Mendeleev was able to accurately predict the properties of many elements before they were actually discovered.

Fun facts about the Periodic Table

Carbon is unique in that it is known to form up to 10 million different compounds. Carbon is important to the existence of life.

Francium is the rarest element on earth. There are probably no more than a few ounces of it on earth at any given time.

The only letter not in the periodic table is the letter J.

The country Argentina is named after the element silver (symbol Ag) which is argentum in Latin.

Although there is helium on Earth, it was first discovered by observing the sun.

Activities

Take a ten question quiz on this page.

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Full Periodic Table

Periodic Table with detailed information
(click for larger view)

More on the elements and the Periodic Table

Elements

More Chemistry Subjects

Science >> Chemistry for Kids

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Science >> Chemistry for Kids The Periodic Table is a way of listing theelements. Elements are listed in the table by the structure of their atoms. This includes how many protons they have as well as how many electrons they have in their outer shell.

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