Lesson 11: Describing Matter

Chapter 4: Lesson 11: Describing Matter You can understand what matter is by learning about the properties of atoms, elements, molecules, and compounds.Element- substance that cannot be broken down into another substanceAtom- the smallest particle of an element that has the properties of that elementNucleus- the center of an atom; most of the mass of the atom is in the nucleusMolecule- a particle made of two or more atoms that are joined togetherCompound- a substance made when the atoms of two or more compounds join together in a fixed ratioChemical Symbol - for an element is the combination of one or two letters that represents the element Matter is anything that takes up space and has mass. Look around your classroom. You, your pencil, your desk, and even the air are made of matter. All matter is made of elements. An elementis a substance that cannot be broken down into another substance. Each element has its own individual properties. An element like gold or silver is a shiny metal. An element like helium is an invisible gas. Chemical symbols are used to represent the elements. Each symbol contains one or two letters. Look at the table to find the chemical symbols of some of the common elements.ElementChemical SymbolHydrogenHOxygenOChlorineClSodiumNaNitrogenNCarbonC There are over 100 different types of elements found in nature. Every element is made of atoms. An atom is the smallest particle of an element that has the properties of that element. Any two atoms of hydrogen have the same properties. But an atom of hydrogen is different than an atom of oxygen. The nucleusis the center of an atom. Most of the mass of an atom is in the nucleus. An atom is too small to be seen with your eyes. Scientists have invented very powerful microscopes to see atoms. This is a picture of an atom. In the middle of the atom is the nucleus, which is made of particles called protons and neutrons. Smaller particles called electrons orbit the nucleus. Two or more atoms can combine to make a new particle called a molecule. Atoms from the same element can form a molecule. A molecule of oxygen gas is made from two oxygen atoms. Atoms from different elements can also combine to form a molecule. One carbon atom and two oxygen atoms form a carbon dioxide molecule. The table below shows four types of molecules found in air. The formula of a molecule shows the type and number of atoms present in a molecule.MoleculeFormulaMade FromMolecules Made from the Same ElementsOxygen gasO22 oxygen atomsNitrogen gasN22 nitrogen atomsMolecules Made from the Different ElementsCarbon dioxideCO21 carbon atom and2 oxygen atomsWaterH2O2 hydrogen atoms and1 oxygen atomA compoundis formed when atoms of two or more elements combine in a fixed ratio. The smallest particle of a compound is a molecule. Carbon dioxide gas is a compound. It is made from two different types of elements that always combine in a fixed ratio. The formula of a carbon dioxide molecule, CO2, shows that one carbon atom joins with two oxygen atoms. Water is also a compound, made from hydrogen and oxygen. Every molecule of a compound is made of the same combination of elements. That means every molecule of water is made of two hydrogen atoms and one oxygen atom. Every molecule of carbon dioxide is made of one carbon atom and two oxygen atoms. A molecule of oxygen gas is made of two oxygen atoms. But oxygen gas is not a compound. In a compound, at least two different types of atoms join together. Can you mix two substances together to make an element? Explain why or why not. Which element is represented by Na? Can two atoms of oxygen have different properties? yes no What is a molecule? How many atoms are present in a molecule of carbon dioxide? What are they? Why is water a compound? What is the difference between a compound and an element? All matter has mass and takes up space. Give an example to show that gas takes up space. Nitrogen gas is made of two nitrogen atoms. Is nitrogen gas a compound? yes no Which of the following is not a compound? salt oxygen gas water carbon dioxide A molecule of nitrogen gas is made from - one nitrogen atom one nitrogen atom and one oxygen atom two nitrogen atoms two nitrogen atoms and one oxygen atom It is not true that water is - composed of atoms an element composed of molecules a compound The picture below shows the molecule of which compound? water oxygen gas carbon dioxide protons and electrons Which of the molecules in the diagram is a compound? only the chlorine molecule only the carbon dioxide molecule both the gold molecule and the carbon dioxide molecule neither the gold molecule nor the carbon dioxide molecule