Elements and Compounds

Transcription

1 Elements and Compounds Part I: Matter What is matter? Matter is everything that you can see, touch, taste, and feel. Anything that has mass and takes up space is matter. Mass measures how much matter is in an object and volume measures how much space the matter occupies. What are some examples of matter in the classroom? Matter can be made from only one kind of material, or it can be a mixture of different kinds of materials. Think about the examples of matter that the class identified. Which examples are only one kind of matter? Which examples are a mixture of different types matter? When matter is made of different types of materials it is called a mixture. When matter is made of only one kind of material, it is a pure substance. A pure substance is matter that is uniform throughout and has consistent properties. All matter is made up of very small particles called atoms. Atoms are the building blocks of all matter. When a substance contains only one type of atom, it is called an element. Each element has a special name and unique properties, different from all the rest of the elements. All known elements are organized on a chart called the Periodic Table of Elements. An element is a pure substance and made of only one type of atom; it cannot be broken down into a simpler substance. Take a look at the Periodic Table of Elements provided by your teacher. You will see many boxes that contain information for each of the elements. The first box is for the element hydrogen. The name of this element is hydrogen. The name of an element can be found at the bottom of the box. Every element is also represented by a chemical symbol, a one or two letter symbol. When the element is represented by two letters, the first letter is always capitalized and the second letter is lower case. The chemical symbol of hydrogen is. Chemical Symbol Element Name ydrogen Answer questions 1 through 5 in your Student Journal.

2 Part I: Matter, continued Now you will practice writing chemical symbols and discover the elements that make up Earth s atmosphere, lithosphere (solid earth), biosphere (living matter), and hydrosphere (oceans). 1. Your teacher will supply you with an element card providing information about one element. Find the element on the chart in your Student Journal. 2. Use the Periodic Table to determine the chemical symbol of each element card. Record the chemical symbol on the chart in your Student Journal. Then use the element card to place an X in the box if the element is found in significant amounts in the lithosphere, biosphere, hydrosphere, and/or atmosphere. Shaded area(s) on the card indicates the element is present in significant amounts. 3. On your teacher s signal pass your card on to the next student. 4. Continue recording and passing cards according to the teacher s signal until the entire table titled Elements Found in Significant Amounts is complete. Answer Questions 6-10 in your Student Journal. Part II: Elements, Compounds, and Mixtures When you were in elementary school, you learned about mixtures. Remember that the properties of the mixture depended on the parts of the mixture. For example, salt water is wet like water and salty like the salt. Salt water keeps the properties of its ingredients because it is a mixture. Mixtures can be separated by simple mechanical methods like sorting, evaporation, filtering, or magnetic attraction. Matter that is a pure substance is very different from mixtures. Pure substances are made from only one type of matter and cannot be separated by physical methods. Pure substances can be divided into two categories, elements and compounds. You already know that elements are pure substances that cannot be broken down into simpler substances. When elements combine, they form new substances called compounds. Compounds have entirely new properties, different from the properties of the elements that it contains. Compounds are pure substances made of two or more kinds of atoms bound together. Compounds can also be broken down into simpler substances. Complete Part I in your Student Journal. Continue 2 to the next page of this Student Guide. 2

3 Part II: Elements, Compounds, and Mixtures, continued Your teacher will provide you with a set of boxes containing information about Elements and Compounds. Cut apart each box then sort them into the correct columns in your Student Journal chart titled: Elements, Compounds, and Mixtures, Oh My! int: Look at the information given in the Mixture Column first. Glue all in place after checking with your teacher. Part III: Elements Make Compounds Perhaps you sometimes refer to water using its chemical name: 2 0 or O is the chemical name of water that identifies the building blocks of water. What element has the chemical symbol? What element has the chemical symbol O? The compound water is made of the elements hydrogen and oxygen. ydrogen and oxygen each have their own distinctive properties such as: freezing and boiling temperatures, color, and mass. The properties of water are very different from the properties of hydrogen and oxygen. O Carbon dioxide is another compound that is familiar to you because it is the gas that you exhale with each breath. You may have heard carbon dioxide referred to as C-O-2 or CO 2. The O in CO 2 is the same oxygen element that you find in water. You may already know the name of the element that C stands for, but if you did not know the name, you could look it up in the Periodic Table of Elements. What does the C in CO 2 represent? The small number 2 in CO 2 represents the number of atoms of oxygen that are in carbon dioxide, two oxygen atoms. The C in the CO 2 is not followed by a small number so that means there is only one atom of carbon in carbon dioxide. This small number is called a subscript O Complete Part II in your Student Journal. Continue 3 to the next page of this Student Guide. 3

4 Part III: Elements Make Compounds, continued Your teacher will provide you with Unifix cubes in four different colors, four index cards (two labeled compound and two labeled element) and a beaker. The cubes represent atoms of the elements carbon, oxygen, hydrogen and copper. 20 blue = 20 oxygen; 4 red = 4 carbon; 8 yellow = 8 hydrogen; 4 green = 4 copper 1. First make oxygen gas, or O 2, by connecting two blue cubes. Is O 2 an element or compound? Recall that an element is a pure substance made of only one kind of atom, so O 2 is an element. Use the blocks to make three more individual models of O 2 and set these models aside to use later. 2. Next use the blocks to make a model of carbon dioxide, or CO 2. Is carbon dioxide an element or a compound? Carbon dioxide is a pure substance made from two different elements so it is a compound. Use the blocks to make three more individual models of carbon dioxide, CO 2, and set these models aside to use later. 3. Now use the blocks to make a model of the compound water, 2 O. ow do you know by just looking at this model that it is a compound? Compare the single model of water to the models of oxygen that you made earlier. These models clearly represent when a substance is an element or a compound simply by looking at their colors. Make three more models of water. 4. Leave the individual atom models of the element copper in a pile. Identify the models that you created as elements or compounds by placing a labeled index card next to the appropriate set. Complete the chart in Part III of your Student Journal. 5. All four sets of models that you made are pure substances! Recall that a pure substance is uniform throughout and has consistent properties such as melting or freezing points, hardness, and whether or not the substance burns (flammability). 6. Use any combination of the pure substances that you modeled to create a mixture by placing them in a beaker. Your mixture will probably not look like the mixtures created by other groups. Recall that mixtures can vary in the amounts and types of matter present, which explains why mixtures do not have consistent properties. Complete Part III in your Student Journal. 4 4

5 Part IV: Analyzing Compounds As a final activity, use your experience with the Unifix cubes as model atoms in elements and compounds. Find the list of six compounds in your Student Journal on the chart titled: Analyzing Compounds 1. Use your Periodic Table to determine the elements that are found in each of the compounds listed on the chart. 2. Write the element names and the chemical symbols that appear in the compound in the first column of the chart. (The first one has been done for you.) 3. Your teacher will give you printed chemical symbols on paper. Cut apart these model atoms of the elements that are found in the listed compounds. 4. Work with your partners to make a model of each compound. Remember subscripts, the small number to the lower right of an element means there are that number of atoms in the compound. Glue your model in place in the space provided on the chart titled: Analyzing Compounds. Complete Part IV and the Reflections and Conclusions in your Student Journal. 5 5