Chapter 6 Classification of Matter

Transcription

1 Chapter 6 Classification of Matter Pure substances can be classified into two types elements cannot be broken down into other pure substances are made up of only one type of atom only 115 known elements today properties of each element is different from those of every other element atoms are like letters in the alphabet; they are the building blocks upon which all matter is built. compounds can be broken down into elements: they are combinations of elements these are not mixtures they have NEW properties totally different from the elements from which they are made. when two atoms combine together, they form molecules compounds (molecules) are like words made up of elements (atoms) 1

2 Consider the following: sodium and chlorine (see Periodic Table of the Elements) 2 sodium atoms 1 chlorine molecule 2 sodium chloride molecules sodium is a dangerous, highly reactive metal that burns when it touches water. chlorine is a green, highly poisonous gas. when they react and combine they form a white crystal that you put on your french fries! How many differences can you see between the start materials and the finish materials? A chemical formula is a short-hand sentence that uses symbols and numbers to describe what kind of elements and how many of each element is present in each molecule of a compound. Check out the table 2

3 Common name Elements combined into compound Chemical of compound formula water hydrogen oxygen H 2 O table salt sodium chlorine NaCl carbon dioxide carbon oxygen CO 2 glucose carbon hydrogen oxygen C 6 H 12 O 6 chalk calcium carbon oxygen CaCO 3 baking soda sodium hydrogen carbon oxygen NaHCO 3 copper sulphate copper sulfur oxygen CuSO4 How many of each atom are in? Review 6.1 In class Changes in Matter in chemistry there are two basic flavours: chemical new substances with new properties are produced molecules are rearranged into new ones 3

4 appearance change change is not easily reversed physical no new substances or properties are observed appearance change change is easily reversed How can you tell the difference between the two? In chemical usually one or more of the following occurs: 1. a new colour appears 2. heat or light is given off 3. bubbles of gas are produced 4. difficult to reverse (again, i know!) Review 6.2 Properties of matter Quanititative when you use numbers to describe quantity. (weight, volume, time, melting point, density etc.) Qualitative when you use your 5 senses to describe quality. (colour, slipperiness, smell etc.) 4

5 melting point the point at which a pure substance changes from solid state to liquid state. (e.g. water =?) freezing point - the point at which a pure substance changes from liquid state to solid state. (e.g. water =?) boiling point - the point at which a pure substance changes from liquid state to vapour state. (e.g. water =?) What state am I in? substance melting boiling state at 20 o C point point ( o C) ( o C) alcohol copper oxygen salt sulfur water density how much a unit (one!) volume of a material weighs usually measured in grams cm 3 marshmallow wood water iron 5

6 Which one of these four items of equal volume (1 cm 3 ) weighs the most? The least? Which one of these four items of equal volume (1 cm 3 ) has the greatest density? The least? How could you qualitatively test them? How could you quantitatively test them? Calculating density Find the mass of the object (scale) Find the volume o By multiplying depth X height X width o By displacement of water in a graduated cylinder Calculate density by density(d) = mass(m) volume (v) Method 1 h w d 6

7 Method 2 Review 6.3 7

8 6.4 Mixtures All matter can be classified into one of the following categories in this chart: Matter Mixtures Pure substances Mechanical Suspensions Solutions Element Compounds clumping of partial clumping particles of different one type of two ore more substances of one of the substances are atom types of atoms substances completely mixed combined together 8