Elements ,compounds, and mixtures Juwarto, S.Pd Grade VII Semester 1 115 Junior high Schools
Basic Competency: To understand the element, compound and mixture.Standard Competency: Describes concept of element, compound and mixture.Objectives:• To describe the characteristics of elements, compounds, and mixtures• To classify matters into elements ,compounds ,and mixture
• Matter - anything that has mass and take any space
• Element is single matter that cannot be broken down into simpler matter by chemical methods. • There are 116 known elements. Of these 92 are found in the Earth (natural). The other 24 elements have been made by scientist in laboratories (manmade).Examples of element: silver Fluorine Gold Aluminium Mercury
The Symbol of element• Jons Jacob Berzelius proposed alphabets as the symbols of each element.• All of elements use symbol. These symbols were taken one or two letters from their old Latin or Greek name. Example: Au is the Latin word of gold “Aurum”.• Rules of writing element symbols: 1. If an element is symbolized by one letter, it must be capital letter, for example oxygen (O), hydrogen (H), carbon (C). 2. If an element is symbolized by more than one letters, the first letter must be capital letter followed by small letter, for example zinc (Zn), gold (Au), copper (Cu).
Think Time• What are the chemical symbols of the following elements? a) Bromine f) Mercury b) Silver g) Calcium c) Uranium h) Natrium d) Antimony i) Potassium e) Tungsten j) Helium• What are the names of the elements with the following chemical symbols? a) Si f) Ni b) P g) Al c) Sn h)Mg d) Pb i) Zn e) Au f) S
Classification of the Elements Classification of elements by state – Elements can be classified by their physical state at room temperature • Solid (of the 92 natural element, 79 are solids) • Gas (of the 92 natural element, 11 are gases) • Liquid (of the 92 natural element, 2 are liquid) Chlorine gaseous Silver solid element Bromine liquid element element
Classification of elements as metal and non – Elements are classified as metals and non-metals, depending metals on how well they conduct electricity and heat. – Metals are good conductors and Non-metal very poor electrical conductors. – Some elements are classified as Metalloids (or semi-metals). Metalloids have properties between those of metals and non metals. Metalloid metal Non - metal lead carbon sulphur boron mercury silikon copper chlorine neon Noble gases
Properties Metals Non-metalsAbility to conduct Good conductor Poor conductorheat and electricity (except carbon)Densities, melting Usually solids Usually liquid andand boiling point (except gases with low mercury), high densities, low densities, high melting points melting points and boiling points and boiling pointsAppearance Usually hard and Usually soft and shiny dullAre they Yes Nomalleable?(mudah ditempa )
Classification of elements as in the periodic table
What are elements made of?• Atoms An atom is the smallest unit of an element, having properties of that element. The atoms of one element are different from the atoms of any other element. For example, all hydrogen atoms are the same and are different from atoms of carbon or iron.• Molecules Most gaseous elements form molecules comprising two atoms. Example: – Oxygen (O2), N2 Gases – Hydrogen (H2), – Nitrogen (N2), N + N N N – Chlorine (Cl2)
Post testAnswer this question.• Define an element.• State the names and symbols of some common elements.• Describe ways of classifying the elements. www.chem4kids.com
• Compound is a substance containing two or more elements chemically joined together.• Compound is a single matter that cannot be broken down by physical separation.• The compound can only be broken down into its elements by a chemical reaction.
Ifelements combine together, they will completely change. For example: Water (H2O) is a compound made up of Hydrogen and Oxygen. Hydrogen and Oxygen are colourless gases, and the compound water is colourless liquid H H + O H O H
What are Compound made of? Molecules is the smallest particle of a compound. A compound contain only one kind of molecule. Molecule is a group of two or more atoms chemically joined together.
The chemical formula of a molecule shows thenumber and kinds of atoms contained in it. The chemical formula for water is Symbol of atom The amount of atoms present in one moleculeThis formula tells us that a water moleculecontains 2 hydrogen atoms and 1 oxygenatom
1. State the number of atoms and name the kinds of atoms shown by each formula a. Alcohol, C2H5OH b. Refined sugar, C12H22O11 c. Sulphuric acid, H2SO4 d. Sulphur dioxide, SO2 e. Glucose, C2H12O6 f. Urea, CO (NH2)2
Names of compound• Many compound contain a metal and a non-metal. The metal part usually comes first, followed by the non-metal part. – For example: NaCl (sodium chloride)• The names of many compounds with only two elements often end in –ide. – For example: MgO (magnesium oxide)• If the name of compound end in –ate, they contain oxygen. – For example: CaCO3 (Calcium Carbonate)• Acids are compounds. Their names usually end in –ic acid. – For example: HCl (Hidrochloric acid)
These are some of the chemical formula Compound Chemical Formula Sodium Chloride NaCl Magnesium Oxide MgO Sodium hydroxide NaOH Calcium carbonate CaCO3 Sulphuric acid H2SO4 Water H 2O Ammonia NH3 Carbon dioxide CO2 Sucrose (sugar) C12H22O11
Chemical reaction between hydrogen and oxygen producing waterN BEFORE REACTION AFTER REACTIONo Hydrogen Oxygen Water produced Excess1 1 gram 8 gram 9 gram None2 2 gram 16 gram 18 gram None3 2 gram 8 gram 9 gram 1 gram of hydrogen4 2 gram 17 gram 18 gram 1 gram of oxygen5 3 gram 30 gram 27 gram 6 gram of oxygen 1. Calculate the comparison between the mass of hydrogen and oxygen in water compound. What is the result? 2. What will happen if the mass of hydrogen and oxygen reacting does not follow the comparison? 3. What can you conclude about the comparison of elements in the compound?
Conclusiona. Water was compound by hydrogen and oxygen with ratio of 1:8 (1 for hydrogen and 8 for oxygen)b. If the ratio of H:O was not equal to 1:8, there would be an excess element (sisa)c. The mass of elements before and after a mass ratio of elements of a “The reaction was CONSTANT compound component is constant” (Perbandingan massa unsur-unsur penyusun senyawa adalah tetap)
Think Time1. When 4 grams of hydrogen react with 16 grams of oxygen, how many grams of water are produced? If there is an excess, determine the element and it massAnswer:• The comparison for the mass ofN hydrogen and oxygen is 1:8 Before reaction After reactiono Hydrogen Oxygen Water produced Excess1 4 gram 16 gram 18 gram 2 gram of (2 gram of hydrogen and 16 Hydrogen gram of oxygen)
• In the world, there are many things that’s not pure substances.• Mixtures consist of two or more substances that are not chemically joined together.• Mixtures can consist of elements, compound or both. Also the substances in a mixtures may be solids, liquids or gaseswater is mixture of Sea compounds including water Brass is a mixture of the and sodium chloride elements copper and zinc
Heterogeneou Homogeneou s sThe prefixes "homo"- indicatesameness The prefixes: "hetero"- indicateA homogeneous mixture has the difference.same uniform appearance and A heterogeneous mixture consistscomposition throughout. Many of visibly different substances orhomogeneous mixtures are phases. The three phases or statescommonly referred to as of matter are gas, liquid, and solid.solutions. In sugar solution, sugar is the solute and water is the solvent
Compound MixturesComposition Has a fixed composition Has a variable by mass composition by massMelting and Has fixed melting and Has variable meltingBoiling point boiling points and boiling pointsProperties Has it own properties Does not usually have which are different from its own properties; it its elements has the same properties as its componentSeparation Cannot be separated by Can be easily physical means. separated into its Chemical reaction is components by needed to separate the physical means. elements
Identify each of the following diagrams as an atom, molecule, element, compound or mixture.
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