Grade 7 General Science PDF

1.1 The Nature of Science and its Branches ------------------------------------------ - Define science as a body of knowledge and the processes and practices used to add to that body of knowledge. - Distinguish between the Indigenous Science and Conventional Science. - Describe the main...

1.1 The Nature of Science and its Branches ------------------------------------------ - Define science as a body of knowledge and the processes and practices used to add to that body of knowledge. - Distinguish between the Indigenous Science and Conventional Science. - Describe the main branches of science. - Explain the relationship among the branches of science. - Explain how the development of science and technology affect one's beliefs, practices, and ways of thinking. - Identify the significant contributions of Ethiopian and International Scientists in science and technology. - Discuss the importance of scientific values in decision making and problem solving. - Discuss the importance of ethical disciplines in scientific investigations. **Activity 1.1** +-----------------------------------------------------------------------+ | **Activity 1.2** | | | | Perform the following activities. | | | | Find some practical indigenous knowledge in your community that | | solves community problems and present your finding to your class | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ - extractions of medicinal chemicals from plants to treat disease and fight infections. The common medicinal plants used for treating and curing various disease are: Hagenia Abyssinica (Kosso tree) , Eucalyptus globulus (bahrzaf), and Ocimum lamiifolium Hochst - preserving meat by adding a salt and smoke drying. +-----------------------------------------------------------------------+ | **Activity 1.3** | | | | Form a group and discuss the following questions. Then share your | | ideas to the class | | | | 1.What are the major branches of science? | | | | 2\. Give short descriptions of physics, Chemistry and Biology. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ - Biology is a branch of natural science which studies about living things. - **Biophysics:** a combination of Biology and Physics. It is the study of physical phenomena and physical processes in living things, on scales spanning molecules, cells, tissues and organisms. - **Biochemistry:** combination of biology and Chemistry. It is the branch of science that explores the chemical processes within and related to living organisms. It involves the study of chemical reaction in living things. Figure1.2.The relationships between some fields of Natural Science 1. What is science? 2. List the three branches of natural science 3. Which field of science studies about matter and energy? 4. What is the difference betwen biophysics and biochemistry? Grade 7 General Science General Science Grade 7 +-----------------------------------------------------------------------+ | **Activities 1.4** | | | | **Form a group and do the following activity** | | | | Choose one of the scientists and create a role-play for the press | | release following the news of his/her discovery. Various roles to | | consider would include: the scientist; media; fellow scientists; and | | the general public. Alternatively, you could choose an Ethiopian | | scientist and create a cartoon strip showing their discovery. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ fever disease or bilharzia. He found that berries from the endod plant, which is commonly used to make soap and shampoos in many parts of Africa, is a potent, inexpensive and safe molluscicide, to prevent the spread of the parasitic worm. This discovery made the plant an object of scientific research in many parts of the world.  **Prof.Yalemtsehay Mekonnen** was born in Asela, Ethiopia on May 30, 1955. She work on human physiology, the impact of pesticides on human health, the use of plants as medicinal against human and animal disease and as the first female professor of Addis Ababa university. Grade 7 General Science **Dr. Tewolde Berhan Gebre Egziabher** ---------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ is an Ethiopian scientist, who has worked to ensure biodiversity and the rights of communities to their genetic resources. is an Ethiopian scientist, plant breeder,geneticist and Professor at Purdue University. In 2009, he won the World Food Prize for his major contributions in the production of new strain of sorghum. +-----------------------------------------------------------------------+ | **Activity 1.5** | | | | Form a group and discuss on the following questions then present your | | opinion to the class | | | | i. Do you think ethical discipline is important for science? | | | | ii. List down some ethical disciplines in science | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ **Exercise 1.2** 1. The natural science disciplines are A. B. 2. The branches of natural science studying the composition of compounds and the processes taking place in organisms, respectively, are: C. 3. Which one of the following is true about Science? D. E. D. All are correct 4. Which one of the following is true about Indigenous knowledge? A. It is based on scientific method. B. The knowledge derived from western countries. C. It incorporates local people's knowledge. D. It has universal perspective and commonly recognized as western science. 5. Which one of the following is the World famous scientists who discover law of motion and gravity? F. G. ### 1.2 Common laboratory Equipment, Uses, Safety Rules and #### Procedures in Science laboratories - Identify different laboratory tools - Demonstrate safe ways of using apparatus in the laboratory. - Practice precautionary measures in the laboratory - Exhibit knowledge of lab safety rules and procedures. - Identify potential hazards and implement appropriate safety procedures when conducting laboratory ###### 1.2.1. Common Laboratory Equipment +-----------------------------------------------------------------------+ | **Activities 1.6** | | | | Form a group and perform the following task. From locally available | | materials produce laboratory tools such as beaker, measuring | | cylinder, balance, tong, etc. and present its use to the class. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ ------------ ------------------------ ----------------------------------------------------------- Picture Uses Obtaining the mass of an object Holding water (also used to heat liquid Transporting a hot beaker; and removing lid from crucible Used to measure temperature Test tubes Holds small amounts of liquids for mixing or heating. Petri dish  To grow and count bacteria Marked with milliliter (ml) cylinder scale and is used to measure volume Heating (flame-safe) contents in the lab ------------ ------------------------ ----------------------------------------------------------- ###### 1.2.2 Laboratory Safety Rules +-----------------------------------------------------------------------+ | **Activities 1.7** | | | | i\. List down some laboratory safety rules ii. Discuss hazard | | symbols on chemical bottles, electrical gadgets and other materials | | found in the laboratory | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ - Dress appropriately (goggles, gloves, shoes andlaboratory coats). - Tie back loose hair. - Know the locations of safety equipment like fire extinguisher. - Know what to do in case of an accident. - Do not taste or smell chemicals. - Do not eat or drink in laboratory. - Never add water to concentrated acid solutions. Alwaysadd acid into water. - Carry out only the experiments assigned by your teacher. - Dispose of all chemical wastes properly. ###### 1.2.3 Science Laboratory Safety Symbols and HazardSigns, Meanings ###### 1.2.4 Writig a Laboratory Report A. Knowing the hazards of the materials being used B. Reading the labels on the reagent bottle carefully C. Wearing any type of cloth and shoes D. Not using laboratory glassware for eating or drinking purposes. 2. Which of the following laboratory tool is used for the approximate measurements of volume of liquids A. Test tube B. Thermometer C. Measuring Cylinder D. Dropper 3. The type of laboratory equipment categorized under measuring equipment is E. Bunsen burner B. Triple-beam balance - Science is a systematic method of gaining knowledge about the physical and natural world and the social aspect of human society. - Indigenous science is process by which Indigenous people build their empirical knowledge of their natural environment - Conventional science is the system of knowledge which relies on certain laws that have been established through the application of the scientific method to phenomena in the world around us. - Science has two major categories, which are natural science and social science. - Natural science has three branches which are Biology, chemistry and physics. - Technology is the use of scientific knowledge to help human beings work easier and live better as well as enjoy their environment more. - A person who studies technology is called a technologist. - Science and technology plays an important role in our daily life - Some famous scientists in Ethiopia are Dr. Aklilu Lemma, Dr. Tewolde Berhan Gebre Egziabher , Prof.Gebisa Ejeta , and Prof.Yalemtsehay Mekonnen - Famous scientists from the world are Albert Einstein, Michael Faraday. Marie Curie and Isaac Newton etc. - Laboratory equipment comprises different sets of apparatus, which are designed to perform various tasks in the laboratory. - Knowing Laboratory safety rule is very important to reduce risks faced during laboratory investigation. Review Exercise --------------- 1. Natural science is the study of nature and natural laws. 2. Biology, Physics and chemistry do not share common areas of study. 3. Technology makes life easier or more pleasant and work more productive. A. Chemistry C. Biology B. Physics D. Geology A. Chemistry C. Biology B. Physics D. Geology 3. The famous Ethiopian scientist who discovered a natural treatment to Schistosomiasis or bilharzia disease. A. Dr. Tewolde Berhan Gebre Egziabher B. Dr. Aklilu Lemma C. Prof. Gebisa Ejeta D. Prof. Yalemtsehay Mekonen 4. Which of the following is NOT a laboratory safety rule? A. You should tie back loose hair. B. You should add water to Acid. C. Do not suck solution in the pipette by mouth. D. When lighting a Bunsen burner, you should light the match stick before turning on the gas. E. Theory C. Observation F. Natural law D. Science 1 Combination of Biology and Physics A Biochemistry 2. Combination of Geology and Physics B. Physical Chemistry 3. Combination of Biology and Chemistry C. Biophysics 4. Combination of Chemistry and Physics D. Geo-physics 1. Define technology 2. What is the difference between science and technology? 3. Mention the steps to write laboratory report. 4. Why ethics in science is important? Unit 2 MATTER IN OUR SURROUNDINGS ================================= +-----------------------------------------------------------------------+ | At the end of this unit, you will be able to: | | | | - Use particles theory's postulates to explain properties and | | behaviour of materials. | | | | - Classify matter as an element, compound, homogeneous mixture, or | | heterogeneous mixture with regard to its physical properties. | | | | - Describe the structure of solids, liquids and gases in terms of | | particle separation, arrangement and types of motion. | | | | - Differentiate between physical and chemical properties and | | changes of matter. | | | | - Distinguish between chemical and physical of matter. | | | | - appreciate that matter can be classified based on physical or | | chemical properties. | | | | - Use properties of matter to identify substances and to separate | | them. | | | | - Access information, using a variety of sources. | | | | | | | | - Demonstrate scientific inquiry skills along this unit: observing, | | classifying, comparing and contrasting, making mode, inferring, | | communicating, asking questions, designing experiments, drawing | | conclusions, applying concepts. | +-----------------------------------------------------------------------+ ### 2.1. Characteristics and nature of matter - Define matter with examples from day today life. - Demonstrate that matter is made up of tiny particles. - State the postulates of the particle theory of matter. - Infer the particulate nature of matter from demonstration / investigation. - Apply particle nature of matter in explaining diffusion and every day effect of diffusion. +-----------------------------------------------------------------------+ | - Describe and/or make a representation of the arrangement, | | relative spacing, and relative motion of the particles in each of | | the three states of matter. | | | | - Describe and explain compression in terms of distance | | betweenparticles. | | | | - Use the terms melting, evaporating, condensing, and freezing/ | | solidification to describe changes of state. | | | | - Use the particulate nature of matter to explain: melting, | | freezing/ solidification, evaporation, condensation. | +=======================================================================+ | | +-----------------------------------------------------------------------+ | **Activity 2.1** | | | | 1. Describe matter by your own words? | | | | 2. Consider the followings: air, light, soil, plant, water, sound, | | table and heat. Try to classify them as matter and non-matter. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ a. Air e. Gold i. Silver b. Pizza f. Virus j. Cake c. Sound g. heat k. Water d. Light h. Bacteria l. Magnesium **Activity 2.2** 1. Inflate a balloon and observe its shape in the class room. 2. Make observations while wind blowing leaves, or dust in your surroundings. Based on the above activity, work on the given question below a. What do you think that matter is made of? b. How do the particles move around in space? **Activity 2.3** 1. Everything is made of \_\_\_\_\_\_\_\_\_\_\_\_. 2. Particles are always\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. 3. An increase in \_\_\_\_\_\_\_\_\_\_\_\_makes particles move\_\_\_\_\_\_\_\_\_. 4. An increase in\_\_\_\_\_\_\_\_\_\_\_\_ is the same thing as an \_\_\_\_\_\_\_\_\_ in energy. 5. The particles in hot water have\_\_\_\_\_\_\_\_energy than\_\_\_\_\_\_\_\_\_ water. 6. The particles in ice move \_\_\_\_\_\_\_\_\_\_\_\_ than particles in \_\_\_\_\_\_\_\_\_\_\_. 1. All matter is made up of tiny particles. 2. The particles of matter move continuously. 3. The particles have spaces between them. 4. Adding heat to matter makes the particles move faster. 5. There are forces between the particles. 6. Particles of one substance differ from the particles of other substance. ##### Diffusion in Daily Life 1. Take a bottle of perfume and open it in one corner of the room and record how long it takes to reach to different students at different distances to smell it. 2. Add 2 or 3 drop ink into a beaker of water using a pipette and watch the ink diffuse to color the water. 3. Record your observation for the above to experment **Observation and analysis** 1. Complete the blank space from the word box **Diffusion low scent high** 2. Arrange in an increasing order of the rate of diffusion of solids, liquids and gases. ###### 2.1.5 Properties of Solids, Liquids and Gases +-------------+-------------+-------------+-------------+-------------+ | | Physical | | | | | | states | | | | +-------------+-------------+-------------+-------------+-------------+ | | Gases | Liquids | Solids | | +-------------+-------------+-------------+-------------+-------------+ | | -disorderly | -Less | -Orderly | | | | | orderly | arranged | | | | arranged | arranged | | | | | | particles | (regular | | | | -particles | are | pattern) | | | | are very | relatively | -Particles | | | | far apart | close to | are very | | | | | each other | close to | | | | -almost no | -Have | each other | | | | attractive | relative | | | | | force | attractive | | | | | between | force | | | | | particles | between | | | | | | particles | | | +-------------+-------------+-------------+-------------+-------------+ | | -flow(move) | flow | -Do not | | | | freely | together in | flow or | | | | | random | | | | | -flow | motion -are | move | | | | together in | known as | | | | | | fluids | -Vibrate in | | | | random | | a fixed | | | | motion -are | | position | | | | known as | | | | | | fluids | | | | +-------------+-------------+-------------+-------------+-------------+ | | Highly and | Compressibl | Not | | | | easily | e | compressibl | | | | compressibl | to a very | e | | | | e | small | | | | | | extent | | | +-------------+-------------+-------------+-------------+-------------+ | | -Have no | -Have no | -Have | | | | definite | definite | definite | | | | | | Shape and | | | | Shape and | Shape | volume | | | | volume | | | | | | -Assume the | -Assume the | | | | | shape of | shape of | | | | | the | the | | | | | container | container | | | | | and | | | | | | entirely | -have | | | | | fill it. | definite | | | | | | | | | | | | volume | | | +-------------+-------------+-------------+-------------+-------------+ | | Have very | -Have low | -Denser | | | | low | density | than all | | | | | | -Condensed | | | | density | than solids | state than | | | | than | | all | | | | liquids and | -Condensed | | | | | solids | state | | | | | | compared to | | | | | | gases | | | +-------------+-------------+-------------+-------------+-------------+ | | Exert | Exertpressu | Exert | | | | pressure | re | pressure | | | | | towards | towards | | | | equally in | depth. | gravity | | | | all | | | | | | direction | | | | +-------------+-------------+-------------+-------------+-------------+ | | Diffuse | Diffuse | Difficult | | | | | very slowly | to diffuse | | | | spontaneous | in random | | | | | ly | motion | | | | | in all | | | | | | directions | | | | | | with random | | | | | | motion | | | | +-------------+-------------+-------------+-------------+-------------+ | | | | | | +-------------+-------------+-------------+-------------+-------------+ I. **Give short answers** 1. What are the three states of matter? 2. List the properties of solids. 3. Name a property of liquids that do not share with solids. 4. Name a property of gas that do not share with liquids. 5. Give a characteristic that is the same for liquids and solids. 6. Give a characteristic that is the same for gases and liquids. 7. Which state of matter can not be poured? 8. Which state of matter can be compressed easily? II. **Choose the correct answer for the following questions.** 9. Which state of matter is fluid? A. solid B. Liquid C. Gas D. B and C 10. In which state of matter are particles close together? B. solid B. Liquid C. Gas D.all ##### 2.1.6. Changes in State **Activity 2.5** **D C** ### 2.2. Physical and Chemical Properties of Matter - Describe physical Properties. - Use physical properties of matter to identify substances. - Conduct experiments to identify properties of substances and make group report. - Identify chemical properties. - Distinguish between physical and chemical properties. ###### 2.2.1 Physical properties of matter +-----------------------------------------------------------------------+ | **Activity 2.6** | | | | Perform the following tasks in groups and present your conclusions to | | the class. Given the following physical properties of substances: | | odor, color, taste, melting point, boiling point and density. | | | | 1. Which of these physical properties have constant values under | | specific condition, such as temperature? | | | | 2. Which physical properties can be recognized directly by our sense | | organs? | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ 3. Which of these properties are measured using instruments? 4. What will happen to ice kept in a cup in the classroom? 5. Which sense organs help us to detect color, odor and taste? 6. How do you describe the taste of lemon? ##### 1. Physical Properties Detected by Sense Organs **Caution!** ------------------------------------------------------------------- -------------- -- Care has to be taken in smelling substance as they may be harmful +-----------------------+-----------------------+-----------------------+ | Tasting can be used | | | | to identify | | | | substances only if | | | | the substance to be | | | | tasted is not | | | | harmful. | | | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ | **Activity 2.7** | | | | | | | | You are allowed to | | | | taste some acids in | | | | the forms of citric | | | | acid that are found | | | | in lemon and orange | | | | or acetic acid in the | | | | form of vinegar at | | | | home but you have | | | | never been allowed to | | | | taste any kind of | | | | acids in the | | | | laboratory. What is | | | | the reason? | | | | | | | | Discuss your finding | | | | in group and present | | | | to the class. | | | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ m=10g ρ = [m] 10g 3 = 20g/cm~3~ v 0.5cm V=0.5cm3 ###### 2.2.2 Chemical Properties of Matter +-----------------------------------+-----------------------------------+ | Physical properties | Chemical properties | +===================================+===================================+ | Propertiescan be measured or | Properties that describe how a | | observed without changing the | substance changes (or resists | | chemical natureof the substance. | change)to form anew substance. | +-----------------------------------+-----------------------------------+ | Easily identified. | Cannot be determined just by | | | viewing or touching the | | | substance. | +-----------------------------------+-----------------------------------+ | The composition or identity of a | The substance's internal | | substance not change. | structure must be affected for | | | its chemical properties to be | | | investigated. | +-----------------------------------+-----------------------------------+ | Examples: color, density, | Examples:Flammability | | volume,melting.boiling. | andreactivity | | | | | Conductivity. | | +-----------------------------------+-----------------------------------+ 1. Classify each of the following properties as a physical property or a chemical property. a. Iron metal rusts in an atmosphere of moist air. b. Mercury metal is a liquid at room temperature. c. Nickel metal dissolves in acid to produce a light green solution. d. Potassium metal has a melting point of 63°C. e. Copper metal possesses a reddish brown color. f. Titanium metal can be drawn into thin wires. g. Beryllium metal, when inhaled in a finely divided form, can produce serious lung disease. h. Silver metal shows no sign of reaction when placed in hydrochloric acid. i. Lead is denser than aluminum. j. Flammability of plastics. 2. Classify each of the following properties as an intensive property or extensive property. k. boiling point b. length c. mass d. Color e. density 3. Categorize the following physical properties as physical properties recognized by our sense organs or measurable physical properties ### 2.3 Classification of Substances - Use the particle theory to describe the difference between pure substances and mixtures. - Differentiate between elements and compounds. - Classify common elements into metals and non-metals. - Investigate the properties of metals and non-metals and compile a list of general properties. - Investigate the properties of non-metals and compile a list of general properties. - Describe and classify mixtures as homogeneous and heterogeneous. Use models/ particles diagrams to show differences between homogenous and heterogeneous. - Describe the relationship among elements, compounds, mixtures, homogenous mixture and heterogeneous mixtures. +-----------------------------------------------------------------------+ | **Activity 2.8** | | | | Perform the following tasks in groups and present your findings to | | the rest of the class. | | | | 1 Consider the following substances: chalk, bronze, sugar solution, | | iron, water, milk, oxygen, copper, gold, sugar, table salt, cooking | | oil, sulfur, air, silver, hydrogen, ink, chlorine and soil. | | | | Classify each of them under pure substance or mixture. Among pure | | substances, state whether it is an element or a compound. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ **MATTER** -- ------------ -- 2.3.1. A Pure Substance 2.3.2 Elements and compounds - They are shiny (lustrous) in nature. - They are good conductor of heat and electricity. - Their density and melting point is high. - Moldable (Malleable): malleability is the ability of a substance to be pressed into sheets when hammered. - Ductile: ductility is the ability to be drawn into thin wire. - Are solid at room temperature except mercury which is found in liquid state. ##### Activity 2.9 - they exist in two of the three states of matter at room temperature except bromine which exists as a liquid state. - they are not shiny (dull appearance), and are non-conductors of heat and electricity. - they have relatively, low melting points and boiling points. **Metals** **Non-metals** ---------------------- -------------------------------------------------- These exist in all three states These are soft except diamond These are brittle and can break down into pieces These are shiny These are non-lustrous except iodine Electronegative in nature Have high densities. Have low density 1. 2. 3. 4.  ##### 2.3.3. Mixtures **Activities 2.10** 1. Suppose a teaspoon of magnesium filings and a teaspoon of powdered sulfur are placed together in a metal beaker. Would this constitute a mixture or a pure substance? Suppose the magnesium filings and sulfur are heated so they react with each other, forming magnesium sulfide. Would this still be a "mixture"? Why or why not? 2. What is the difference between pure water and a solution of sodium chloride in water? 3. Do you think air is a pure substance or a mixture? Why? **Activity 2.11** Type of homogeneous Common examples --------------------- ------------------ ---------------------------------------------- Gaseous Gas in gas Air, mixture of oxygen and nitrogen Liquids Gas in liquid Soft drinks(Pepsi, Miranda, coca cola), beer Liquid in liquid Alcohol in water Solid in liquid Salt solution, sugar solution Solids Solid in a solid brass (Zn/Cu), Bronze (cu/Sn) Vinegar Steel Sugar solution Figure 2.11 Some common examples of homogeneous mixture **Activity 2.12** Soup Blood Soil Homogeneous mixture Heterogeneous mixture -------------------------------------------------- ------------------------------------------ It has a uniform composition It has a non-uniform composition It has only one phase There are two or more phase The constituent cannot be seen easily. The constituent can be seen easily \'Homo\' means the same \'Hetero\' means different E.g. sugar solution, soft drinks, salt solution, Milk,soil, sand and water, oil and water 1. Classify each of the following as a mixture or a pure substance. 2. Define and give four examples illustrating each of the following terms. 2. A. Salt. B. Metalloid C. Metal D. Non-metal 3. B. benzene B. oil C. sugar D. sulfur 4. C. air B. Sea water C. Pure water D. Brass ### 2.4. Change around Us: Physical and Chemical Changes +-----------------------------------------------------------------------+ | *After completing this section, you will be able to* Describe | | physical and chemical change. | | | | - Distinguish the physical and chemical changes using their | | characteristic. | | | | - Conduct some simple activities to show physical and chemical | | changes and write group report. | | | | - Observe and describe physical and chemical changes that are | | important in everyday life. | | | | - Identify useful and harmful physical and chemical changes. | +-----------------------------------------------------------------------+ ###### 2.4.1. Physical Change ###### 2.4.2. Chemical Change +-----------------------------------------------------------------------+ | **Experiment 2.3 Title:** Rusting of iron. | | | | **Objective**: To investigate the type of change that occurs during | | rusting of iron | | | | **Materials and Chemicals:** test tube rack, iron nail, test tube | | **Procedure:** | | | | 1. Put a few lean shiny iron nails into a test tube containing some | | fresh tap water. The water contains dissolved air. | | | | 2. Set the test tube in a rack. After a few days observe the change | | that has taken place. | | | | Figure: 2.15 rusting of iron | +-----------------------------------------------------------------------+ 1. What color do you observe on the iron nail? 2. Is the change physical or chemical? Why? ###### 2.4.3 Characterstics of physical and chemical changes 1. List the characteristics of physical and chemical changes you know. 2. Compare and contrast the characteristics of physical and chemical changes. - The composition of substance is not altered. - It is easily reversed by physical means. - Energy changes are not necessarily. - It is a change in physical property. - New substances with new properties are formed - The composition of substance altered - It is accompanied by Energy changes - The change is not easily reversed - It is a change in chemical property ###### 2.4.4 Useful and Harmful physical and Chemical Changes **Activity 2.15** a. Important physical changes b. Important chemical changes c. Harmful physical changes d. Harmful chemical changes ##### Useful effect of Physical changes - Evaporation and condensation create water cycle - Freezing preserves food, medicine, and other materials - Melting, cutting, bending and mould different tools and accessories - To get substances in the form, shape or size we want - To mix two or more substances together - To separate substances from their mixtures ##### Harmful effect of Physical changes ##### Useful effect of chemical changes ##### Harmful effect of Chemical changes a. the cutting of wood b. interaction of food with saliva and digestive enzymes c. The vigorous reaction of potassium metal with water to produce hydrogen gas and potassium hydroxide. d. Straightening a bent piece of iron with a hammer. e. The ignition and burning of a match. f. photosynthesis g. boiling of an egg. h. boiling of water i. dissolution of salt 1. Change in size, shape and state of a substance is a\_\_\_\_ A. chemical change B. physical change 2. Which of the following statements is correct? B. Evaporation is a chemical change C. Digestion of food is a chemical change D. Burning of paper is physical change E. all 3. Among the following which one is a physical change? F. Burning of magnesium ribbon B. Fermentation C. Making an iron bar magnetic D. all ### 2.5. Separation of Mixtures and its Application +-----------------------------------------------------------------------+ | *After completing this section, you will be able to* List methods | | of separation of mixtures. | | | | - Give some specific examples of mixtures that can be separated by | | filtration, decantation, simple distillation, magnetic separation | | and using separator funnel. | | | | - Name apparatuses used in decantation, filtration, simple | | distillation, using separator funnel. | +-----------------------------------------------------------------------+ - Assemble apparatuses used in decantation, filtration, simple distillation, separator funnel. - Conduct and report on an investigation that uses physical means such as particle size, density, boiling point, solubility and magnetism to separation. - Perform simple activities in group, to carry out the separation of mixtures using local materials and write a group report. Compare and evaluate the different ways of separating mixtures from products in community. +-----------------------------------------------------------------------+ | **Activity 2.16** | | | | Discuss the following questions in groups and present your conclusion | | to the class | | | | 1\. Write the common separation methods for the following | | | | common mixtures from your daily life experiences | | | | A. A mixture of Teff and peas | | | | B. A mixture of iron filings and sulfur powder | | | | C. A mixture of chalk particles in water | | | | D. A mixture of cooking oil and water | | | | E. Salt solution | | | | F. A mixture of alcohol and water | | | | G. A mixture of salt and sand | | | | H. A mixture of orange, banana and mango | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ ###### 2.5.1. Separation Techniques of Mixture a b 1. Mix the sand with the iron fillings in the plastic plate. 2. Wrap the plastic bag around the bar magnet  just the upper layer in thefunnel. ^Figure\ 2.20:\ Separation\ of^ immiscible liquids using separating Collect this liquid into ~funnel~ ##### Iv. Evaporation +-----------------------------------------------------------------------+ | **Activity 2.17** | | | | Perform the following activity. Dissolve sodium chloride (or any | | other soluble salt) and water to form a homogeneous mixture | | (solution). | | | | How can you recover the salt again? | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ Figure 2.22: Evaporation of a solution +-----------------------------------------------------------------------+ | **Activity 2.18** | | | | Perform the following tasks in groups and present your conclusion to | | the class. The following mixtures can be separated using a | | combination of separation techniques. Mention all the possible | | separation techniques. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ +-----------------------------------------------------------------------+ | **Activity 2.19** | | | | Perform the following tasks by asking your parents/guardians/ | | grandparents/elders in the neighborhood on the separation techniques | | used in daily lives. Prepare a table of such activities of daily life | | in which sedimentation, decantation, filtration and evaporation are | | used/ occurs. Then present your findings to the whole class. | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ +-----------------------+-----------------------+-----------------------+ | No. | Physical process | Application | +=======================+=======================+=======================+ | | Filtration | - River water is | | | | potable | | | | | | | | - Separation of | | | | honey from its | | | | comb | +-----------------------+-----------------------+-----------------------+ | | Evaporation |  Common salt is | | | | obtained from sea | | | | water on large scale. | +-----------------------+-----------------------+-----------------------+ | | Distillation |  Alcoholic beverage | | | | such as whisky, gin, | | | | brandy, areki are | | | | manufactured | +-----------------------+-----------------------+-----------------------+ | | Magnetic separation |  To separate iron | | | | and steel from non | | | | magnetic objects such | | | | as, glass, plastic, | | | | aluminum, etc. | +-----------------------+-----------------------+-----------------------+ | | Sedimentation |  Drink homemade | | | followed by | coffee, tella | | | decantation | | +-----------------------+-----------------------+-----------------------+ Matter Magnetic Separation Physical Changes Particle Theory Decantation Compounds Diffusion Pure Substance Elements Chemical Property Non Metal Evaporation Sublimation Density Freezing Boiling Point Freezing Point - Matter is anything that has mass and occupies space. It can exist in three states: solid, liquid, and gas. - The idea that matter is made up of tiny particles is called the Particulate nature of matter. - Particle theory of matter tell us the particles of matter are always moving. - Diffusion is the mixing and spreading out of a substance with another substance due to the movement or motion of its particles. The three states of matter (solids, liquids and gases) can be interconverted without changing the composition of the substance. To change a substance from one state to another, energy must be added or removed. Melting, freezing, evaporation, and condensation are all changes of state. - A physical property can be measured and observed without changing the composition or identity of a substance. - A chemical property is a characteristic of a substance thatdescribes the way the substance undergoes or resists change to form a newsubstance. - Matter can be classified in terms of its chemical composition into two broad categories: pure substances and mixtures pure substances. - A pure substance is a single kind of matter that cannot be separated into other kinds of matter by any physical means. - Pure substances are classified as elements and compounds. - An element is a pure substance that cannot be broken down into simpler substances by ordinary chemical means. - A compound is a pure substance composed of two or more elements that are combined chemically in a definite proportion by mass. A mixture is a physical combination of two or more pure substances in which each substance retains its own properties. A homogeneous mixture (also known as solution) has a uniform composition and properties throughout. - Heterogeneous mixture is a mixture that does not have a uniform composition throughout. - Changes are classified as either physical or chemical changes. - A physical change is a process in which a substance changes its physical appearance but not its chemical composition. - A chemical change is a process in which a substance undergoes a change in chemical composition. - Mixtures can be separated using a variety of techniques. The process of separating the constituent substances of a mixture by physical methods, taking advantage of the differences in their physical properties is called separation process. - Some of the methods used to separate mixtures are Separation by hand, Sieving Filtration, evaporation, magnetic separation, decantation and distillation Review Exercise --------------- 1. Depending upon the temperature, water can exist in solid, liquid or gas states. 2. A gas has neither a definite volume nor a definite shape. 3. Dust, smoke, bacteria, air born viral particles are components of particulate matter. 4. Elements can be further decomposed by ordinary chemical means. 5. Heterogeneous mixture contains one phase. 1. All of the followings are matter except 2. Which of the following decrease during the phase (state) changes of A. B. C. D. 3. Which of the following is not the property of solids A. Solids have little tendency to diffuse B. Solids are extremely difficult to compress C. Solids are fluids D. Solids have definite volume and definite shapes 4. The particular physical state of substance depends on 5. Which of the following has no definite shape and volume? 6. The interaction of substance with light results 7. Which of the following is not a physical change? A. B. 8. All of the following are heterogeneous mixtures except 9. Which of the following is not a metal 10. Which of the following has variable composition? 11. A mixture of sand and sugar can be separated by A. evaporation followed by distillation B. filtration followed by evaporation C. dissolution followed by filtration and evaporation D. dissolution followed by evaporation and filtration. 12. The conversion of a vapor directly to solid without passing through a liquid state is called\_\_\_\_\_\_\_\_\_\_\_ 13. Distillation is used in the process of preparation of 14. Identify the heterogeneous mixture among the following 15. Grade 7 students in a certain school were given the task of separating, iron fillings, sand and salt. Which of the following process is the most appropriate order? B. C. 16. I. Physical changes are easily reversible. 17. Which two state of matter are fluids? A. Solid and liquid C. Liquid and gas