Chemistry is the study of matter, its properties and its changes or transformations. Feb 19 11:08 AM

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1 What is Chemistry? Chemistry is the study of matter, its properties and its changes or transformations. Matter is anything that has mass and takes up space. All matter has physical and chemical properties. Physical properties are the characteristics of a substance. Examples are colour, texture, odour, luster, hardness, malleability, ductility, melting point, boiling point, solubility, viscosity, density A physical change involves a change of state. The matter itself doesn t change, just its form (solid, liquid or gas). Most physical changes are easy to reverse. Untitled 1

2 A chemical property is a characteristic behaviour that occurs when a substance changes to a new substance. A chemical change is generally very difficult to reverse. When a chemical change occurs it is called a chemical reaction. The reactants (original substances) react together to form products (new substances that were not present originally). Examples: Combustibility - Ability of a substance to react with oxygen to produce CO 2, water and energy. Reaction of a metal with Acid the metal reacts with the acid to form hydrogen gas and a soluble salt. Physical and Chemical Properties Chemistry is the study of maer. Maer is anything that has mass, and takes up space. How do you know a chemical is a CHEMICAL in Science? By its... properes There are two types of properes: physical and chemical. PHYSICAL properes are used to describe or explain the object. These characteriscs are descripons. 2

3 Property Description Example Hardness Odour Malleability Ductility Melting Point Boiling point Solubility Viscosity Density Colour Brittleness Measure of resistance of solid to being scratched/dented Diamonds very hard Chalk very soft Apples sweet The smell Oxygen gas odourless Playdough is Ability to be malleable. hammered into a sheet A boulder is not Ability to be pulled An elastic is ductile, a into a wire paper is not Temp. at which it Ice melts at 0 melts Temp. At which it Water boils at 100 boils Sugar dissolves in Ability to dissolve water How a substance Honey is very viscous flows (flows slowly) Oil is less dense than Ratio of mass to waterwater has a volume density of 1g/cm3 Is it black, white, red, Banana is yellow etc. Does it break when bent State Solid liquid or gas At 30 Uncooked spaghetti is brittle. Cooked spaghetti is not brittle chemical properes describes how a substance will react or combine with another substance. Examples Include: 1. Combusbility (will it burn?) 2. Reacts with AIR /O 2 3. Reacts with Water /Acid 3

4 Feb 14 9:16 PM Place a P (for physical property) or C (for chemical property) beside each of the following statements: 1. The sulfur was yellow 2. The corn syrup flows slowly 3. The magnesium burned 4. The metal felt smooth 5. The mercury transmied the electricity 6. Water freezes at 0⁰C 7. A nail sinks in water 8. Iron rusts in air 9. The sulfur breaks easily 10. Sodium explodes in water 4

5 Types of changes in Chemistry In a physical change the substance involved remains the same. «Changes of state and size are physical changes. «dissolving is also a physical change. In a chemical change the original substance is changed into one or more different substances that have different properties «chemical changes always involve the production of new substances «most chemical changes are difficult to reverse Burning, cooking, and rusting are all examples How can you tell if a chemical change has occurred? The following suggest that a new substance has been produced. 1. Colour Change 2. Gas produced (bubbles) 3. Heat released or absorbed 4. Light released 5. Odour change 6. Precipitate forms from 2 liquids 5

6 Pracce Quesons: 1. Which one of the following is an example of a physical change? a. Iron rusng b. A steak cooking c. Sugar dissolving in water d. A candle burning Feb 19 11:29 AM 2. A physical change means that no new substance is formed A. True B. False Feb 19 11:29 AM 6

7 3. Breaking water up by separang it into hydrogen and oxygen is an example of a... A. Physical B. Chemical Feb 19 11:29 AM 4. Melng and boiling causes a... A. Physical change B. Chemical change Feb 19 11:29 AM 7

8 5. A change in size or shape is a... A. Physical change B. Chemical change Feb 19 11:30 AM 6. A chemical change means that a new substance with new properes is formed. A. True B. False Feb 19 11:30 AM 8

9 7. The fact that sugar is white is a A. Physical property B. Chemical Property Feb 19 11:30 AM 8. Iron rusts when exposed to air. This is a A. Physical property B. Chemical Property Feb 19 11:30 AM 9

10 9. Which one is not a physical property of hydrogen? A. It is a gas B. It is explosive C. It is colourless Feb 19 11:30 AM 10. Which one of the following is not a physical change? A. Clothes drying in the dryer B. Making a cup of coffee C. Chopping Wood D. Boiling an egg Feb 19 11:25 AM 10

11 Chemical and Physical Changes Pracce For each of the following determine if it is a Chemical or a Physical change. Give a specific reason for your choice. 1. A hot dog is cooked. Physical or Chemical (circle) Explain: 2. Thousand Island dressing is mixed with Mayonnaise to make a special sauce. Physical or Chemical (circle) Explain: 3. Water is boiled in preparaon for making pasta. Physical or Chemical (circle) Explain: 4. Old hamburger goes bad in the fridge. Physical or Chemical (circle) Explain: 5. You get a taoo. Physical or Chemical (circle) Explain:. Feb 19 11:27 AM Change ice melts sulfur is burned glass breaks a match is struck mercury is heated to produce mercury vapour wax hardens on a candle silver tarnishes leaves change colour and fall nail polish remover evaporates a dish rag dries wood is hammered together to build a playhouse sugar dissolves in tea vinegar is added to baking soda muddy water is allowed to settle an egg is fried butter is melted for popcorn sand is separated from gravel lemonade powder is mixed in water the lawn is mowed metal rusts hair is bleached fireworks explode oranges are squeezed to make orange juice leaves change colour and fall Physical or Chemical? Clue Feb 19 11:27 AM 11

12 000_Chemical and Physical Properties.notebook Jan 28 10:04 AM Jan 28 10:22 AM 12

13 Bill Nye the Science Guy Chemical Reactions 1. When do chemical reactions occur? when electrons hook together 2. Why did the steel wool react so much better in the plastic container full of oxygen? there was more oxygen available to keep the reaction going 3. Why did the carbon dioxide fire extinguisher put out the tornado of fire? the carbon dioxide replaces the air around the fire so there is no more oxygen for it to keep burning (reacting) 4. What gas is produced when you mix baking soda and vinegar together? carbon dioxide is produced (CO 2 ) 5. What is the chemical formula for water? H 2 O Feb 3 7:46 PM 6. What two pieces of information does this formula give us? the types of atoms (elements) in a water molecule the number of each atom (element) in the water molecule 7. What would happen if you were to breath chlorine gas? you would be killed 8. What happens when sodium is put in water? bubbles and turns on fire and then explodes 9. What is formed when sodium and chlorine react together? table salt (sodium chloride NaCl) Feb 3 7:56 PM 13

14 10. What is the name given to people who work with fireworks? pyrotechnician 11.How do fireworks get their different colours? different metals are used 12. What else besides carbon dioxide is also created when vinegar and baking soda are mixed together? heat 13. How many natural elements are there? What chemical did Alfred Nobel discover? dynamite (TNT trinitro toluene) Feb 3 8:22 PM 15. What award has been named after Alfred Nobel? the Nobel Prize (for peace, for art, and for different sciences) winner is given $1 million 16. How does a cold pack work? it it has 2 chemicals in it when the barrier inside the pack is broken the two chemicals react together the reaction takes up more heat than it gives off and so feels cold 17. How are elements grouped together on the Periodic Table? they are grouped by similar chemical reactions Feb 3 8:23 PM 14

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