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Copy of Physical & Chemical Change
derek mcdowallon 31 December 2012
Transcript of Copy of Physical & Chemical Change
change? Physical change Equations ...when a substance changes, but no new substance is formed.
May be grouped into 3 types:
1. Change of shape
2. Change of size
3. Change of state Physical & Chemical change During a physical change, are there any... 1. New substances produced?
2. Changes in chemical bonds between the particles?
3. Change in properties of the substance? Chemical change ...when a substance changes into another substance OR substances combine to form one or more new substances. During a chemical change, are there any... 1. New substances produced?
2. Changes in chemical bonds between the particles?
3. Change in properties of the substance? Hint... when we burnt paper, was it still 'paper?' During a physical change, the chemical make-up is NOT changed. During a chemical change, the particles in the original substances rearrange and bond DIFFERENTLY to form one or more new substances, with different characteristics. Word equations Chemical equations Corrosion
Experiment These tell us if a chemical reaction has taken place! Light production
Change in colour
Change in odour (scent)
Precipitation (solid produced out of a solution)
Change in temperature Year 8 Review Extending our knowledge from Year 8... Phase changes Solids Gases Liquids Separation States Solutions Solution: mixture made of 2 components mixed evenly.
Solvent: dissolves the solute
Solute: substance dissolved IN another substance (the solvent). Filtration
Sublimation Quizzzzzz Q1. Which is an example of physical change? Q9. Which is not a clue that could indicate a chemical change? Q10. What property stays the same during physical and chemical change? A. Mixing baking soda and vinegar together, producing bubbles and foam
B. A glass cup falls from the counter and shatters on the ground
C Lighting a piece of paper on fire, and the paper burns and leaves ashes.
D. Baking a birthday cake for your mother Q2. Which is an example of chemical change? A. Filling up a balloon with hot air.
B. Taking a glass of water and freezing it by placing it in the freezer.
C. A plan collecting sunlight and turning it into food.
D. Your dog ripping up your homework. Q3. Which change can easily be reversed? A. Chemical change
B. Physical change
C. Both a physical and chemical change
D. Neither a physical or chemical change Q4 When a new substance is formed with different properties than the original substance, it is called... A. A chemical change
B. A physical change
D. Boiling A. a chemical change.
B. a physical change.
C. both a physical and chemical change.
D. neither a physical or chemical change Q5 If the chemical properties of a substance remains unchanged, and the appearance or shape of a substances changes it is... Q6. Which is an example of a physical change? A. Metal rusting
B. Silver tarnishing
C. Water boiling
D. Paper burning Q7. What characteristic best describes what happens during a physical change? A. Composition changes
B. Composition stays the same
C. Form stays the same
D. Mass is lost Q8. Which is an example of chemical change? A. Water freezes.
B. Wood is cut.
C. Bread is baked.
D. Wire is bent. A. Change in colour
B. Change in shape
C. Change in heat energy
D. Change in odour A. Density
D. Arrangement of particles Exothermic
Reactions An example of a chemical reaction... Endothermic
Reactions In exothermic reactions, energy (usually heat) is PRODUCED- this WARMS the environment. http://www.middleschoolchemistry.com/multimedia/chapter6/lesson7 In endothermic reactions, energy (usually heat) is ABSORBED- this COOLS the environment. Methane gas exposed to oxygen
carbon dioxide and water Methane (g) + oxygen (g) carbon dioxide (g) + water (g) CH (g) + 2O (g) CO (g) + 2H O (g) REACTANTS PRODUCTS REACTANTS PRODUCTS Combustion of methane animation:
C:\Users\Cassie\Documents\Placement\Williamstown Placement\Yr 8JO\Physical & Chemical change\Animations\combustion_of_methane.swf 4 2 2 2 - REACTANTS: the substances present at the beginning of a chemical reaction.
Located on the left hand side of the equation
- PRODUCTS: the new substances that are produced in the chemical reaction.
Located on the right hand side of the equation.
- A right-pointing arrow is used to point to the products of a reaction •Sometimes, scientists will simplify word equations by using chemical symbols to make a chemical equation.
•The chemical symbol for each element can be found by looking at the periodic table.
•States of matter are usually identified in the chemical formula:
- Solid (s)
- Liquid (l)
- Gas (g Iron and steel rust when they come into contact with water and oxygen. Both water and oxygen are needed for rusting to occur. In the experiment below, the nail does not rust when air or water is not present. Remember that 21 per cent of the air is oxygen. Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust. This is the word equation for the reaction:
iron + water + oxygen ---> hydrated iron(III) oxide
Salt dissolved in water does not cause rusting, but it does speed it up, as does acid rain.