evidence of chemical changes how can you tell something has changed into something new?
TRANSCRIPT
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Evidence of Chemical ChangesHow can you tell something has changed into something new?
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Evidence we already know:• A gas is produced
▫Evidence: you will see bubbles or hear fizzing
• The temperature changed▫What you are working with got hot or cold
Endothermic = feels colder Exothermic = feels hotter
• Color change▫Think of the Statue of Liberty – it WAS copper,
now it’s a green color….that’s a chemical change!
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More evidence!
•It smells different▫If something has a different odor than
before, a chemical change has happened•It changes form
▫If you burn something, like paper•Light, heat, or sound is given off
▫When something explodes•If a solid forms
▫Science Fancy Word: solid forms = precipitate
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If we could see the atoms…
Which part of the atom is responsible for reactivity?Hint: it’s the outermost something…
Those interact with each other to
form something new. The Main Point!
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So what is a physical change?
Physical Change: you do not make a new substance
Physical Change examples:▫Changes states of matter (solid, liquid, gas)
Example: Water, Ice, and Steam are all the same – you have just changed the physical properties
Example: making a baseball bat out of wood – the wood has only changed shape
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Let’s get some practice!
In the next few slides, use your ring cards to select either:
A) Physical ChangeB) Chemical ChangeC) Don’t Know
Be prepared to explain why it’s the type of change it is! You can use your notes from today if you need to.
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Which type of change?
http://whatscookingamerica.net/Foto4/BoilingWater.bmp
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Which type of change?
http://www.google.com/imgres?q=ripping+paper&hl=en&gbv=2&tbm=isch&tbnid=thafyuekIpHt6M:&imgrefurl=http://www.bairarteditions.com/ripper/&docid=0Yf_4cf2jAxknM&w=576&h=317&ei=pblyTvWRM5TJsQL46pDaCQ&zoom=1&iact=hc&vpx=675&vpy=190&dur=889&hovh=166&hovw=303&tx=211&ty=69&page=1&tbnh=94&tbnw=171&start=0&ndsp=15&ved=1t:429,r:4,s:0&biw=1024&bih=630
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Which type of change?
Digesting Food
http://www.google.com/imgres?q=digesting+food&hl=en&gbv=2&tbm=isch&tbnid=3w1uFRwVZsXKyM:&imgrefurl=http://byhealth.com/digestive-system&docid=EsLSOzq6M__IvM&w=699&h=837&ei=-7lyTtvvCO7LsQK-0bCZCw&zoom=1&biw=1024&bih=630&iact=rc&dur=265&page=1&tbnh=109&tbnw=91&start=0&ndsp=17&ved=1t:429,r:4,s:0&tx=69&ty=39
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Which type of change?
Flammability
http://www.google.com/imgres?q=flammability&hl=en&gbv=2&tbm=isch&tbnid=REMWMZsxrWRlJM:&imgrefurl=http://www.sgs-cqe.de/en/flammability-test-for-plastic-materials-/-components.html&docid=ZGVnk1mVtYju6M&w=275&h=199&ei=srpyTqWoBcKAsgLPspi_CQ&zoom=1&iact=hc&vpx=468&vpy=131&dur=1856&hovh=159&hovw=220&tx=133&ty=102&page=1&tbnh=123&tbnw=162&start=0&ndsp=15&ved=1t:429,r:7,s:0&biw=1024&bih=630
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Which type of change?
http://custom.buyitsellit.com/29169/images/staedlter/pencils/158_sharpening.jpg