Evidence of Chemical ChangesHow can you tell something has changed into something new?

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!

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

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!

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

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.

Which type of change?

http://whatscookingamerica.net/Foto4/BoilingWater.bmp

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

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

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

Which type of change?

http://custom.buyitsellit.com/29169/images/staedlter/pencils/158_sharpening.jpg