Watch this video on physical and chemical changes
Which is NOT a physical change?
Which of the following could indicate a chemical change is happening?
What is a common example of a physical change?
Which best describes a chemical change?
He mentioned that chemical changes can always be expressed with a chemical formula. For instance baking soda and vinegar reaction is shows with this formula.
Do the molecules on the left look exactly the same as the molecules on the right?
Sometimes physical changes will also be shown with a chemical equation - but you can always tell when an equation shows a physical change. for instance
the subscript (s) stands for solid. it tells you the molecules are in a solid state
the subscript (l) stands for liquid
What do you think this equation is showing
the chemical formulas don't change, but the state of the matter changes is a physical change
The following is an equation for sugar dissolving in water
(aq) stands for aqueous, from the latin word aqua, which means water. Aqueous tells you that something is dissolved in water. You don't have
did the molecule for sugar change from the left side to the right side?
Is sugar dissolving in water a chemical or physical change?
watch the following video on the difference between dissolving sugar and salt
do you have any questions?
8th and honors students keep going, 6 and 7th non-honors, you may be done,
we define a physical change as a change that doesn't change the substance, and a chemical change where the substance before is different as the substance after. the chemical formula for salt dissolving is
this looks like the molecule has changed, but this is still considered a physical change. why?
What happens when you rub a balloon against your hair
Atoms like Na and Cl have something in common - they are both very close to having the same set of electrons as a noble gas. one has one too many electrons (Na) and the other is one shy (Cl) when they get close, the Na gives the Cl the extra electron it wants, and now both don't need to interact with other atoms, just the way noble gasses don't need to interact. However they are charged now, and they are oppositely charged, so this means
If you were to explain to a student why salt dissolving is still considered a physical change and not a chemical change, how would you explain that?
Would it bother you to know that some scientists do consider salt dissolving in water a chemical change? and there isn't scientific agreement on it?