5 th Grade GA Science Physical and Chemical Changes Topic Overview

hey scientists let's talk about changes have you ever noticed that sometimes when you change things you can change it back but other times you can't and it's stuck like that forever this morning decided to make myself some breakfast before leaving the house got out of frozen smoothie from the freezer and set it on the counter to melt and then got on piece of bread and put it in the toaster right as was about to eat realized was late and did not have time to eat anymore threw my smoothie back into the freezer but couldn't figure out how to undo toasting my bread to put it back up that's because you can't sometimes when you make change it's permanent why is that well let's take look there are two different types of changes physical and chemical changes physical changes are what happens when something's appearance changes but the composition stays the same while chemical changes are when something's composition changes and something new is made know know you're probably like okay but what does that mean well the easiest way to think about it is to ask yourself two questions can undo this and was something completely new made when you look at physical change they can all be reversed or undone when you look at chemical change something new is always made and it cannot be reversed or undone let's take look at some physical changes first let's focus on changing states of matter say you have liquid it could be water but that's kind of boring want to talk about soda we all know from previous lessons and experiences that this liquid deliciousness can be frozen nothing is as tasty as eating frozen soda on hot summer day we also know that if you leave that frozen soda out too long it just melts and goes back to its original state that's how all states of matter are solids liquids and gases are really easy to change back and forth all you have to do is change the temperature so if you have liquid boiling and turning into water vapor ask yourself can undo this yes if you put cold bowl over the boiling water to catch the steam the vapor will decrease in temperature and change states back to liquid water other physical changes include both mixtures and solutions let's make mixture of iron filings and sand can undo this yes really easily in fact all have to do is pass magnet over my mixture and it pulls out all of the iron filings for me so this is physical change if zoom into my molecules and atoms can see that even though mix the sand and iron they're still the same on molecular level and haven't changed in composition what about solutions well let's take some water and add some pop and pink lemonade when look at the solution on the counter can see that the lemonade is the same color as the lemonade powder and it didn't change colors it didn't make something new if looked at the molecules would see that the water and the lemonade haven't changed composition but can it be undone yep all have to do is boil the water long enough and will evaporate and leave the pop and pink lemonade powder in the bottom let's take look at chemical changes remember won't be able to undo any chemical changes and whatever we're looking at will undergo change in composition meaning something new will be made this could be change in color releasing smoke or making new compound the easiest example of chemical change is burning burning anything will always always result in chemical change let's burn some matches the matches release smoke which is brand new substance but can we undo this change nope almost all baking falls under chemical changes as well from baking chicken to cookies and from pies to potatoes let's take look at those cookies to make cookies first you add sugar flour water eggs butter and chocolate chips into sticky mixture remember up to this point is just physical change because could undo this but something happens when put that yummy cookie dough into the oven let's take closer look at the molecules my sucrose or sugar is changing into caramel and when that happens the heat is breaking down the bonds in the sucrose forming two new sugar molecules glucose and fructose the same thing happens in the proteins in the eggs and butter as bake as well if were to bite into the cookie once they come out of the oven i'd be able to tell that they tasted different and that they've changed color this is chemical change any type of chemical reaction is also chemical change if you've ever made elephant toothpaste in lab well it's not really toothpaste but it's chemical reaction that creates colored foam heat it's another example of chemical change as we look at some new questions let's remember our two big questions that will help us decide whether something's chemical or physical change can the change be undone and did the change make something new