professor Dave here let's talk about types that matter
matter is anything that has mass
and occupies space. it can have many forms. we will commonly divide matter into
three phases
solid liquid and gas. we are probably familiar with these terms
let's define them anyway. a solid has fixed
shape and volume, the particles are touching and do not move
a liquid has fixed volume but no fixed shape
it will mold to its container. the particles are still touching
but they do move fluidly. a gas has no fixed volume
or fixed shape. it will completely fill its container. the particles are far apart
moving freely, and seldom touch. matter will frequently change forms
and describing these changes is at the heart of chemistry. a physical change
is one in which the chemical composition of the substance is
unchanged. when ice melts water is going from the solid phase
to the liquid phase. the way the water molecules are arranged
changes but they are still water molecules. a chemical change
is one in which the chemical composition of the substance does change
chemical bonds between atoms must break and form
to generate completely new substances. here
hydrogen gas and oxygen gas combine to form water
notice that hydrogen and oxygen used to be connected to themselves
and are now connected to each other. new bonds
new substance, chemistry has occurred
so things like a substance changing from one phase to another
are always physical changes. but if we make an entirely new substance with new
chemical bonds
thats a chemical change. a pure substance
is one that can't be separated into other materials
by any physical process. water whether you boil
or freeze it will still be water. it's a type of molecule
which is just multiple connected atoms. an element can't be broken down into
smaller parts by physical
or chemical means. for example water is not an element
it's a compound because it is made up two or more
elements, in this case oxygen and hydrogen. by a chemical process we can
divide water into these two elements
but that's as far as we can go with chemistry. these are now molecules
of a given element. a mixture is made of two or more
pure substances and these can be separated by physical processes
if you boil salt water the water will evaporate
and the salt won't so the substances will have separated
a mixture can be homogeneous meaning all the substances
are distributed evenly and every section looks the same
like sugar and water, or they can be heterogeneous
meaning they are not distributed evenly and zooming in on different sections
would look differently like oil and water.
we've got pure substances which can be elements made of only one type of atom
or compounds which are made of different types of atoms
but are still just one type of molecule.
or we can have mixtures which are made of multiple types of molecules
and are arranged in either homogeneous or heterogeneous fashion. let's check
comprehension
thanks for watching guys. subscribe to my channel for more tutorials
and as always feel free to email me