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.
