Physical change: a change in which no new substances are formed. the form of the substance is changed but not it's chemical composition (ice melting, bread toasting)
chemical change: any change that results in the formation of new chemical substances. this type of change modifies molecules and atoms by making and breaking the bonds between atoms! (iron rusting, gas burning)
so basically a physical change just changes the appearance of a substance, but a chemical change changes the makeup on a molecular level. i hope this helps you out!
As the earth is in the form of a sphere, the angle of incidence of the sun's rays at the earth's surface increases from the equator towards the poles and therefore the amount of heat received on a GIVEN AREA diminishes in the same direction. Temperature is therefore normally hottest near the equator and coolest near the poles.
If the reaction is a chemical change, new substances with different properties and identities are formed. This may be indicated by the production of an odor, a change in color or energy, or the formation of a solid.
In a movable pulley system, where does the other effort come from? is carried by this end of the rope. This means that the structure (ceiling) does half the effort.
