Science yr8 Term 4 part 3
what is a physical change?
The shape, size or form of the object is changed but no new substance is produced. Can involve changes in the states of matter. Easily reversible
what is a chemical change?
Atoms with 2 or more substances are rearranged to form new substance
What are the signs of chemical changes
Gas is produced (bubbles), permenant colour change, solid is formed, heat/light/sound/electricty is produced
What is a reactant and product?
Reactants – the substance(s) you start with in a reaction
Products – the substance(s) produced in the reaction.
How does tempreture affect reaction rates?
Tempreture sppeds/slows raction rates. Adding heat adds energy to the particles which makes them move faster and therefore they collide more often
how does surface area affect reaction rates?
Is the amount of area exposed on a surface of a molecule that allows for reactions to occur. Greater surface area will also result in an increase in reaction rate.
How does concentration affect reaction rates?
Concentration is the amount of substance in a defined space.
Higher concentration increases reaction rate. Increased concentration means that there are more particles per volume, therefore collisions happen more readily
How does a catalyst affect reaction rates?
Are substances that speed up chemical reactions, without being used up themselves