Acids and bases Acids and bases and be very useful , but can also be very dangerous It is very important to always read the chemical labels when dealing with acids and bases

How do we tell? How do we tell if a substance is an acid or a base? Use an indicator such as litmus paper, red cabbage juice, grape juice, etc... Indicators react in the presence of acidic or basic substances.

Litmus paper Acid substance : Red litmus -> stays red Blue litmus -> turns red Basic substance : Red litmus -> turns blue Blue litmus -> stays blue Neutral substance: Red litmus -> stays red

pH scale This scale classifies substance according to their acidity or alkalinity The scale ranges from 0 -14 Acid <7 Base >7 Neutral =7

Change of State & Particle Theory Solid (close particles) +heat *melting point = liquid (particles are farther apart) + heat *boiling point = gas (particles far apart)

Physical vs. Chemical transformation In a physical change you only change the state of the substance. In a chemical change your substance changes its chemical properties and becomes something new Signs of a chemical change: 1) gas is formed 2) A residue is formed 3) heat or light is produced 4) A colour change occurs

Rule of thumb on physical vs. Chemical changes If it can go back to its original form  physical change If it can’t revert to its original form  chemical change

Law of conservation of mass ***The mass substances that undergo a transformation is always equal to the mass of the resulting substances

In class work P.193 (# 9-12) P.196 (# 1-4) P. 197(# 1-3) List whether the following are physical/chemical changes. Lake freezing Crushing an ice cube Burning toast Melting a gold bar Cutting a loaf of bread A tree decomposing