Transcript Chemical Reactions Mr. Campbell

Chemical Reactions
Ms. Mudd
8th Grade Chemistry
Chemical Reactions
Objectives
► State how matter and changes in matter
can be described
► Explain how you can tell a chemical reaction
occurs.
Chemical Reactions
► What
is matter?
► Anything that has mass and takes up space
► What is chemistry?
► Study of matter and how it changes
Chemical Reactions
Matter has 2 major properties
► 1.) Physical property- characteristic of a
substance that can be observed without changing
it into another substance.
► What are some examples of physical properties?
► Temperature, Color, Texture, Flexibility
► Physical Change- any change that alters the
form or appearance of a substance but doesn’t
change it into another substance.
Chemical Reactions
► 2.)
Chemical Property- characteristic of a
substance that describes its ability to
change into another substance
► What are examples of chemical properties?
► Burning, Tarnishing, Rusting
► Chemical Change- A change in matter
that produces one or more new substances
► Occurs when bonds break and new bonds
form.
Chemical Reactions
Physical Change or Chemical Change?
► Ice melting?
► Physical
► Burning Magnesium causes it to combine with oxygen in
the air, forming Magnesium oxide
► Chemical
► Flattening a marshmallow?
► Physical
► Roasting a marshmallow?
► Chemical
► Water left in a cup disappearing over time?
► Physical
Chemical Reactions
Two observable changes of chemical reactions
1. Changes in properties
► Color Change
► A solid may appear when 2 substances are
mixed (Precipitate)
► A gas may form from a liquid or solid
(bubbles may form)
Chemical Reactions
► When
water is boiled and bubbles form, is it a
chemical change?
► No
► Electrolysis of water produces H2 gas and O2
gas. Is this a chemical change?
► Yes
► Color change in leaves because chlorophyll is
being produced. Is this a chemical change?
► Yes
Chemical Reactions
2. Changes in Energy
► What are some types of energy?
► Heat, Light, Electricity
► As matter changes, it can release or absorb
energy
► This is usually observed by temperature
Chemical Reactions
Endothermic Reaction
► Endo= In
Thermic= Heat
► Reaction in which energy is absorbed
► When frying an egg, energy is being
absorbed causing the egg whites to go from
a liquid to solid form
Chemical Reactions
Exothermic Reaction
► Exo= out
Thermic= Heat
► Reaction in which energy is released
(usually as heat)
► In an airplane, Fuel and oxygen react
releasing energy in the form of heat
► The expansion and movement of the gases
out of the plane exerts enough force to
shoot the plane forward.