Download Unit 3 - Section 5 Summary

Grade 9 Academic Science
Chapter 5 Chemistry – What I Know
Matter
Anything that has mass and volume.
 Volume is the amount of space that an object takes up.
 Mass is The amount of matter an object contains
Pure Substance -- A substance that contains only one type of particle
 Element -- A pure substance composed of particles that cannot be broken down
into simpler particles (e.g., oxygen, hydrogen)
 Compound -- A pure substance that contains two or more different elements in
a fixed proportion (e.g., carbon dioxide (CO2), water (H2O))
Mixture
 Solution (Homogeneous)
 Mechanical Mixture (Heterogeneous)
Particle Theory of Matter
1. All matter is made up of tiny particles (i.e., atoms, molecules) that have empty
spaces between them.
2. Different substances are made up of different kinds of particles. In another
way, a PURE SUBSTANCE is composed of its own kind of particles which are
different from the particles of other pure substances (e.g., gold is made of only
one kind of particle).
3. Particles are in constant motion...regardless of state. That is, all particles are
moving.
4. Particles are attracted to each other by electric forces, and the closer the
particles are to each other, the stronger the attractive force. This explains why
solids (...except water...) are more dense than liquids or gas.
5. Particles at higher temperatures move faster than particles at lower
temperatures. In other words, particles move faster as temperature increases.
The movement is called Heat Energy.
Matter has five phases…four are familiar
 Solids that are dense with a definite volume and shape
 Liquid has a definite volume but takes the shape of the object it occupies
 Gas has no definite volume and fills the shape of the object it occupies
 Plasma is a super-heated gas
Physical Properties
A description of a substance that does not involve forming a new substance.
Physical properties are readily observable
They are qualitative or quantitative.
Measuring these properties will not alter the basic nature of the substance.
They include colour, size, luster, texture, optical clarity, density, taste, solubility,
melting point, state and odour, ductility, viscosity and malleability.
Chemical Properties
Observable during a chemical reaction.
Chemical property is a description of what a substance does as it changes into one or
more new substances.
Examples are heat of combustion, reactivity with water, pH, light sensitivity,
flammability, oxidation (e.g., rusting) and electromotive force.
Physical Change
A change that does NOT result in the production of a new substance. If you melt a
block of ice, you still have H2O at the end of the change. If you break a bottle, you still
have glass.
Chemical Change
A change that results in the production of another substance. When you burn a log in a
fireplace, you are carrying out a chemical reaction that releases carbon. When you light
your Bunsen burner in lab, you are carrying out a chemical reaction that produces water
and carbon dioxide.
Common examples of chemical changes are digestion, respiration, photosynthesis,
burning and decomposition.
You can tell that a chemical change occurred if
•
Colour changes
•
Heat is produced or burning occurs / light is created
•
A solid forms when two liquids are mixed (called a PRECIPITATE)
•
Odour is produced
•
Gas is produced
Characteristic Property
A physical or chemical property that is unique to a substance AND that can be used to
identify the substance
Temperatures at which physical changes such as freezing, melting and boiling take place
are characteristic properties.
Density is a characteristic property. Formula is D = m/v where D is density, m is mass
and v is volume
Collision Theory
For a chemical reaction to take place, reactants must collide. The collision between the
molecules in a chemical reaction provides the kinetic energy needed to break the
necessary bonds so that new bonds can be formed. Not all collisions result in a chemical
reaction (e.g., there may not be enough energy to break bonds).
The four factors impacting the rate of a reaction -1. Concentration
2. Temperature
3. Size of the particles (i.e., surface area)
4. Catalyst being present (i.e., speed up reaction without being used up itself.
Rather, the catalyst lowers the point at which the reaction starts (called
Activation Energy)