Download Properties of Matter

Properties of Matter
Matter is anything that occupies space and has
weight. Matter involves things we can see or feel
but we do not have to be able to see matter, for
eg., we are not able to see air but air is also matter.
Matter is classified as solid, liquid or gas.
There are three states of matter
1. Solids – definite shape and definite volume
- do not flow
- tightly packed particles
- motion of particles is highly restricted
so that solids are generally
incompressible
- most solids expand slightly when heated
- can have high or low density, for eg.,
gold vs cork
2. Liquids – no definite shape, but they do have a
definite volume
- flow
- particles are relatively close to one
another and are moderately ordered
with some interaction between them
- incompressible
- expand slightly when heated
- can have high or low density, eg., petrol
0.68g/ml and mercury 13.6g/ml
3. Gases – no definite shape or volume
- flow
- particles motion is unrestricted so that
they are independent and relatively far
apart
- high compressible
- expand greatly when heated
- low density
Changes of State of Substances
When a substance MELTS, it changes from a SOLID
state to a LIQUID state
When a substance BOILS, it changes from a
LIQUID state to a GASEOUS state
Energy
Definition : Energy is the ability to do work, for
eg., muscles in the body get their energy from
chemical reactions in the muscle cells.
Two types :
Kinetic energy – energy of motion, ie., energy that is
doing something
Potential energy – stored energy, ie., energy not
associated with motion, eg., food,
water at the top of a waterfall or
chemical energy
Most chemical reactions involve heat energy
If heat is given off the reaction is EXOTHERMIC
If heat is absorbed, then the reaction is
ENDOTHERMIC
Energy can be transformed from one form to
another, for eg., burning a piece of coal turns its
potential energy into heat which is kinetic energy.
Law of conservation of energy : energy is neither
created nor destroyed in a chemical reaction, it
can be changed from one form to another but the
total amount remains the same.
Law of conservation of matter : matter is neither
created nor destroyed during a chemical reaction,
ie., the total weight of substances before they
react is the same as after they react.
Measurement of Energy
Heat is the most common form of energy. All
other forms can be converted into heat energy.
Units for measuring energy are the Calorie (cal)
and Joule (J) but Joule is the SI unit (1 cal =
4.18J)
The calorie is defined as the amount of heat
required to increase the temperature of 1g of
water by 10C.
Three basic kinds of food produce energy in the
body
- carbohydrates : oxidation of 1g provides 4k cal
of energy
-fats : oxidation of 1g provides 9k cal of energy
- proteins : oxidation of 1g provides 4k cal of
energy
The number of calories produced in a chemical
reaction can be calculated in terms of water that
can be heated from one temperature to another.
Energy (cal) = mass of water (g) X ∆ T (0C) X
specific heat of water
Specific heat of water = 1 cal/g 0C
Example
1. How many calories are required to raise the
temperature of 100g of water from 220C to 350C?
How many grams of fat must be oxidised to
produce this energy? (1.3 kcal; 0.144g)
Composition of Matter
There are three classes :
Elements – are building blocks of matter which
cannot be broken down into any simpler
substance by ordinary chemical means.
Elements can be classified as metals or nonmetals.
Compounds – are substances that can be broken
down into simpler substances by chemical
means. They are homogenous in composition.
Mixtures – are made up of two or more
compounds or elements. They have no definite
proportion or composition. They can be
homogenous (sugar/water) or heterogeneous
(sugar/sand)