PHYSICS AND CHEMISTRY
ONLINE ASSESSMENT 1REVISION:29-07-20
7.1 LIGHT RAYS
Properties of Light
Investigating shadow
 The height of the shadow increases as
the distance of the object from its
shadow increases.
7.2 REFLECTION
Reflection
Images formed in plane mirror
mirror
The nature of image formed by a
plane mirror is:
 Virtual and erect (upright)
 Size of image formed is equal to the size of
object.
 Image is formed behind the mirror.
 Image is at same distance behind the mirror
as the object is in front of the mirror.
 Image formed in plane mirror is laterally
inverted.
Periscope
7.3 REFRACTION
Refraction
1. Rarer to denser medium
∠ i > ∠r
Refraction
2. Denser to Rarer(less dense) medium
∠ i < ∠r
Refraction
3. Along the normal
Refraction through glass slab
Examples of Refraction
CHEMISTRY
4.ELEMENTS, COMPOUNDS AND
MIXTURES
4.1 MORE ON CHANGES
OF STATE.
Particle arrangement
Changing state
4.2 GAS PRESSURE AND
DIFFUSION
Gas pressure
 The effect of the forces caused by collisions
from gas particles on the walls of a container.
 The basic unit of pressure is the newton per
square meter (N/m2).
Factors affecting the gas
pressure
 1) Number of particles:
 Increasing the number of particles in the
same space increases gas pressure.
2)Temperature
Increasing the temperature also increases
gas pressure.
 3)Volume
Decreasing the volume also increases
gas pressure.
DIFFUSION
 “Diffusion is the movement of particles from
the area of higher concentration to lower
concentration area, continuing until equilibrium
is reached”.
Factors affecting rate of
diffusion
 TEMPERATURE
 MASS OF PARTICLES
Examples of Diffusion
 Perfume is sprayed in one part of a room, yet
soon it diffuses so that you can smell it
everywhere.
 A drop of food coloring diffuses throughout the
water in a glass so that, eventually, the entire
glass will be colored.
 When steeping a cup of tea, molecules from the
tea cross from the tea bag and diffuse
throughout the cup of water.
 When shaking salt into water, the salt dissolves
and the ions move until they are evenly
distributed.
 After placing a drop of food coloring onto a
square of gelatin, the color will spread to a
lighter color throughout the block.
 Carbon dioxide bubbles diffuse from an open
soda, leaving it flat.
 A helium balloon deflates a little bit every day
as helium diffuses through the balloon into
the air.
 If you place a sugar cube in water, the sugar
will dissolve and evenly sweeten the water
without having to stir it.
4.3 ATOMS, ELEMENTS AND THE
PERIODIC TABLE
 atom – The smallest particle that can exist on its own.
 compound – Substance made up of two or more
different elements that are chemically joined together.
 element – Substance made up of only one type of
atom.
formula – The symbols and numbers that represent
the atoms in a substance.
 molecule – Two or more atoms that are chemically
joined together.
 periodic table – Table in which all known elements are
arranged based on their properties.
 symbol – One or two letters that represent an element.
Trick to remember 20
elements.
 Happy Henry Lives Beside Boron Cottage,
Near Our Friend Nelly Nancy MgAllen. Silly
Patrick Stays Close. ...
 Here He Lies Beneath Bed Clothes, Nothing
On, Feeling Nervous, Naughty Margret
Always Sighs, ” Please Stop Clowning Around
” (18 elements)
THANK YOU