Chemistry

Question 1

what are Atoms?

Answer 1

‘Matter’ is the general scientific word that describes the ‘stuff’ that
makes everything around us.
Matter is made up of tiny particles called atoms.

Question 2

how big is an Atoms?

Answer 2

If an atom was the size of a pea…
…a water molecule would be the size of a small grape…
…a sugar molecule would be the size of a credit card…

Question 3

what is the periodic table?

Answer 3

The Periodic Table shows the names of all of the different types of atom that exist, and their symbols (there are over a hundred).

Question 4

What are atoms and molecules?

Answer 4

Some common chemicals (such as water and carbon dioxide) are not in the Periodic Table, as they are combinations of atoms called
molecules…

Question 5

what are the atoms structure

Answer 5

Atoms are made up of even smaller particles. Protons and neutrons form a cluster at the centre of the atom, known as the nucleus. Electrons, which are much smaller
than protons and neutrons, orbit the nucleus

Question 6

atomic number and atomic mass

Answer 6

The larger number is the atomic mass – this tells us how many protons and neutrons are in
the nucleus. The smaller number is the atomic number – this
tells us how many protons are in the nucleus (and how many electrons are orbiting).

Question 7

solid

Answer 7

Closely packed
Arranged neatly
At the bottom of box
Little movement
Incompressible
Cannot be mixed

Question 8

liquid

Answer 8

Some contact
Random
At the bottom of box
Some freedom
Incompressible
Can mix

Question 9

gas

Answer 9

No contact
Random
Fill the space
Free to move
Compressible
Can mix

Question 10

what is changing state

Answer 10

If we raise the temperature of a solid (by adding energy), a liquid forms; this will then turn into a gas when the temperature is raised further. Lowering the temperature of a gas (removing energy) will form a liquid, then a solid.

Question 11

melting

Answer 11

solid into liquid

Question 12

freezing

Answer 12

liquid into solid

Question 13

boiling

Answer 13

liquid into gas

Question 14

condensing

Answer 14

gas into liquid

Question 15

deposition

Answer 15

gas into solid

Question 16

kinetic theory - heating

Answer 16

All particles have kinetic energy – they are all vibrating. We can supply extra energy to the particles to raise their temperature, by heating them up. The higher the temperature, the more the
particles will vibrate. When the melting point is reached, the
energy is used to break the forces that hold the particles close together, giving them more freedom to move.

Question 17

kinetic theory- cooling

Answer 17

When the substance is cooled, energy is removed from the particles, causing them to vibrate less. When the temperature of a gas is reduced to the boiling point, the particles start to ‘cuddle’ together again, but still have
some freedom to move (as a liquid). When cooled below the melting point, the
particles cluster close together to form a solid.

Question 18

evaporation

Answer 18

Evaporation is another word that describes a liquid turning to a gas, but be careful they are not the same thing!
When a substance evaporates, only the particles at the surface turn to vapour. This can be achieved at any temperature if another form of energy is present.

Question 19

diffusion

Answer 19

Diffusion is the movement of a fluid from a place where it is highly
concentrated, to a place where it is less concentrated.

Question 20

brownian motion

Answer 20

Brownian motion describes the
random motion of the particles
in a fluid, as they bump into
each other.

Question 21

examples of diffusion

Answer 21

Spraying perfume, air freshener (or passing wind!) –
at first the smell was the strongest nearest the source,
but soon spreads for everyone to smell it.

Question 22

thermal expansion

Answer 22

When we heat a substance, we give the particles more energy. This causes the particles to vibrate more; as they do so, they spread apart, causing the substance to
expand.

NOTE: THE PARTICLES DON’T EXPAND!

Question 23

expanding metals - the bar and gauge

Answer 23

THE BAR AND GAUGE
When the bar is heated, the metal expands and
the particles spread slightly. As a result, the bar no longer fits into the gauge.When the bar cools, it will fit again.

Question 24

expanding metal - the ball and ring

Answer 24

THE BALL AND RING
When cold, the ball just fits through the ring. When the ring is heated, it expands to allow the
ball to pass through easily.When the ball is heated, it expands and will no longer fit through the ring.

Question 25

can liquid and gases expand

Answer 25

We know that a liquid-in-glass thermometer works by the column of liquid rising through
the tube as temperature increases – this is because the liquid expands.

Question 26

air pressure

Answer 26

When particles hit against a surface, they push on it with a small amount of force – this is known as pressure. We know that air exerts a pressure; when the particles are closer together, the pressure is higher – this is why a balloon stays inflated

Question 27

density

Answer 27

The density of a substance may be described as ‘how heavy it is for its size’.

Question 28

what equation do we use for density

Answer 28

density(g/cm³) = mass(g) / volume(cm³)

Question 29

measuring density

Answer 29

REGULAR SHAPES
-Select your block of material.
-Measure and record its length, width and height in cm.
-Multiply these measurements to find the volume in cm³.
-Find the mass of the block in grams by placing it on the balance.
-Divide the mass by the volume to find the density.