P1-MATTER

Question 1

John Dalton in the 1870s

Answer 1

-his model was a solid sphere

said that:
-all atoms in an element are the same
-the atoms in one element are different from the atoms in all other elements

Question 1

J.J Thompson in 1897

Answer 1

-was investigating rays given out by hot metals,called cathode rays
-Thompson discovered that cathode rays are made of particles that have 1/1000 of the mass of a hydrogen atom.
-He had found a particle which he called an electron that must have come from inside an atom.He also worked out that the charge on an electron is negative.

he thought:
-an atom contains negative electron
-overall,atoms have no electrical charge and are neutral

1904-plum pudding model.Sphere of positive mass,with negative electrons embedded in it

Question 2

Rutherford in 1899

Answer 2

-fired alpha particles at a thin piece of gold foil and some bounced back,indicating some sort of positive force repelling the particles back

-he said:
-the atom is made of a tiny,positively charged nuclues with electrons around the outside

Question 2

what is temperature

Answer 2

-tells you how hot or cold something is.Measured with a thermometer or a temperature sensor
-has units of temperature Celsius (‘C) and Kelvin(K)

-273 c=0K
0C=273K

Question 3

Bohr in 1913

Answer 3

-the problem with rutherfords model was that you would expect the electrons to spiral in until they hit the nucleus.
-Bohr suggested:
-electrons can only move in fixed orbits,called electron shells,around the nucleus.

Question 4

diameter of an tom

Answer 4

10^-10 m

Question 5

What is density

Answer 5

density is the amount of mass in a certain volume

density is a property of a material,not of an object,so the mass of each object depends on its volume

Question 6

density formula

Answer 6

Density(kg/m3)=mass(KG)/Volume(m3)

Question 6

why is a substance denser as a solid than as a liquid or gas

Answer 6

as in 1cm3 of solid,there are more particles,meaning more mass,therefore denser

-density depends on:
particle arrangement
mass of particles

Question 7

what is the conservation of mass when substances change state by melting,freezing,evaportaing,condensing or sublimating

Answer 7

You have to add or remove material for the mass of a system to change.The particles do not appear nor disappear.

For example,if you melt 1g of ice,you will get 1g of water-water molecules do not disappear