density and kinetic theory

Question 1

forces can: name 5

Answer 1

1 change the size or shape of a body
2 change the speed of a body
3 stop or start a body
4 change the direction of movement of a body 
5 cause something to turn or rotate

Question 2

define the term force

Answer 2

a force is that which changes or tends to change the shape or state of rest or motion of a body

Question 3

what are the 2 types of forces

Answer 3

contact forces eg friction, push, pull
forces acting at a distance-
- gravitational exists between all masses
-magnetic-exists between magnetic poles
-electrostatic exists between electric charges

Question 4

what are the definitions of mass and weight

Answer 4

mass- this is a measure of the quantity of matter in a body and it is constant
- mass of an object on earth = mass of an object on the moon

weight - this is a measure of the force exerted by the gravity on a body
- a 1 kg mass is pulled towards earth by a force of 10N

Question 5

definition of balanced and unbalanced forces

Answer 5

balanced - no change

unbalanced- change in movement

Question 6

what is the definition of the centre of gravity

Answer 6

the centre of gravity of an object is point where all the weight appears to act

Question 7

when will a body topple and how can stability be increased

Answer 7

when the vertical line through the centre of gravity falls outside of its base

stability can be increased by
> increasing the base area
>lowering the position of the centre of gravity

Question 8

what is the definition of the turning effect

what is the equation for calculating the moment

Answer 8

the turning effect or the moment of a force is equal to the force multiplied by the perpendicular distance from the force to the pivot

moment = force x perpendicular distance

Question 9

when does the turning effect increase in our hands

Answer 9

the weight is moved away from our hand

the weight is increased

Question 10

definition of volume

Answer 10

the volume of an object is the amount of space the object occupies

Question 11

what is the method for calculating the volume of irregular objects that sink

Answer 11

1 partly fill a measuring cylinder with water and note the volume
2 lower the object into the water and note the volume
3 take away the first volume ( just the water ) from the second volume ( the water with the object in the water )

Question 12

what is the definition of density and the equation to calculate it

Answer 12

a mass of unit volume
density = mass
———
volume

Question 13

what does kinetic theory state

Answer 13

> all the matter is made up of tiny, invisible moving particles these particles can be atoms, ions or molecules
the particles are continually moving if the temperature is raised the particles gain energy and move more quickly.
at a given temperature lighter particles move more quickly that heavier particles

Question 14

illustrate was a solid is

Answer 14

> the particles are in a fixed position
the only motion allowed to them is vibration
the particles are held in the solid by strong forces and this explains why they have a fixed shape and volume

Question 15

describe a liquid

Answer 15

> the particles are mainly touching, but some gaps appear in the structure
these gaps allow the particles to move and although there are forces between them, the particles have enough energy to prevent the forces holding them in a fixed arrangement
this behaviour of particles explains why liquid have a fixed volume but take the shape of the container

Question 16

what is a gas

Answer 16

> the particles have larger gaps between them and are entirely free to move
the forces between the particles are weak, and this explains why gases completely fill their container

Question 17

what are the changes of state that happen when heating

Answer 17

solid-

• vibrate faster
• the separation of the particles increases, increasing the volume.
• reduction in density
• when sufficient energy is gained bonds break between them
• a liquid is less dense that a solid

Iiquid-

• move around faster
• particles are able to escape and form a gas, is evaporation. on further heating all particles gain sufficient energy to overcome all of the attractive forces between particles and the liquid boils .
• the distance increases and the densisty decreases
• a gas is less dense than a liquid.

particles gain kinetic energy> vibrate faster> bonds break> move further apart> density decreases

Question 18

what happens when you cool a gas and a liquid

Answer 18

gas - particles lose kinetic energy and move closer and closer together. attractive forces between the particles cause bonds to form and condensation takes place the gas turns to liquid. the density of a gas is than the density of a solid

liquid- particles lose kinetic theory, vibrate less and move closer together density of a liquid is less than the density of a solid

particles lose kinetic energy> vibrate slower> bonds form> move closer together > density increases

Question 19

why is ice the exception

Answer 19

particles lose kinetic energy and vibrate less forming more bonds. these bonds increase the distance between the particles and so decrease the density

when ice melts the particles gain kinetic energy, vibrate faster, break bonds and the density increases

density of of ice is less than that of water

Question 20

Example

If the density of the object is 2 kg and the volume is 150m wat is the mass

Answer 20

300

Question 21

Example

The density of an object is 0.5g/cm3 and the mass is 50g state what the volume is

Answer 21

100cm3

Question 22

How do you find density on a graph

Answer 22

The gradient of the graph