19.1

Question 1

Energy transfer between 2 objects takes place if

Answer 1

One object exerts a force on the other object and makes it move (one object does work on the other object)

One object is hotter than the other object so energy transfer by heating takes place by conduction convection or radiation (basically when energy is transferred by heating because of a temp difference between 2 objects)

Question 2

Internal energy of an object is the energy of its molecules due to their

Answer 2

Individual movements and positions

Question 3

The internal energy of and object due to its temp is sometimes called

However some of the internal energy of an object might be due to other causes eg
An iron bar that is magnetised has more …than if it is.. ,because of the magnetic interaction between the irons bars …

Answer 3

Thermal energy

Internal energy

Unmagnetised

Atoms

Question 4

Internal energy of an object is increased because of

Answer 4

Energy transfer by heating the object
Or
Work done on the object
Eg work done by electricity

Question 5

If the internal energy is an object stays constant then either

Answer 5

There’s so energy transfer by heating and no work is done

Or
Energy transfer by heating and work done balance each other out

Question 6

Example of internal energy of object staying constant due to energy transfer by heating and work done balancing each other out:

Internal energy of a lamp filament increases when lamp is switched on because …
Because of this the filament becomes ..
When it reaches its operating temp,energy is …

Work done by electricity supply pushing electrons through filament is …by the energy transfer and light radiated from the …

Answer 6

Work is done by electricity supply pushing electrons through the filament

Hot

Transferred to the surroundings by heating and the filament radiates light

Balanced

Filament

Question 7

First law of thermodynamics

Answer 7

( In general when work is done on it by an object and /or energy is transferred by heating)
, The change of internal energy of the object = the total energy transfer due to work done and heating

Question 8

When the fort las of thermodynamics is applied to an object , the directions of the energy transfers (I.e to or from the object) are very important and determine whether

Answer 8

the overall internal energy of the object increases or decreases

Question 9

Molecule is

Answer 9

The smallest particle of a pure substance that is characteristic of the substance

Question 10

An atom is

Answer 10

The smallest particle of an element that is characteristic of the element

Question 11

In a solid the atoms and molecules are held to each other by

Answer 11

Forces due to the electrical charges of the protons and electrons in the atoms

Question 12

Higher temperature of solid means

Answer 12

More molecules vibrate

Question 13

Molecules in a solid vibrate ..

Answer 13

Randomly about fixed positions

Question 14

Energy supplied to raise temperature of solid increases the

Answer 14

Kinetic energy of the molecules

Question 15

If temperature Of solid is raised high enough

This happens because

The energy supplied to melt a solid raises the

Answer 15

The solid melts

It’s molecules vibrate so much that they break free from each other and the substance loses its shape

Potential energy of the molecules because they break free from each other