James Watson is credited with the discovery is the stricture of DNA.
he gibe the 3D structure of DNA in 1962 ,
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1- Combustion reactions are exothermic reactions since these reactions result in the emission of heat (heat is a product and not a reactant)
2- A substance with higher specific heat that water would be liquid ammonia. This means that, for the same amount of energy given to both water and liquid ammonia, water will heat faster and gain more thermal energy (in degree celcius) that liquid ammonia.
3- Conduction : occurs when heat is directly transmitted from a material to another due to the difference in temperature between both. Examples are:
a- when using an iron the heat is transferred from the iron to the piece of clothe being ironed
b- if you hold a hot cup heat will transfer to your hand
c- when you hold chocolate with your bare hand it will melt due to the transfer of heat from your hand to the chocolate
d- when you heat food on the stove the heat will transfer from the flame to the pan
e- when you hold ice it melts due to the transfer of heat from your hand to the ice piece
f- when you place hot liquid in a cup the heat will transfer from the liquid to the cup and the cup will become hot
g- if you place a spoon in a plate containing hot food the heat will be transferred from the food to the spoon making it hot
h- when you walk on the sand beach during summer the heat will be transferred from the sand to your feet and your feet will be hot
i- if you hold someone's hand when he/sh is cold the heat will be transferred from your hand to his/hers
j- Light bulbs emit heat, if you touch them this heat will be transferred to your body
4- Convection : is the transfer of heat through liquids or gases. Examples:
a- when water at the bottom of a pot is heated, it transfers this heat to the water above by convection
b- the process of ice melting when left in the air where heat is transferred from the air to the ice
c- the same goes for chocolate melting
d- cooling a frozen substance using running water where heat is transferred from the water to the frozen substance
e- when you stream a hot cup of tea/coffee, you transfer heat from the tea/coffee to the air
f- when a radiator moves the hot air upwards and the cold air downwards
g- when a balloon rises up wen being filled with hot air
h- when the ocean circulates and heat is transferred from warm water to cool water
i- when heat is transferred from a bulb to the surrounding air
j- when you cool the radiator of your car using water where water is transferred from the radiator to the water.
5- Radiation: the emission of energy in the form of waves. Examples:
a- the sunlight (ultraviolet radiations of sunlight)
b- x-rays
c- the flame/light of a candle
d- the gamma radiations from the explosion of a star
e- microwaves of a microwave oven
f- the radiations of the mobile phone which are electromagnetic radiations
g- the beam of a laser
h- placing your hand over warm fire
i- emission of alpha particles from decaying uranium
j- the radio waves
