Heat and Temperature Flashcards
What is heat?
A form of energy that flows from one point to another due to difference in temperature
What other names can heat energy be called?
a. Thermal energy
b. Radial energy
Device used to measure heat
Calorimeter/Thermometer
Give 4 effects of heat energy
a. expansion and contraction
b. the rate of evaporation
c. change of state of a body
d. change in temperature of a body
e. causes chemical changes
f. changes the electrical conductivity and resistivity of a conductor
Mention the types of heat
a. Sensible Heat
b. Latent Heat
What is Sensible Heat?
A heat energy that causes changes in the temperature without causing change in the state of the body.
What is Latent Heat?
opposite of sensible heat
A heat energy that causes changes in the state of the body without causing changes in the temperature
What are the two types of latent heat?
a. Latent Heat of Fusion
b. Latent Heat of Vaporisation
Define latent heat of fusion.
This is the energy needed to turn a solid into liquid without changing its temperature.
Define latent heat of vaporisation
This is the energy needed to turn a liquid into gas without changing the temperature..
Give 6 sources of energy.
a. Solar Energy
b. Fossil fuel
c. Wind Energy
d. Geothermal Energy
e. Chemical Energy from chemical reactions
f. Fussion and Fission from nuclear reactions
g. Electrical Energy
Define Temperature
The temperature of a substance refers to the number which expresses its degree of hotness or coldness
Measurement of temperature
A thermometer in Kelvin or degree Celsius
Formula for finding temperature in Kelvin
T/K=T/C + 273
What is Temperature Scale?
A scale of measurement, any number read from it is expressed in degree Celsius or kelvin.
What are the types of temperature scale?
a. Celsius scale
b. Kelvin scale
Define Celsius Scale
It is a temperature scale where any temperature read from it has unit of degree Celsius.
What are the two temperatures required in the Celsius scale?
0 degree Celsius and 100 degree Celsius
What is meant by lower fixed point?
The temperature which pure ice melts. 0 degree Celsius or 0 Kelvin. aka ice point
What is meant by upper fixed point?
The temperature at which pure water boils at a pressure equal to the atmospheric pressure. aka steam point. 100 degree celsius
What is the tripple point of water?
This is the temperature at which pure ice, pure water and pure water vapour co-exist in equilibrium. It has a magnitude of 273.16K
Describe the experiment to determine the lower fixed point
Apparatus: dry ice, funnel, thermometer, beaker
Method:
a. Pure dry ice that has been crushed is put in a funnel.
b. A thermometer is inserted in the funnel.
c. A beaker is put under the funnel.
d. Mercury level drops slowly.
e. At a point, ice begins to melt, and the mercury is stationary as long as it melts.
f. Level of mercury is marked as the lower fixed point.
Describe the experiment to determine the upper fixed point.
What is the Kelvin Scale?
A temperature scale where any temperature read from it has a unit of kelvin
Mention 3 other names for the Kelvin scale
a. Thermodynamic scale
b. Absolute scale
c. Ideal Gas scale
What are the two temperatures needed for the Kelvin scale?
a. Absolute zero scale(0k)
b. Tripple Point of Water (273.16K)
What is the absolute zero scale?
It is the lowest possible temperature at which atoms or molecules in a substance have the lowest possible energy
Give 3 differences between heat and temperature
a. Heat is measured in joules whereas temperature is measured in kelvin or degree celsius
b.Heat is a derived quantity whereas temperature is a basic quantity
c. Heat s measured with a calorimeter whereas temperature is measured with a thermometer.
d. Heat is a form of energy that flows from one point to another due to the difference in temperature whereas temperature is the degree of hotness or coldness of an object.
What is the formula for questions involving the distance separation between two temperatures on the thermometer
Temperature Diff
—————————– = Constant
Distance Separation
What is thermal equilibrium?
This is a state in which objects of different temperatures have the same temperature as a result of the transfer of heat from the hot one to the cold one.
Give and explain an example of thermal equilibrium.
Recording the body temperature with a thermometer.
When did thermometer is left in the armpit for some time, heat transfers from the body to the thermometer. When thermal equilibrium is reached, the body and the thermometer have the same temperature. Therefore, the temperature read from the thermometer is the same as the temperature of the body.
What is calibration?
Calibration is a means by which reading can be taken from an instrument.
Mention two ways of calibrating an instrument.
- By putting a scale on it so that reading is taken directly from it
- To derive an equation which can be used to work out the measurement.
What is meant by direct reading instruments?
This is an instrument which has a skill on it, therefore reading can be taken directly from it.
If an instrument has no skill on it, then it is not a direct reading instrument.
What is meant by standard?
refers to one which is accepted internationally and so others are compared.
for example, pure water boils at 100 degrees Celsius and this is a standard figure. So, if we compare 90 degrees Celsius to 100 degrees Celsius, we can see that the water is hot but not boiling.
What is accuracy?
The ability property of an instrument to measure the actual quantity.
What is defined as sensitivity?
This is the ability of an instrument to record and read the smallest changes in the quantity.
What are the properties of a sensitive thermometer?
- the substance put in the thermometer, called the thermometric substance must have a small heat capacity
- The walls or the frame of the thermometer must be a good conductor of heat.
What is meant by response time?
This is the time taken for an instrument to settle down before reading is taken
If an instrument takes a long time. To settle before the reading is taken, then to set to have a long response time
If the instrument takes a short time to take reading, then the instrument has a short response time.
What is stability?
This is the property of an instrument to show the same behavior after it has been used for a long period of time.
Define reproducible values.
These are standard values that are measured accurately by an instrument
An example is the temperature, 0 degrees Celsius and 100 degrees Celsius which are reproducible temperatures.
Define linear expansivity.
The linear expansivity of a substance is the fraction of its original length by which a rod of the substance expands per Kelvin rise in temperature.
What is a thermometric substance?
This is a substance in a thermometer whose physical property varies with temperature.
give examples of thermometric substances
Mercury
Alcohol
Gas
Sound
Electromagnetic radiation.
Resistance wire.
Define thermometric property.
This is a physical property of a thermometric substance which changes at temperature changes and is used to measure temperature.
Give examples of thermometric properties.
Lens
Volume of liquid
Volume of gas
Pressure of gas
Electrical resistance of a wire
Saturation vapor pressure
Electromotive force
Colour of radiation
Velocity of sound in air.
Mention 4 qualities of a good thermometer.
That’s the only time must be accurate. It must
It must be sensitive
It must have a short response time
It must have a small heat capacity
The thermometric property of the thermometer must vary linearly or proportionally with temperature.
