Students can go through AP Board 7th Class Science Notes 9th Lesson Heat, Temperature and Climate to understand and remember the concept easily.
AP Board 7th Class Science Notes 9th Lesson Heat, Temperature and Climate
→ Heat is a form of energy that flows from a hotter body to a cooler body.
→ Heat flows from a body of high temperature to a body of low temperature.
→ Heat is measured in Joules.
→ The degree of hotness or coldness is called temperature.
→ The variations of hotness, coldness can be termed as degree of hotness and coldness.
→ Temperature is measured in degrees of Celsius, degrees of Fahrenheit or Kelvin using a thermometer.
→ The SI unit of temperature is Kelvin (K).
→ Degree Celsius : Celsius is written as °C and read as degree Celsius. Celsius is also called Centigrade.
→ Degree Fahrenheit : Fahrenheit i$ written as °F and read as degree Fahrenheit.
→ Kelvin : Kelvin is written as K and read as Kelvin.
→ The ability of a material to conduct heat is called thermal conductivity.
→ Depending on thermal conductivity materials are of two types : They are
- Good conductors
- Poor conductors (insulators}.
→ The materials which allow heat to pass through them are called conductors of heat.
Ex : Aluminum, iron and copper etc.
→ The materials which do not allow heat to pass through them easily are poor conductors of heat. Ex: Water, air, clothes, glass, cork, plastic, wood etc. They are also known as insulators.
→ Transfer of heat is different in different types of materials. Heat gets transferred in three different modes. They are
- Conduction of heat
- Convection of heat
- Radiation of heat.
→ The process of transfer of heat from hotter to colder end through the conductor is called conduction. This mode uansfer of heat happens more in solid conductors.
→ The contact which transfers heat by any mode is called Thermal contact.
→ Coriduction doesn’t take place without thermal contact.
→ This process of transfer of heat from source of heat to surface by the motion of par¬ticles is called “convection of heat”. In liquids and gases heat is transmitted by mode of convection of heat.
→ Such types of materials which help in transfer of heat from one place to another are called “medium”. Solid, liquid and gaseous substances act as medium for transfer of heat.
→ The process of transfer of heat in the form of waves is called radiation. Radiation does not need any material medium. Sun’s heat transfers to earth in the form of radiation.
→ Thermos flask was invented by Sir James Dewar.
→ Particles of substances occupy more space when they get heated.
→ Solid expands on heating and contracts on cooling.
→ Gases expands on heating and occupies more space. They contracts on cooling and occupy less space.
→ Thermometers are used to measure temperature, this works on the expansion of liquids (mercury or alcohol).
→ Clinical thermometer is used in hospitals to measure the temperature of the human body.
→ Laboratory thermometer is used in school labs, industries etc. to measure temperature.
→ Six’s maximum minimum thermometer is one of the Meteorological Instruments used to measure maximum (highest) and minimum (lowest) temperatures of a place in a day. James Six invented this thermometer.
→ The normal temperature of the human body is 37°C or 98.4°P.
→ Smoke and hot air moves up because it expands and becomes lighter.
→ The force applied by air on any surface in contact is called “air pressure”.
→ The air pressure becomes more when it is compressed.
→ Air pressure is measured in height of mercury level in centimeters.
→ Mercury Barometer and aneroid barometers are used to measure air pressure.
→ Rainfall is measured in millimeters by using a rain gauge.
→ The water vapour present in the air is called humidity. Hygrometer is used to measure humidity in air.
→ High temperatures, along with humidity sometimes may cause heat stroke or sunstroke.
→ Maximum and minimum temperature of a day, air pressure, rainfall, wind speed and humidity are called measuring components of weather.
→ The day-to-day variations in the components like temperature, humidity, rainfall, wind speed are called weather. •
→ The average weather pattern taken over a long period is called the climate of the place.
→ The abnormal variation in the components of climate is called climate change.
→ Heat : Heat is a form of energy that flows from a hotter body to a cooler body.
→ Temperature : The degree of hotness or coldness is called temperature.
→ Degree Celsius : Temperature is measured in Degree Celsius (°C).
→ Fahrenheit : Temperature is measured in Fahrenheit (°F).
→ Kelvin : The SI unit of temperature is Kelvin (K).
→ Good conductors : The materials which allow heat to pass through them are called good conductors of heat.
Ex : Aluminum, iron and copper etc.
→ Poor conductors : The materials which do not allow heat to pass through them easily are poor conductors of heat.
Ex : Water, air, clothes, glass, cork, plastic, wood etc. They are also known as insulators.
→ Conduction : The process of transfer of heat from hotter to colder end through the conductor is called conduction. This mode of transfer of heat happens more in solid conductors.
→ Convection : This process of transfer of heat from source of heat to surface by the motion of particles is called “convection of heat”.
→ Radiation : The process of transfer of heat in the form of waves is called radiation.
→ Expansion : Particles of substances occupies more space when they get heated is called expansion.
→ Contraction : Particles of substances occupies less space when they get cooled is called Contraction.
→ Thermometer : Thermometers are used to measure temperature.
→ Air pressure : The force applied by air on any surface in contact is called “air pressure”.
→ Components of weather : Maximum and minimum temperature of a day, air pressure, rainfall, wind speed and humidity are called measuring components of weather.
→ Climate : The average weather pattern taken over a long period is called the climate of the place.
→ Humidity : The water vapour present in the air is called humidity.
