7th Class

Acids, Bases and Salts   Acids Acids are found in small amounts in nature. For example, acids are present in things that we eat such as lemon and orange contains citric acid, tomato contains oxalic acid, vinegar contains acetic acid, yoghurt contains lactic acid and frizzy drinks contain carbonic acid. Acids found in foods are mild. Acids such as hydrochloric acid \[(HCL),\] sulphuric acid\[({{H}_{2}}S{{O}_{4}})\] and nitric acid \[(HN{{O}_{3}})\] are called mineral acids. They are strong acids. Touching strong acids can cause acid burns. Acids are formed by dissolving oxides of non-metals such as carbon, sulphur and nitrogen in water. The oxides of non-metals are acidic because when dissolved in water they form acids For example: \[C{{O}_{2}}+{{H}_{2}}O\to {{H}_{2}}C{{O}_{3}}\] \[S{{O}_{3}}+{{H}_{2}}O\to {{H}_{2}}S{{O}_{4}}\] \[3N{{O}_{2}}+{{H}_{2}}O\to NO+2HN{{O}_{3}}\]   Behaviour of Acidic Substances The acidic substances show the following behaviour:  

• Taste sour.
• Turn blue litmus paper into more...

Weather, Climate and Adaptations of Animals to Climate   Weather Weather indicates the day to day atmospheric conditions. Atmospheric conditions include temperature, rainfall and the speed of the wind. In addition to this, weather report for a place indicates humidity levels, time of sun rise and sun set.   Temperature The maximum and minimum atmospheric temperature can be measured with the help of thermometer.   Humidity Humidity is the amount of water vapour present in the air. The capacity of the air to hold water vapour increases with temperature. The amount of water vapour present in the air expressed as a percentage of the amount of water needed for saturation at the same temperature is called relative humidity. The relative humidity is measured with an instrument called hygrometer.   Rainfall, Snow and Fog The humidity in air determines the chances of rainfall. Air when more...

Winds, Storms and Cyclones   Wind Moving air is called wind. Wind occurs due to the heating caused by the sun. The unequal heating of different parts of the earth causes the wind to blow. When the wind blows with slow speed it is called breeze. When the wind blows with high speed it is called storm.   Air Pressure Air exerts pressure. Like temperature and humidity, air pressure also determines the weather of a place on a particular day. Air pressure can be measured with an instrument called barometer.   Wind is Produced Due to Uneven Heating on the Earth by the Sun Uneven heating on the earth can take place by two situations:  

Uneven heating between the equator and the poles of the earth

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Life Processes   Respiration Food provides energy to all living organisms. Food is first broken down into simple and soluble molecules. The simple molecules are then carried to all the cells. In cells, these molecules combine with oxygen to produce energy. This process of combination of simple food molecules with oxygen to produce energy is called respiration.   Types of Respiration There are two types of respirations: aerobic respiration and anaerobic respiration.   more...

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Aerobic respiration	Anaerobic respiration