The matter is made up of particles.
There must be millions of tiny particles in just one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles. Continue Learning
Mixtures are constituted by more than one kind of pure form of matter.
For a scientist all these things are actually mixtures of different substances and hence not pure. For example, milk is actually a mixture of water, fat, proteins etc. When a scientist says that something is pure, it means that all the constituent particles of that substance are the same in their chemical nature. A pure substance consists of a single type of particles. Continue Learning
There are two laws of chemical combination were established after much experimentations by Lavoisier and Joseph L. Proust.
Law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. Continue Learning
An electron is represented as ‘e—’ and a proton as ‘p+’. The mass of a proton is taken as one unit and its charge as plus one. The mass of an electron is considered to be negligible and its charge is minus one.
An atom was composed of protons and electrons, mutually balancing their charges. It also appeared that the protons were in the interior of the atom, for whereas electrons could easily be removed off but not protons. Continue Learning
All organisms that we observe around are made up of cells. However, there are also single cells that live on their own.
Cells divide to produce cells of their own kind. All cells thus come from pre-existing cells. Some organisms can also have cells of different kinds. Look at the following picture. It depicts some cells from the human body. Continue Learning
Plants are stationary or fixed — they don’t move. Since they have to be upright, they have a large quantity of supportive tissue. The supportive tissue generally has dead cells.
Animals on the other hand move around in search of food, mates and shelter. They consume more energy as compared to plants. Most of the tissues they contain are living. Continue Learning
Classifying living things into groups have been made since time immemorial. Greek thinker Aristotle classified animals according to whether they lived on land, in water or in the air.
The process of classification within each group can then continue using new characteristics each time. Continue Learning
Describe the position of an object we need to specify a reference point called the origin.
An object may appear to be moving for one person and stationary for some other. For the passengers in a moving bus, the roadside trees appear to be moving backwards. Most motions are complex. Continue Learning
When the block is pulled from both the sides with equal forces, the block will not move. Such forces are called balanced forces and do not change the state of rest or of motion of an object.
When two opposite forces of different magnitudes pull the block. In this case, the block would begin to move in the direction of the greater force. Continue Learning
When the stone moves in a circular path with a certain speed and changes direction at every point. The change in direction involves change in velocity or acceleration. The force that causes this acceleration and keeps the body moving along the circular path is acting towards the centre. This force is called the centripetal (meaning ‘centre-seeking’) force. Continue Learning
When a force acts upon an object while it is moving, work is said to have been done upon the object by that force.
The way we understand the term ‘work’ in science, work is not done. In day-to-day life, we consider any useful physical or mental labour as work. Activities like playing in a field, talking with friends, humming a tune, watching a movie, attending a function are sometimes not considered to be work. Continue Learning
The objects vibrating and produce sound. Vibration means a kind of rapid to and fro motion of an object. The sound of the human voice is produced due to vibrations in the vocal cords.
Sound is a form of energy which produces a sensation of hearing in our ears. There are also other forms of energy like mechanical energy, light energy, etc. Continue Learning
‘Health’ is therefore a state of being well enough to function well physically, mentally and socially.
While being interested in following the teaching in the classroom so that we can understand the world is called a ‘healthy attitude’; while not being interested is called the opposite. Continue Learning
The consumption of oxygen and the concomitant production of carbon dioxide is combustion. This includes not just human activities, which burn fuels to get energy, but also forest fires. So, the air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour and so on and each one has the important role. Continue Learning
Different crops require different climatic conditions, temperature and photoperiods for their growth and completion of their life cycle. Photoperiods are related to the duration of sunlight. Growth of plants and flowering are dependent on sunlight.
There are some crops, which are grown in rainy season, called the kharif season from the month of June to October, and some of the crops are grown in the winter season, called the rabi season from November to April. Continue Learning