NCERT Solutions Class 9 Science PDF is available to download. NCERT exemplar problems is also important books issued by CBSE. In the same section assignments, Previous years questions with solutions are also given. Important questions according to the latest NCERT Syllabus from popular books Lakhmir Singh and Manjit Kaur, S Chand, Pradeep’ fundamental book, Together with Science, U – Like and other important books will be included in the assignments. Extra questions of OTBA material for 2017 will be uploaded frequently. If you need answers of questions related to OTBA class 9 for 2017, please upload through FORUM, we will provide solutions with in 48 hours.
Main point to be remembered
- Matter is made up of particles
- The particles of matter are very small-they are small beyond our imagination
- Particles of matter have space between them
- Particles of matter move continuously in liquids and gases.
- Matter exists in three states i.e., solid, liquid and gas
- The force of attraction between the particles are maximum in solids, intermediate in liquids and minimum in gases.
- The particles are arranged orderly in the case of solids while particles move randomly in gasses.
- Diffusion is possible only when particles of matter move continously.
- Rate of diffusion of gases is higher than that of liquids (or) solids.
- The states of matter are not permanent. The state of matter can be changed by changing temperature or pressure.
- Evoparation is a surface phenomenon because particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state.
- Boiling is a bulk phenomenon because particles of the entire liquid change into vapour state.
- Changes in temperature, surface area and wind speed effect rates of evaporation.
- Humidity is the amount of water vapour present in air.