science wa2

• friction and elastic force is a contact force
• gravitational force and magnetic force is a form of non contact force
• a force is a push or pull
• a force can stop moving object, change the direction of a moving object
• a force can change the shape or size of an object
• pressure is an effect of force acting on a object
• the amount the pressure depends on the area of contact
• the smaller the are of contact, the higher the amount of pressure exerted
• pressure is force/area
• energy is the capacity to do work
• work is the measure of energy transfer that occurs when an object is moved over a distance by force
• energy cannot be destroyed or created
• energy can be transferred, change the state of matter and converted
• the total energy of an object will always be the same as the energy is conserved
• a physical change is when no new substances are formed and the changes can be reversed using separation techniques
• a chemical change is when one or more new substances are formed
• combustion is when substances are heated in the presence of oxygen to form one or more new substances
• thermal decomposition is when a substance break down into two or more simpler substances upon heating
• oxidation is when substances gains oxygen
• neutralisation is when acids are mixed with alkalis to form a neutral reaction of salt and water
• acids turn blue litmus paper red
• acids reacts with metals, alkalis and carbonate
• alkali turns red litmus paper blue
• alkali reacts acids
• acids+ alkali=salt+ water
• acids+ metals= salt+ hydrogen
• acids+ carbonate= salt + carbon dioxide+ water
• to test for hydrogen, place a lighted splint at the mouth of a test tube, it would extinguish a pop sound
• to test for carbon dioxide, use aqueous calcium, it would produce a white percipitate when carbon dioxide is bubbled through it
• temperature is the measure of hw hot an object is
• in hot weather, a metal track gains heat and expands. This can cause the track to buckle and derail. Hence, train tracks have expansion gaps between them to provide space for expansion
• Bimetallic strips are used in irons and thermometers. They are made up of two metals that expands at different rates upon the same change in temperature
• conduction is the transfer of heat energy without the physical movement of a medium
• convection is the transfer of heat energy from one place to another by physical movement of a medium