Physical and Chemical Change Flashcards
Chemical Bond
An attractive force that holds two atoms together
Chemical bonds are broken or formed during chemical changes but not physical changes.
Chemical Change
A change in matter that forms one or more new substances
New substances form when atoms are re-arranged. This type of change is often hard to reverse.
Combustion
A chemical change where a substance burns
The substance that burns is called a fuel. It combines with oxygen to produce new substances.
Condensation
A physical change from a gas to a liquid
Droplets form on the outside of a cold drink bottle because of water vapour condensing.
Deposition
A physical change from a gas to a solid
In sub-zero weather, water vapour in the air can turn directly into ice on car windows.
Digestion
The breakdown of food by physical and chemical changes
Chewing breaks down food by physical change. Stomach acid breaks down food by chemical change.
Dissolving
A physical change where a solid spreads through a liquid
When sugar is stirred into hot water, it dissolves to make a solution.
Endothermic Reaction
A reaction that absorbs heat
Endothermic reactions cause the temperature to become cooler.
Evaporation
A physical change from a liquid to a gas
On a hot day, water droplets on a leaf evaporate into water vapour and rise into the air
Exothermic Reaction
A reaction that releases heat
Exothermic reactions cause the temperature to become hotter.
Fuel
Any substance that can burn
Fuels include paper, wood and petrol.
Gas
A substance with no fixed shape or volume
Particles in gases move quickly and spread apart.
Liquid
A substance with a fixed volume that flows and changes shape
Particles in liquids stay close together but move around each other freely.
Matter
Any substance that takes up space and has mass
Examples of matter include wood, water, air and your body.
Melting
A physical change from a solid to a liquid
If you heat chocolate on a stove it will melt, becoming liquid.
Mixing
A physical change where two or more substances are combined
Mixtures can be physically separated, e.g. by filtering a mixture of sand and water.
Particle
An atom or molecule
The particles in gold are gold atoms while in water they are water molecules.
Physical Change
A change in matter that does not form new substances
When you crush a can, it changes shape but is still the same substance.
Rusting
A chemical change where iron combines with oxygen and water
The new substance formed by this chemical change is iron oxide, or rust.
Solid
A substance with a fixed shape and volume
Particles in solids vibrate but stay in fixed positions.
Solidification
A physical change from a liquid to a solid
Ice is water that has solidified.
State of Matter
One of the forms that matter can take, such as solid, liquid or gas
The most familiar states of matter are solid, liquid and gas, but there are others.
Sublimation
A physical change from a solid to a gas
The dry ice in smoke machines sublimes into a gas at room temperature.
