Week 5 - Chemical Sciences Part 2 Flashcards
What is a physical property?
Property that can be observed and measured without changing the composition
Chemical properties
A property that can be observed by changing the composition of the material
Eg the ability to burn, decompose, ferment, rust, react with etc.
Must do something to see change!
Changing properties and energy
Materials undergo changes which can be either physical or chemical
These changes are always associated with energy - energy is absorbed or released
What is a physical change?
Wood being cut
Same material not a new substance
Reversible because no new substance is formed
Doesn’t change the substance - only visible qualities
Chemical change?
There is a change in substance - something is added
Irreversible because they form new compounds
Chemical change is a reactor
Atoms in one or more chemicals split up and join together in new ways
How to tell if it is a chemical change
Formation of a product - solid or gas
One of the reactants may be used up
The colour may change
Bubbles of gas may appear
Heat and light are produced
What are chemical changes in everyday life?
Cooking Burning Rusting Souring Photosynthesis Respiration
A reversible change?
Can be undone - can be converted back without making new material
Eg water or chocolate
Irreversible change
Some cannot be reversed
Eg burnt wood cannot form same piece of wood again
What are three types of mixtures
Solution
Colloid
Suspension
Solution
Small suspension of molecules - one is blended with another
Colloid
Two materials that don’t dissolve and make the particles so small they can’t seperate
Suspension
Big chunks and mix with something else - particles of one suspended in another
What determines the type of mixture it is classified as?
Size of the particles
Everything around us is made of matter - what happens when we mis and un-mix things chemically?
Molecules are building blocks for things
They can be put together in different ways
Everything is made up of atoms
Combine - recombine and seperate
Things are essentially made of the same things but put together differently
** post humanistic- how things are interconnected
What is a pure substance?
Contain particles that are all exactly the same
There are 2 different types of pure substances- molecules and compounds
What are mixtures?
Impure substances
Made up of several different elements or compounds together
There are herterogeneous (different) and homogeneous (same) mixtures
Homogeneous mixture
All substances are evenly distributed throughout the mixture
Repeated pattern and atomic level
It is uniform throughout
Heterogeneous mixture
Substances are not evenly distributed
Chocolate chip cookies, pizza etc.
Each quarter is different, random and no consistent pattern - at atomic level
It is not uniform throughout
What is a solution made of
Solvent - often liquid
Solute - often what dissolves
What is an alloy?
Mixture of elements that has the characteristics of a metal
At least one element is metal
