Week 5 - Chemical Sciences Part 2

Question 1

What is a physical property?

Answer 1

Property that can be observed and measured without changing the composition

Question 2

Chemical properties

Answer 2

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!

Question 3

Changing properties and energy

Answer 3

Materials undergo changes which can be either physical or chemical

These changes are always associated with energy - energy is absorbed or released

Question 4

What is a physical change?

Answer 4

Wood being cut

Same material not a new substance

Reversible because no new substance is formed

Doesn’t change the substance - only visible qualities

Question 5

Chemical change?

Answer 5

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

Question 6

How to tell if it is a chemical change

Answer 6

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

Question 7

What are chemical changes in everyday life?

Answer 7

Cooking
Burning
Rusting
Souring
Photosynthesis 
Respiration

Question 8

A reversible change?

Answer 8

Can be undone - can be converted back without making new material

Eg water or chocolate

Question 9

Irreversible change

Answer 9

Some cannot be reversed

Eg burnt wood cannot form same piece of wood again

Question 10

What are three types of mixtures

Answer 10

Solution

Colloid

Suspension

Question 11

Solution

Answer 11

Small suspension of molecules - one is blended with another

Question 12

Colloid

Answer 12

Two materials that don’t dissolve and make the particles so small they can’t seperate

Question 13

Suspension

Answer 13

Big chunks and mix with something else - particles of one suspended in another

Question 14

What determines the type of mixture it is classified as?

Answer 14

Size of the particles

Question 15

Everything around us is made of matter - what happens when we mis and un-mix things chemically?

Answer 15

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

Question 16

What is a pure substance?

Answer 16

Contain particles that are all exactly the same

There are 2 different types of pure substances- molecules and compounds

Question 17

What are mixtures?

Answer 17

Impure substances

Made up of several different elements or compounds together

There are herterogeneous (different) and homogeneous (same) mixtures

Question 18

Homogeneous mixture

Answer 18

All substances are evenly distributed throughout the mixture

Repeated pattern and atomic level

It is uniform throughout

Question 19

Heterogeneous mixture

Answer 19

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

Question 20

What is a solution made of

Answer 20

Solvent - often liquid

Solute - often what dissolves

Question 21

What is an alloy?

Answer 21

Mixture of elements that has the characteristics of a metal

At least one element is metal