1. CHEMICAL REACTIONS

2. The Atom Electron shell Negatively charged electrons Neutrons
Positively charged protons
NUCLEUS

3. The Atom
An atom has a neutral charge: number of protons = number of electrons
2 electrons can fit in the first shell of an atom & 8 in each subsequent shell
Atomic number (Z) = number of protons in an atom’s nucleus
Mass number (A) = number of protons + number of neutrons
Number of neutrons in an atom = mass number minus atomic number

4. The Periodic Table
Table created to group elements according to their properties
Vertical columns = groups
Horizontal rows = periods
Group number = number of electrons in outer shell
Period number = number of shells

5. The Periodic Table

6. The Periodic Table
Metals vs non-metals vs metalloids

7. The Periodic Table

8. Chemical & Physical Change
CHEMICAL CHANGE
PHYSICAL CHANGE
Produces a new substance
No new substances produced
Cannot be easily reversed
Can be easily reversed
Clues that a chemical reaction took place: light, change in temperature, colour change, gas production, smell
Involves a change in state or change in shape
Occurs when bonds between atoms break and new ones are formed
Caused by motion, temperature & pressure
E.g. cooking an egg, rusting of an iron pan, burning wood
E.g. crushing a can, melting an ice cube, boiling water

9. Chemical OR Physical? CHEMICAL CHEMICAL PHYSICAL PHYSICAL CHEMICAL
Burning paper
Baking a cake
Sweat cools you as it evaporates
Boiling water added to instant coffee
Photosynthesis
Margarine is melted
CHEMICAL
CHEMICAL
PHYSICAL
PHYSICAL
Burning paper – new substance produced (ashes)
Baking cake – materials coming together to form new substances
Sweat – water being changed from liquid to water vapour (change of state)
Water & coffee – could evaporate out
Photosynthesis – new products
Margarine – changing state of matter only
CHEMICAL
PHYSICAL

10. Chemical Reactions
Occur when bonds between atoms break and new ones are formed
Reactants  Products

11. Conservation of Mass Matter cannot be created or destroyed
Law of Conservation of Mass: mass of the reactants is equal to the mass of the products
i.e. all atoms present at the beginning of the reaction are present at the end of the reaction (and in the same proportion)

12. Endothermic & Exothermic Reactions
Absorb energy from surroundings
Release energy
More energy at end of reaction than at end
More energy at start of reaction than at end
E.g. instant ice packs, photosynthesis
E.g. portable hand warmers, airbags, dynamite

13. Acids & Bases: Characteristics
Corrosive
Can be corrosive
Sour taste
Bitter taste
Slippery or soapy to touch

14. Acids or Bases? Lemon – citric acid Vinegar – acetic acid
Gastric juices – acidic
Toothpaste – basic
Coffee – acidic
Baking soda - basic

15. Acid-Base Indicators
Added to a substance to determine if it is an acid or a base
Litmus:
Turns RED in an acid and BLUE in a base
Bromothymol blue:
Turns YELLOW in an acid and BLUISH-PURPLE in a base

16. The pH Scale Shows the relative strength of an acid or a base
pH of a substance can be determined using a universal indicator
Is a mixture of indicators that will change colour based on the strength of the acid or the base

17. The pH Scale 7 = neutral < 7 = acidic < 7 = basic
Strong acids have lower numbers
Strong bases have higher numbers

18. Neutralisation Acid + base  water + a salt
Sometimes a gas is also a product
Stop the effects of an acid by adding a base
Stop the effects of a base by adding an acid
Examples:
Relieve an ant sting by adding a weak base (e.g. sodium bicarbonate – baking soda)
Relieve a wasp sting by adding a weak acid (e.g. vinegar)

19. Neutralisation Examples
Certain plants grow better in acidic/basic soils
Add lime if soil too acidic
Add ammonium sulfate if soil is too basic

20. Neutralisation Examples
pH of a swimming pool should be between 7.2 – 7.8
If above 7.8, allows bacteria & microorganisms to grow  need to add an acid (e.g. sodium hydroxide)
If below 7.2, swimmers will get red & stinging eyes & the water may become corrosive  need to add a base (e.g. sodium bicarbonate)

21. Neutralisation Examples
If contents of stomach become too acidic (by eating too quickly or having too much of the wrong food) you will feel a burning sensation
Can be relieved by taking an antacid, which contain weak bases (e.g. aluminium hydroxide)
Burning sensation occurs due to the fact that acids are corrosive

22. Tooth Decay
When bacteria break down food acids are produced (especially sugary foods)
This acid can dissolve the enamel on your teeth
Bacteria can then get inside the tooth & cause tooth decay

23. Acids & Metals Acid + metal  a salt + hydrogen For example:
Sulfuric acid + copper  copper sulfate + hydrogen

24. Acid Rain As rain falls, water reacts with carbon dioxide in the air
This forms a weak acid
However, if there is a lot of sulfur dioxide and nitrogen oxide in the atmosphere, water reacts with these gases
This produces sulfuric acid & nitric acid  rain is more acidic than normal

25. Acid Rain
Sulfur dioxide & nitrogen oxide come from the burning of fossil fuels (natural gas, coal & oil)
Sulfur dioxide also comes from volcanoes

26. Acid Rain: Problems Eats into buildings & statues
Damages cells on leaves & affects water flow through plants
Makes plants more likely to be damaged by frost, fungi & disease

27. Acid Rain: Problems
Accumulates in lakes, ponds, streams, making waterway more acidic (pH decreases)
Some plants & animals cannot deal with these conditions and die
MORE ACIDIC

28. Acid Rain: Problems
Reacts with soil, releasing minerals (e.g. aluminium)
Aluminium is washed into the waterways
Poisons aquatic plants and animals

29. Acid Rain: Solutions Alternative ways of producing electricity
Using public transport or car pooling

30. Types of Chemical Reactions: Combustion
Combustion reaction: a substance (called a fuel) reacts with oxygen and heat is produced
Fuel + oxygen  carbon dioxide + water
Examples of fuels: natural gas, petrol, coal
Combustion can also produce dangerous gases (e.g. carbon monoxide)

31. Combustion Examples Gas stoves Cars Aeroplanes Electricity
Natural gas (methane) + oxygen  carbon dioxide + water
Cars
Fuel (octane) + oxygen  carbon dioxide + water
Aeroplanes
Fuel (kerosene) + oxygen  carbon dioxide + water
Electricity
Coal + oxygen  carbon dioxide + water

32. Types of Chemical Reactions: Respiration
Occurs in every cell in your body
Is how cells produce energy
Is a type of combustion reaction
Glucose + oxygen  carbon dioxide + water