1. TWO TYPES OF CHANGES Physical Changes Chemical Changes
A change that alters a physical property of a substance (eg shape, state, temperature) but doesn’t make a new substance.
A change that forms one or more new substances
Usually reversible – can get the original substances back easily
Usually irreversible – cannot get the original substances back.
Examples – cutting paper, freezing water to form ice, dissolving sugar in water
Examples – cooking an egg, burning paper, baking a cake

2. CHEMICAL REACTIONS
Chemical reaction: a process where one or more chemical substances undergo a chemical change to form a new substance
Signs of a chemical reaction
A new substance is formed
A gas a released (bubbles formed)
A solid forms (also called a precipitate)
A rise or drop in temperature
Colour is permanently changed

3. CHEMICAL REACTIONS
Reactant: a chemical substance that is present at the start of a chemical reaction (what we start with) Product: a chemical substance that is formed as a result of a chemical reaction (what we end up with)

4. CHEMICAL REACTIONS
We can describe what is happening using a chemical equation.
Chemical equations are always written in the form: reactants → products
We can write chemical equations using:
Words (eg hydrogen + oxygen → water)
Chemical formula (eg H2 + O2 → H2O)

5. WRITING WORD EQUATIONS
Sodium reacts with iron (III) chloride to form sodium chloride and iron.
When propanol is burnt in oxygen gas, carbon dioxide and water are formed.
Hydrogen peroxide splits to form water and oxygen gas.
A piece of aluminium was dropped into hydrochloric acid. The aluminium dissolved and reacted to form aluminium chloride. As it did so, hydrogen gas bubbled to the surface.

6. QUICK QUIZ Write the definition of a chemical reaction.
Write the definition of reactant and product.
Which of the following signs shows that a chemical change has occurred during a reaction?
The reaction is reversible
There has been a change in state (eg solid, liquid or gas).
There is a permanent colour change.
There has been a change in shape

7. DUE: Tomorrow (Friday Lesson 6)
PRACTICAL REPORT
For this practical report, you need to include:
Title
Introduction (include aim, hypothesis and state independent, dependent and control variables)
Materials
Method (written in numbered steps, include a diagram)
Results
Discussion (include your observations here)
Conclusion
For more information about what to include in these sections, refer to the “Writing a Scientific Report” sheet
DUE: Tomorrow (Friday Lesson 6)

8. What results were we expecting from the practical?
Law of Conservation of Mass: mass is neither created nor destroyed during a chemical reaction
(in other words, you have to finish with the same number and type of atoms that you started with … the mass at the beginning should be the same as the mass at the end)
CaCO3 + HCl → CaCl2 + H2O + CO2
In the beaker, where did the CO2 go? What should have happened to the weight?
In the flask, where did the CO2 go? What should have happened to the weight?

9. PRACTICAL REPORT CHECKLIST
Title
Introduction – aim, hypothesis, independent variable, dependent variable, control variables, word and formula equation of the reaction.
Materials – a list of all equipment and chemicals you used.
Method – numbered steps of what you did during the practical, diagram of the prac set up.
Results – could be written neatly or in a table. DO NOT need a graph for this prac.
Discussion – what observations did you have during the practical, describe your results in sentence form, did your results support your hypothesis, were the results you obtained what you were expecting to get, could there be any sources of error in the practical (human or equipment), what could you do next time to improve the practical.
Conclusion – Short! A quick summary – was your hypothesis supported or rejected, what did you find out during the practical?

10. ACIDS
Acid: a substance that releases hydrogen ions (H+) into a solution.
Properties of acids
Contain hydrogen atoms
Turn blue litmus paper red
Taste sour
Corrosive

11. BASES
Base: a substance that releases hydroxide ions (OH-) into a solution.
Properties of bases
Bases are commonly found in cleaning products.
Turn red litmus paper blue
Taste bitter
Feel slippery

12. pH SCALE AND INDICATORS
pH scale: a scale from 0-14 that shows how acidic or basic a substance is.
Acid: pH < 7
Neutral: pH = 7
Base: pH > 7
To test to pH of a substance we can use an indicator.
An indicator is a substance that changes colour when an acid or base is present.

13. (Alkaline = basic)

14. REACTIONS WITH ACIDS All acids react in predictable ways:
Acid + Metal → Salt + Hydrogen gas
Acid + Carbonate → Salt + Water + Carbon Dioxide
Open textbook to Page

15. QUICK QUIZ
Use the pH scale to match the pH measurements with the solutions below:
pH 4
Neutral solution
pH 7
Moderately acidic solution
pH 1
Moderately basic solution
pH 8
Very acidic solution
pH 10
Slightly basic solution

16. IMPORTANCE OF pH

17. PHOTOSYNTHESIS
Plants use the energy in sunlight to produce food in the form of a simple sugar called glucose.
Photosynthesis can be summarized by the equation:
Carbon dioxide + Water Glucose + Oxygen
Sunlight and chlorophyll are written over the arrow to show that they are necessary for the reaction to occur, but are not used up in the reaction.
Sunlight
Chlorophyll

18. PHOTOSYNTHESIS
Plant cells contain structures called chloroplasts. These contain chlorophyll, which gives plants their green colour.
Chlorophyll absorbs energy from the sun to start the process of photosynthesis.

19. PHOTOSYNTHESIS
For photosynthesis to occur, a plant needs sunlight, chlorophyll, carbon dioxide and water.
Sunlight comes from the sun
Carbon dioxide is absorbed from the atmosphere through tiny openings in the leaves called stomata.
Water is carried from the plant’s roots into the leaves.
Chlorophyll is found in the chloroplasts.

20. Quick Quiz What is the definition of an acid?
What is the definition of a base?
If you mix an acid and a base together, what do you think would be produced? Hint: think about what acids and bases release into a solution.

21. NEUTRALISATION REACTIONS
Neutralisation Reaction: a reaction where an acid and a base cancel each other out to form a salt and a water.
Acid + Base  Salt + Water
The H+ ions from the acid combine with the OH- ions from the base to form water. The ions left over combine to form a salt.

23. HOW TO WRITE YOUR PRACTICAL REPORT
Your report MUST have the following headings: introduction, aim, hypothesis, variables, safety, materials, method, results, discussion, conclusion.

24. HOW TO WRITE YOUR PRACTICAL REPORT
Aim: explains the purpose of the practical – it is not a question.
Variables: are factors in an experiment that could vary.
Independent variable – the variable that you change on purpose.
Dependent variable – the variable that you measure
Control variables – the variables that must be kept the same during the entire experiment.

25. HOW TO WRITE YOUR PRACTICAL REPORT
Hypothesis: a prediction about what you think will happen. A hypothesis should always be written as a if/then statement: If …(change independent variable)… , then .. (what happens to dependent variable)…

26. HOW TO WRITE YOUR PRACTICAL REPORT
Materials: a list of everything that you used – all equipment and chemicals.
Be specific about the concentration and amount of chemicals that you used and the sizes of the equipment you used.
Method: a step-by-step description of what you did. Must be in past tense.
Instead of “we put the acid in the flask and then dropped in a few drops of methyl orange indicator”, say “A flask was filled with 50 mL of hydrochloric acid and 3-4 drops of methyl orange indicator were added.”
Include a diagram of your practical set-up

27. HOW TO WRITE YOUR PRACTICAL REPORT
Results: this is where you record/display the data that was collected during the practical.
Include any observations that you recorded during the practical
Display your data in a table
Can your data be displayed in a graph format?

28. PRACTICAL REPORT
Aim: purpose of the practical – this is not a question. Hypothesis: If …(change independent variable), then .. (what happens to dependent variable)
Title
Introduction – aim, hypothesis, independent variable, dependent variable, control variables, word and formula equation of the reaction.
Materials – a list of all equipment and chemicals you used.
Method – numbered steps of what you did during the practical, diagram of the prac set up.
Results – could be written neatly or in a table. DO NOT need a graph for this prac.
Discussion – what observations did you have during the practical, describe your results in sentence form, did your results support your hypothesis, were the results you obtained what you were expecting to get, could there be any sources of error in the practical (human or equipment), what could you do next time to improve the practical.
Conclusion – Short! A quick summary – was your hypothesis supported or rejected, what did you find out during the practical?