Yr+9+Chemical+reactions

** YeaR 9 // chemical reactions // ** Go to the notes  https://www.tes.com/lessons/OC4zw9705Grb_Q/ || page 274 |||| **INQUIRY: INVESTIGATION 7.2 EXP: Conserve that mass!** Reactants, products, Conservation of mass page 258 |||| **INQUIRY: INVESTIGATION 7.3 EXP: Exothermic and endothermic processes** P279 Q13 or 14 || ** Words to Learn ** Exothermic Endothermic
 * __ Chemical Reactions -key concepts __**** – ** student guide 9 SCIENCE Name__
 * ** Key Concepts ** ||  ||||   ||
 * # 1. Patterns, order and organisation
 * 1) 2. Form and function
 * 2) 3. Stability and change
 * 3) 4. Matter and energy |||| NAME: ||
 * || ** Science Quest **
 * // TEXTBOOK //** |||| ** SCIENCE Quest ****// PRACTICALS / ACTIVITIES //** || ** SCIENCE Quest **
 * // HOMEWORK //** || ** OTHER ACTIVITIES/RESOURCES ** ||
 * 1 || **7 Chemical reactions** |||| **INQUIRY: INVESTIGATION 7.1 Reflecting on a burning candle p273**
 * The chemistry of eating** ||  || **Readiness Test Chapter 7**
 * 2 || **7.1 Rearrange those atoms**
 * Questions: p275 1-8** || 7.1 Combustion || ** Words to Learn **
 * Progress Test 7.1** Homework ||
 * 3 || **7.2 Matter and energy: Chemical reactions and energy**
 * Questions: p279 1-4, 8-10** || 7.2 Campsite chillout
 * EXTENSION:**

page 280 |||| **INQUIRY: INVESTIGATION 7.4 EXP:** Antacids in action The case of the unidentified solutions. (worksheet) || ** Words to Learn ** Play the **pH rainbow** in your eBookPLUS and drop liquids into their correct position on the pH scale. **int-0101** || page 285 See some of the destruction that acid rain has caused on Earth. Learn why acid rain is created and how we can stop it from occurring. **eles-0065**
 * Progress Test 7.2** Homework ||
 * 4 || **7.3 Acids and bases**
 * INQUIRY: INVESTIGATION 7.5 EXP:** Reaction of acids with metals
 * EXTRA EXP:** Making your own indicator
 * Questions: p284 3-6, 9,10,13,19,20** || 7.3 Acids and bases
 * Investigation;**
 * Interactivity**
 * 5 || **7.4 Acid rain**
 * //Science as a human endeavour//** |||| **INQUIRY: INVESTIGATION 7.6 Investigating acid rain**
 * eLesson**
 * The rain is burning!**
 * 7.6 EXP:** Investigating Acid Rain || **Questions: p269 1-5**

7.4 Acid rain

__Yr9 Acid rain task__ Assignment: prove to me you know all there is to know about acid rain || **Progress Test 7.4** Homework

Complete this as part of a pretest remember to put your class infront of your first name.

Access Code is 9ABHW

Test Link http://www.classroomclipboard.com/490625/Test/52C0DB1038B64DB597640C23FC220715 || page 287 |||| **Questions: p288 1-5, 6, 9**
 * 6 || **7.5 Combustion reactions**

[] || 7.5 Airship up in flames design an expt to measure the energy released when the following is combusted-tea light,wood, paper, metho, -weigh before and after keeping variables constant - use a variety of thermometers to measure the temp increase - eg digital, electronic infrared gun and glass || ** Words to Learn **
 * Combustion Reactions**

Homework
 * Progress Test 7.5**

some help for design your expt || Design and run your own game show. **pro-0107**
 * 7 || ** REVISION ** |||| **ICT Activity:** page 276
 * ProjectsPLUS**
 * ChemQuiz!**
 * Revision: p275 Q 1-3, 5-10, 13-18** || **Individual Pathways**
 * Activity 7.1** Revising chemicalreactions
 * Activity 7.2** Investigating chemicalreactions
 * Activity 7.3** Investigatingchemical reactionsfurther || Writing chemical formulae of compounds in symbol form ||

 =Class Notes Chemical reactions=

Burning match observation
When the match burnt we saw - smoke, colour change and heat was given off - these are indications that a chemical reaction has occurred. IN a chemical reaction the chemical that are mixed together at the start of the reaction are called the reactants. The things that are made are called the products.

The law of conservation of mass
says that matter can neither be created nor destroyed in a chemical reaction. the elements are rearranged to form new products. From this law we can also say that the atoms of elements that form the product of a reaction must be found as atoms of elements on the reactant side of the equation

Conservation of Mass Prac report
1. draw the apparatus label all relevant parts 2. initial weight of reactants - record in results 3. weight after reaction - record in results
 * Aim**
 * Method**

Observations 1. 2. 3. etc
 * Results**

Data


 * Conclusion**

If the masses are different suggest a reason why. If the masses are the same suggest a reason why.

End of prac report _

__**Example**__ __alka seltza tablets and the water were the reactants. when we weighed them before they reacted together they all weighed 122g. When we mixed them together lots of gas bubbled out of the water. This gas was one of the products. The mass of the all the products were 122g.__ __The mass had not changed - this proved the law of conservation of mass.__

In Chemistry we often write a word equation or molecular formula equation to explain what has happened in the chemical reaction. These equations show how the reactants have recombined to form new products.
 * Writing Equations for reactions**

reactant is a product is

A Chemical Reaction occurs when two or more reactants react to produce one or more products. This may cause bubbles to form ( gas is given off), temperature change (exothermic or endothermic) change of colour or a new product may appear.

A chemical reaction is described by the following word equation:

=Exothermic reactions and endothermic reactions= Exothermic reactions give out heat (or sound or light) Energy (or sometimes all of these - eg an explosion. Exothermic reactions make the thermometers go up. Eg Acid and magnesium. The temp of the soultion went up - exothermic.

Endothermic reactions take in energy making their surroundings colder. The thermometer goes down. Eg Potassium Chloride and water - the whole testtube gets cold- the thermometre went down. this is endothermic

An airbag explodes -Endo or exo?

=Acids and Bases=

Acids are chemicals that are sour and corrosive. They have a pH of less than 7. they are used in industry, they react with metals to produce hydrogen gas and a salt. Bases are slippery and have a pH of more than 7 Water is nether an acid or a base - it is neutral and has a pH of 7 Acids and Bases reactions An Acid + Base --> Salt + Water

Common acids and bases||~ Acid
 * ~ Uses ||
 * Hydrochloric acid || * To clean the surface of iron during its manufacture
 * Food processing ||
 * Nitric acid || * The manufacture of fertilisers, dyes, drugs and explosives ||
 * Sulfuric acid || * The manufacture of fertilisers, plastics, paints, drugs, detergents and paper
 * Petroleum refining and metallurgy ||
 * Citric acid || * Present in citrus fruits such as oranges and lemons
 * Used in the food industry and the manufacture of some pharmaceuticals ||
 * Carbonic acid || * Formed when carbon dioxide gas dissolves in water; present in fizzy drinks ||
 * Acetic acid || * Found in vinegar
 * The production of other chemicals, including aspirin ||

> || =** pH Scale and determining Acids and Bases **=
 * ~ Base ||~ Uses ||
 * Sodium hydroxide (caustic soda) || * The manufacture of soap
 * As a cleaning agent ||
 * Ammonia || * The manufacture of fertilisers and in cleaning agents ||
 * Sodium bicarbonate || * To make cakes rise when they cook

This scale tells us the strength of the acid or base. The scale goes from 0 to 14. Any compound registering below 7

Is called an acid. Weak acids have a pH of 4 to 6 ( vinegar). Strong acids have a pH of 0 to 3 (HCl or sulphuric or nitric acids).

Compounds with a pH of 8 to 10 are basic or alkaline eg blood or soda water, some detergents.

Compounds with a pH of 11 to 14 are strong bases egs are ammonium, dishwashing powder, NaOH. Water is neutral and has a pH of 7. Indicators An indicator will change colour in the presence of an acid and will change to a different colour in the presence of a base. Universal indicator goes red in an acid, green in water (neutral) purple in base. It also changes to a yellow in a weak acid and a blue/ green in a weak base.

=ACID + ANTACID PRACTICAL= DISCUSS AND EXPLAIN 1. What was the mass of the antacid powder? 1g 2. What colour change occurs when the methyl orange indicator is in the acid? red in acid and goes orange when no acid is there. 3. By subtraction, calculate the mass of antacid used to neutralise 50 mL of dilute hydrochloric acid. =1g 4. How does your result agree with other groups in your class? Suggest reasons for the similarities or differences between your results. Different colours of orange were expected by the different groups 5. Use your results to calculate how much antacid you would need to neutralise 500 mL of dilute hydrochloric acid. If 1g is needed for 50 mLs then _10g is needed for 500mL The reaction was a neutralisation reaction. Acid + base > salt + water 2HCl + Mg(OH)2 --> Mg Cl2 + 2 H2O The reaction that caused the bubbles was Acid + carbonate > salt + water + carbon dioxide

example Calcium carbonate + Hydrochloric acid -> Calcium Chloride + carbon dioxide + water

INQUIRY: INVESTIGATION 7.5 =Reaction of acids with metals= When an acid reacts with a metal, a salt is formed and hydrogen gas is given off. You can test for hydrogen gas by holding a lighted match at the mouth of the test tube. If the gas is hydrogen, it will explode and make a ‘pop’ sound. • Place a small piece of one of the metals in a test tube. • Add the acid to the test tube to a depth of 1 cm. • Observe the chemical reaction. • Test for hydrogen gas by holding a rubber stopper over the end of the test tube for a few seconds and then placing a lighted match at the mouth of the test tube. CAUTION: Do not push the stopper into the test tube firmly. Just hold it in the top of the test tube for a few seconds. • Record your observations. • Repeat the test with other metals. DISCUSS AND EXPLAIN 1. When zinc metal reacts with hydrochloric acid, zinc chloride and hydrogen gas are formed. Write a word equation for this reaction.

ZInc + Hydrochloric acid > Zinc Chloride + Hydrogen gas

1. When the lighted match produces a ‘pop', the hydrogen gas is reacting with the oxygen in the air to form water. You may have noticed the water form at the top of the test tube after you performed the match test. Write a word equation for this chemical reaction.

Hydrogen gas + Oxygen gas -> water

Combustion Reactions The General equations for a combustion reaction is Organic material + oxygen --> water + Carbon Dioxide

eg Methane gas + oxygen > water + carbon dioxide

=Testing the acidity of household substances=

Method
1 Test with red litmus by adding one drop of substance and record 2 Test with blue litmus by adding one drop of substance and record 3 Test with universal indicator by adding one drop of indicator to 3 mL of substance record the colour. NB solids will need to be dissolved at the ratio of one grain of rice size to 3 mL of water.

Results
Conclusion The following were acidic; Lemonade, lemon juice, vinegar and of these lemonade was not as acidic as the others according to our universal indicator results red being more acidic than orange or yellow. The following were basic; Sodium bicarbonate, detergent - The following were neutral; water, salt
 * Substance || Red litmus turned || Blue Litmus turned || Universal indicator turned ||
 * Water || nc || nc || green ||
 * Lemonade || r || r || orange ||
 * Lemon Juice || r || r || red ||
 * Vinegar || r || r || red ||
 * Salt || nc || nc || green ||
 * Sodium Bicarbonate || b || nc || blue/aqua ||
 * detergent || b || r || blue/purple ||

RED litmus always turns blue in a base or alkali and will turn back to red in an acid BLUE litmus always turns red in an acid and will turn back to bue if dipped into a base or alkali UNIVERSAL INDICATOR gives us a range of colours from RED (strong acid) to orange and yellow (weak acid) to GREEN (neutral) to aqua for weak bases to blue and purple for strong bases and alkalis

=Designing an expt to measure the energy output of fuels=

Background
When fuels are burnt an exothermic reaction occurs. A general form of this reaction can be written as; Fuel + oxygen --> water + carbon dioxide + heat energy

Heat can change the temperature of water. The energy required to heat 1 gram pf water 1 degree celsius is 4.2 Joule. We call this the specific heat of water.

Therefore heat energy out put can be calculated by Heat Energy = Mass of water X 4.2 X Temp change.


 * Aim**


 * Hypothesis**

1. variables to keep constant are; height of fuel from the water, mass of water ,
 * Method**

Results = 1400 Joules per 0.5 g ||
 * Fuel || Variable || Before || After || Change || Calculations of Energy output per gram ||
 * candle || mass of water ||  ||   ||   ||   ||
 * || temperature ||  ||   ||   ||   ||
 * || mass ||  ||   ||   ||   ||
 * wood || mass of water ||  ||   ||   ||   ||
 * || temp ||  ||   ||   ||   ||
 * || mass ||  ||   ||   ||   ||
 * paper || mass of water || 10 || 10 || 0 || HeatEnergy = mass of water x 4.2 x temp change ||
 * || temp || 15 || 40 || 25 || Heat energy = 10 x 4.2 x 25
 * || mass || 10g || 9.5g || 0.5g || heat energy per gram =2800/g ||

=Extra notes Beyond the level=

// Solution means in water = (aq) //
 * Writing Chemical Formula of__ compounds __ **[[file:1b. IONIC FORMULA.doc]]


 * Step 1. Determine the symbol and charge of each ion (the numerals in represent the ion’s charge) but write the cation (+ ions) before the non-metal anion(s) (- ions) except for substances with acetate.**


 * || = CATIONS = ||  ||   || ** ANIONS ** ||   ||
 * ** 1+ ** || ** 2+ ** || ** 3+ ** || ** 1- ** || ** 2- ** || ** 3- ** ||
 * Ammonium NH 4 + || Barium Ba 2+ || Aluminium Al 3+ || Bicarbonate HCO 3 - || Carbonate CO 3 2- || Nitride N 3- ||
 * Cuprous (I) Cu + || Beryllium Be 2+ || Chromium Cr 3+ || Bromide Br - || Chromate CrO4 2- || Phosphate PO 4 3- ||
 * Hydrogen H + || Calcium Ca 2+ || Ferric (III) Fe 3+ || Chloride Cl - || Dichromate Cr 2 O 7 2- || Phosphide P 3- ||
 * Lithium Li + || Copper (II) Cu 2+ ||  || Chlorate ClO 3 - || Zincate Zn(OH) 4 2- ||   ||
 * Potassium K + || Iron (II) Fe 2+ ||  || Permanganate MnO 4 - || Silicate SiO 3 2- ||   ||
 * Silver Ag + || Lead (II) Pb 2+ ||  || Acetate CH3COO - || Oxide O 2- ||   ||
 * Sodium Na + || Magnesium Mg 2+ ||  || Fluoride F - || Peroxide O 2 2- ||   ||
 * || Strontium Sr 2+ ||  || Hydride H - || Sulfate SO 4 2- ||   ||
 * || Tin Sn 2+ ||  || Hydroxide OH - || Sulfide S 2- ||   ||
 * || Zinc Zn 2+ ||  || Iodide I - || Sulfite SO 3 2- ||   ||
 * || Mercury Hg 2+ ||  || Nitrate NO 3 - || Thiosulfate S 2 O 3 2- ||   ||
 * ||  ||   || Nitrite NO 2 - ||   ||   ||

eg. Al3+Cl-, Charge number of Al is a 3 and the charge number of Cl is a 1 so Al1Cl3 but write it as AlCl3 eg. Pb2+NO3-. Charge number on Pb is a 2, and NO3 is only a 1 so Pb1(NO3)2 but write it as Pb(NO3)2.
 * Step 2. To write a chemical formula, write __ONE__ of each ion & balance the ion charges so the total is 0 by writing the required coefficient to the __bottom right of the ion__ ** . **For multiples of an atom group, use .**

Another way to do this is to remember the hook and eye model Remember the cations have hooks - the anions have eyes. draw the cations with their hooks and then join these with the eyes of the anions. Keep adding cations or anions until there are no empty hooks or eyes. This will show the number of cations and anions that will combine to form the compound.

Eg.



Class notes

Physical or Chemical change

Expt

Results

Hydrogen gas given off || Chemical Change ||
 * Chemical || Observation || RESULTS ||
 * CaCO3 || White powder no change || NC ||
 * Mg + HNO3 || Bubbled and cloudy
 * Pb(NO3)2 + KI || Turned yellow || Chemical Change ||
 * HNO3 + NaOH || Got warmer || Chemical Change ||
 * CuSO4 + Mg || Mg Turned Black, Cu ions attached to the Mg || Chemical Change ||

We know a chemical change has occurred if we see one or more of the following;

Colour change

Gas or bubbles given off

Change in Temperature – (getting hotter or colder)

New product formed – eg a precipitate or metal deposit

Write an outline of the light sticks experiment p 54


 * Chemiluminesence ** – Chemical change that produces light as the result of a chemical reaction.

If it was put into hot water – it got brighter because the molecules sped up and bumped into lots of other

molecules make a stronger reaction. The cold water slowed the reaction down and so less light was

emitted. Animal can produce this as well and we call this bioluminescence.


 * Solubility **

When a salt dissolves in water it is said to dissociate – this means the ions that make up the salt will float freely in the water as

Cations or anions. Eg NaCl - à Na + and Cl- ions.


 * Characteristics of chemical classes **


 * 1) Acids – All acids contain hydrogen and usually a non metal or a non metal oxide. (Phosphate – P and O = PO4 3- this makes phosphoric acid)

H3PO4 Other examples of acids are Sulphuric acid H2SO4, Nitric acid HNO3, Hydrochloric acid HCl, Hydrofluoric Acid HF, Vinegar or acetic acid or

Ethanoic acid CH3COOH


 * 1) Bases or Alkalis – These contain a metal combined with a hydroxide group -(OH) Examples of these are MgOH2,

AlOH3, ZnOH2, NaOH


 * 1) Salts – This is a general name for the substance formed by an ionic bond between a metal and a non metal

Example MgCl2, NaCl, CaCl2, MgSO4

4.The nitrates – these are compounds joined by an ionic bond between a metal and the nitrate complex anion. Eg NaNO3, Ca(NO3)2


 * 1) Sulfates – these are compounds joined by an ionic bond between a metal and the sulfate complex anion. Eg MgSO4, CuSO4


 * Types of reactions **

Neutralisation – This is a reaction between a acid and a base (or alkali) –When an acid reacts with a base they neutralise each other.

The products formed are a salt and water.

Do these

Hydrochloric acid + sodium Hydroxide --- à

Nitric acid + Calcium Hydroxide --->

Sulfuric acid + potassium hydroxide - à


 * Precipitation reactions **

These are any reaction that forms a solid that might continue to float in the solution – The best example is

KI (aq) + Pb (NO 3 ) 2 (aq) ---> KNO 3 (aq) + PbI 2 (s) This makes the bright yellow specks that we made in our experiment.

The subscripts that are in brackets behind a chemical formula indicates the state of the chemical in the reaction.

(s) means solid

(l) means liquid

(g) means gas

(aq) means aqueous – aqueous means dissolved in water generally resulting in ions floating in the water.


 * Combustion Reactions **

This type of reaction always combines oxygen with another compound or element to make an oxide ( ie oxygen combined

With a metal or nonmetal like carbon)

Eg Methane + oxygen à carbon dioxide and water

Eg2 Magnesium + oxygen à magnesium oxide


 * pH Scale and determining Acids and Bases **

This scale tells us the strength of the acid or base. The scale goes from 0 to 14. Any compound registering below 7

Is called an acid. Weak acids have a pH of 4 to 6 ( vinegar). Strong acids have a pH of 0 to 3 (HCl or sulphuric or nitric acids).

Compounds with a pH of 8 to 10 are basic or alkaline eg blood or soda water, some detergents.

Compounds with a pH of 11 to 14 are strong bases egs are ammonium, dishwashing powder, NaOH.

Water is neutral and has a pH of 7.

Different bonds

Ionic bonds – these are between metal and non metals – found in salts. This is where one element donates an electron to

Another element eg NaCl

Covalent bonds – this is where two or more non metals share electrons eg Carbon dioxide, water,

Metallic bonds – are the ways metal atoms join together to make a slab of metal. They are described as a lattice of cations

Floating in a sea of electrons.