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Year 7 Science: Chemical Change

Homework may be marked on Firefly – check your feedback and make corrections to your work! This is your responsibility!

Revision Checklist

I can name all the parts of a Bunsen Burner and I can describe how to light a Bunsen burner

I know the difference between the safety flame, medium flame and roaring flames (colour, temperature, when to use them and how to create them)

I can draw 2D pencil diagrams do show the following equipment being used: heat proof mat, beaker, boiling tube, delivery tube, clamp, boss, clamp stand

I can describe the appearance of copper carbonate, copper oxide, copper sulphate (with and without water)

I know what happens if I heat hydrated copper sulphate (hydrated = contains water)

I can describe the tests for oxygen, hydrogen and carbon dioxide

I can explain why sometimes chemical reactions go down in mass

I can explain why sometimes chemical reactions go up in mass

I can describe the differences between chemical reactions and physical changes

Word MeaningIndependent variable

The thing that you change in an experiment

Dependent variable

The thing that you measure and write in your results table

Control variables

Things that you need to keep the same to make your test fair

Reliable Trustworthy results. You can make your experiment more reliable by repeating it and taking an average of the results, or by comparing your results with someone else.

Fair test An experiment where you only change one thing (the independent variable)

Laboratory Safety

Hazard Symbols

Grange School Laboratory Rules1). You must not enter a laboratory unless told to do so by a member of staff.

2). You must wear a laboratory coat and safety glasses/goggles for practical work when told to do so. This includes clearing away when finished.

3). You must not touch apparatus or chemicals until told to do so by a member of staff. You must follow all instructions precisely. Do not make up your own experiments.

4). Long hair must be tied back during practical work. This is especially important when using Bunsen burners.

5). Report ALL accidents (including burns, cuts, bites, breakages and spillages) to the teacher.

6). Use the correct waste disposal container: there are special bins for broken glass and animal and plant waste. Always use a dustpan and brush to clear up broken glass. Never put solid waste into the sinks.

7). When working with liquids you must stand up for practical work. This means you can move out of the way quickly if there is a spillage.

8). Do not eat or drink in the laboratory. Nothing must be put into your mouth. This includes parts of plants and pens/pencils (which might have picked up a toxic substance from the bench).

9). If any chemicals get onto your hands or any other parts of the body, wash them off. You must always wash your hands after any practical work that involves chemicals, animal, plants or micro-organisms.

10). Never bring any chemicals or animals (dead or alive) into the laboratory unless specifically asked to by your teacher.

11). All gangways must be kept clear of obstructions. Bags should be placed either under the benches or on side benches if they are not in use. Stools should be pushed under the benches during practical work.

12). You must clear up any small splashes. Larger spillages must be reported to the teacher.

13) Do not run in a laboratory.

Questions: Safety

The Bunsen Burner

A Bunsen burner is used for:

1) H _ _ _ _ _ _

2) S _ _ _ _ _ _ _ _ _ _ _

3) B _ _ _ _ _ _

It is connected to the gas (m _ _ _ _ _ _) supply with a rubber tube. You light a Bunsen with a s _ _ _ _ _ with the air hole c _ _ _ _ _ and the g _ _ t _ _ half open.

Flame Type Air Hole Colour of Flame

Bunsen Burner LicenceName of examiner: ____________________________ Number of tasks passed: ______________________________ /27

Description of task - the examiner reads this task out

Marking points Number of marks

1 “Prepare yourself and your desk for using a Bunsen burner safely”

o Clear workspace and stools tucked under desks (must remain standing throughout)

o Hair tied back. Goggles on. o Lab coat on.o Books and pencil cases organised

2 “Collect a Bunsen burner, splint and heatproof mat and leave them on your desk ready for checking”

o The equipment is collected and carried calmly. o The correct equipment is collected.

3 “Show me the: collar, air-hole, chimney, rubber hose and gas tap and check your Bunsen is safe to use”

o Collar and air hole named correctly.o Chimney, gas tap and rubber hose named correctlyo Checks tubing is not cracked.o Checks collar moves. o Checks barrel is clear.

4 “Set-up the Bunsen burner on a heatproof mat, ready to be lit.”

o Bunsen burner is placed on centre of the heatproof mat.

o The air hole is closed. o Rubber tubing is connected to gas tap and is not

twisted. 5 “Light the Bunsen burner using a

splint. “o The student lights a splint using the Bunsen burner

on the teacher’s desk. o The splint is carried calmly and safely back to the

student desk, using a hand to shield the flame. o The air hole is closed. o The gas is quickly turned on.o The lit splint is safely dabbed out and placed on the

heatproof mat to put it out.6 “Change the safety flame to the

blue heating flame and then a roaring flame and then back to a safety flame”

o The student moves the collar to open the air hole partially, then fully, then closed again

7 “Tell me difference between the 3 types of flame in terms of when you use them, temperature and colour”

o Knows safety flame is the coolest, it is orange and it is used when the Bunsen isn’t being used to keep the flame visible

o Knows the blue flame is medium temperature, it is visible and blue and is used to heat things

o Knows the roaring flame is the hottest, it is invisible and it is used to heat things strongly.

8 “Turn off your Bunsen burner and (tell me how you would) pack the equipment away. “

o The gas tap is switched off. o Time is given to allow the Bunsen burner to cool

down.o The splint is cooled under the tap and put in the bin.o Equipment is returned to the correct location.

Laboratory Equipment

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Chemical and Physical ChangesSome changes are called p _ _ _ _ _ _ _ changes. These changes do not make new c _ _ _ _ _ _ _ _

and you can un-do the change. They are r _ _ _ _ _ _ _ _ _.

Some changes are called c _ _ _ _ _ _ _ changes. These changes do make new c _ _ _ _ _ _ _ _

and you cannot un-do the change. They are i _ _ _ _ _ _ _ _ _ _ _.

Physical change Chemical change / Chemical reaction

What does it mean?

Examples

Is a brand new chemical made?

Is it reversible?

Chemical and Physical Changes

Change Is it a physical or a chemical change?

Why do you think this?

Frying an egg

Squashing plasticene

Melting ice

Heating copper sulfate

Mixing salt and sand

Heating magnesium in a Bunsen flame

Heating copper carbonate

Questions: Chemical & Physical Changes

Practical: Chemical ChangesMetal Appearance at the start What happened during the

reactionAppearance after the

reactionCopper carbonate

Copper sulphate

Magnesium

Observing Chemical ReactionsObservations could be: Sight (colour changes, fizzing), Sounds (fizzing, a pop), Smell (do not put test tube under your nose, waft the smell towards you), Touch (feel the outside of the test tube carefully for a temperature rise or fall)

If you don’t see anything, say “No visible change” not “Nothing happened”

Reaction At the start what did they look like? What did you observe happen?

Citric acid + Sodium carbonate solution

Ammonium chloride + distilled water

Magnesium + Hydrochloric acid

Potassium iodide + Lead nitrate (TOXIC!)

Sodium sulphate + Barium chloride

How can we tell a reaction has occurred?

Questions: Observing Chemical Reactions

Practical: Mass Change in a Chemical Reaction

For these experiments we need to use a _ _ _ _ _ _ _

Describe the appearance of copper carbonate _______________________________________

When copper carbonate is heated a new chemical is formed called _______________________

Mass of empty boiling tube /g

Mass of boiling tube and copper carbonate /g

Mass of boiling tube and copper oxide after heating /g

Calculate the mass of the copper carbonate before heating

Calculate the mass of the copper oxide after heating

The mass of the chemical decreased. This is because a gas was released into the air. This gas is

called __________________________________. We know this because __________________

_____________________________________________________________________________

Write a word equation for this chemical reaction

Practical: Mass Change in a Chemical Reaction

Heating zinc foil

Mass of zinc foil at start /g

Mass of zinc foil after 30 seconds of heating /g

What happened to the mass of the zinc?

This is because…

A word equation for this reaction:

Summary

Sometimes mass i _ _ _ _ _ _ _ during a chemical reaction. This is because a g _ _ from the air has j _ _ _ _ _ the start chemical.

Sometimes mass d _ _ _ _ _ _ _ _ during a chemical reaction. This is because a g _ _ is given off from the start chemical.

If the reaction is done in a s _ _ _ _ _ environment, the mass does not change because the gases are trapped.

Mass cannot be c _ _ _ _ _ _ or d _ _ _ _ _ _ _!

Questions: Mass Change:

Mass Change Task:

Gas Collection

Collecting gases over waterThe gas produced in a reaction is bubbled through a trough of water and into an upturned test tube filled with water. The bubbles of gas collect in the top of the test tube and displace (push out) the water out of the bottom. If enough gas is produced it completely replaces the water in the test tube. You can then put a bung in the test tube which is then removed from the trough of water and turned the right way up.

This works well for insoluble gases such as hydrogen, or gases that do not dissolve easily in water, such as oxygen and carbon dioxide.

Gas Syringe The gas from the chemical reaction enters the gas syringe and pushes the plunger back. The gas syringe has a scale on it so you can measure the volume of gas given off in a certain time. Gas syringes are quite expensive though!

Gas TestingGas How do we test for its presence?Oxygen O2

Hydrogen H2

Carbon dioxide CO2

Physical ChangesPhysical changes can be changes of s _ _ _ _ or shape

Questions