Assessment Task

Prac 5.1A Molymod Kits

Use the molecular modelling kits to make models for:

• Elements, atoms, isotopes

• Mixtures, alloys

• Compounds, ions, bonds

• Chemical reactions

Practical 4.6B: Making Models

Molecular model kits

Task 5.4A  Alloys in Our World 

1.  Visit https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science-flexbook-2.0/section/5.11/primary/lesson/alloys-ms-ps and/or https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/8.12/primary/lesson/alloys-chem

2. Into your book:

• Write a definition of the term 'alloy' 

• Write a paragraph to describe what alloys are made of and how they are formed. 

• Draw a table and enter the components and uses of some common alloys (e.g. brass, bronze, stainless steel)

3. Complete the quizzes:

• https://flexbooks.ck12.org/assessment/ui/?test/view/practice/chemistry/Alloys-Practice&contextArtifactID=5271771&contextArtifactDescendantIdentifier=8.12&courseContextID=5271771&referrer=course_practice_widget&ep=https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/8.12/primary/lesson/alloys-chem?assessment=open 

4. Extra for interest: Read Metals with memories and/or Itching for beauty

Practical 5.4A: Making Steel Stronger https://www.riskassess.com.au/risk_assessment/9462703

Pearson 9 p21

Heating changes the physical properties of steel because it changes the size of its crystals.

Aim

To determine which treatment makes steel tougher.

Materials

• four steel hairpins

• steel wool

• Bunsen burner, bench mat and matches

• wooden peg

• beaker, tub or sink filled with cold water

• pliers (optional)

Procedure

1 Copy the table from the Results section into your workbook.

2 Count the number of times you can bend a hairpin before it snaps. One bend is out and in again. Enter the number in your table.

3 Hold another hairpin with the peg and heat the bend of the pin in a blue Bunsen burner flame until it is red-hot (Figure 1.2.7). Allow it to cool on the bench mat. This process is known as annealing.

1

SAFETY

The hairpin will get red-hot so use a peg at all times to hold it.

Water may spit when the hot pin is dropped into it so wear safety glasses at all times.

hairpin

blue ame

top of blue cone

quenching

cold water

tongs

4 Heat another hairpin in the same way, then cool it rapidly by dropping it into a beaker of water. This process is known as quenching.

5 Repeat step 4 with the remaining hairpin, then polish the bend with steel wool. Re-heat the bend of the pin, removing the pin occasionally to check whether the bend has gone blue. Once it has, remove the pin from the flame and allow it to cool on the mat. This process is known as tempering.

6 Bend each of the pins as before, counting the number of times you can bend the pin before it breaks. Record your counts in the results table.

Results

Record all your observations in a table like this one.

Treatment    Number of bends 

None

Annealing

Quenching

Tempering

Practical review

1 State which treatment caused your hairpin to become more:

a brittle (easier to snap)

b malleable (more ‘bendy’ and less likely to snap).

2 Fast cooling produces small crystals; slow cooling produces bigger ones. Predict which of the treatments

produced the biggest crystals.

3 Blacksmiths repeatedly heat, hammer and cool (quench) steel when making horseshoes. Propose a

reason.