NZASE Unit Standards: Level 1

Science Activity - Unit 20 Test version 1

Generic worksheet only

Unit Standard: 18986 version 2 - Select and use basic scientific equipment.

Element 1 Select and use basic scientific equipment.

Time allowed: No time limit. Covered throughout the year.

____________________________________________________________________TEACHER NOTES:

This standard required students to use a minimum of six pieces of scientific equipment correctly, accurately and in a safe and correct manner.

This standard can be assessed as part of a year's programme of work and especially when any practical work is being undertaken. Part of this could be assessed in conjunction with 21611, the experimental unit.

For moderation purposes the teacher needs to: record the task done when equipment is selected by students that

assesses against this standard. (1.1) keep a record of a students safe and correct usage. (1.2) Keep a record of student accuracy while using the equipment. (1.3) Be able to attest to the student's competence against this standard.

Evidence of this WILL be required by moderators.

Assessment schedule(NOTE teacher to add evidence for the chosen pieces of equipment)

Element. Evidence JudgementE 1 1.1 Student selects 6 items of

equipment appropriate to the taskEg: Measuring cylinder, test tube, conical flask, scales, balance, Spatula, petrie dish.

Must be achieved for 6 pieces of equipment.

E 1 1.2 Equipment operated in a safe and correct mannerEg: cleaning up spills, protective gear.

Must be achieved for a minimium of 6 pieces of equipment

E1 1.3 Equipment chosen was used accurately. Eg: accurate measurements, accurate recording.

Must be achieved for a minimium of 6 pieces of equipment

NZASE Unit Standards Level 1Science skills activity: Unit 21.This activity assesses: Unit Standard 18986 version 2. Select and use basic science equipment.

Antacid

Your stomach produces hydrochloric acid (HCl) to help digest food you have eaten. Sometimes there may be too much acid produced. This can cause “acid stomach” or indigestion.

Antacids are products sold to help people with indigestion. They work by neutralizing acid in the stomach.

The aim of this exercise is to measure how much antacid powder is needed to neutralize some hydrochloric acid. The acid is neutralizes when an indicator (methyl orange) changes from red to yellow.

Equipment needed250 mL flask 100 mL measuring cylinder methyl orange indicatorspatula petri dish balancesheet of white paper pH paper / pH meter

Method1. Place a spatula full of antacid powder into the petri dish.

2. Weigh the petri dish with the antacid powder. TEACHER CHECK. Record the mass.

3. Use a measuring cylinder to measure 50 mL of hydrochloric acid (HCl). TEACHER CHECK. Pour the HCl into a 250 mL flask.

4. Use pH paper/meter to estimate the pH of this solution. TEACHER CHECK. Record your result.

5. Add 4 drops of methyl orange indicator to the flask.

6. Place the flask on a sheet of white paper.

Be careful to ensure no antacid powder or acid is spilled during the next step.

7. Add a small amount of antacid powder to the flask. Gently swirl the flask to mix the contents. Repeat this until the colour in the flask changes from red to orange. This colour change shows the acid has been neutralized. TEACHER CHECK.

8. Weigh the petri dish with the remaining antacid powder. TEACHER CHECK. Record the mass.

9. Clean your work space and equipment and put equipment away tidily.

Results and calculation

Mass (g)A. Mass of petri dish and antacid at the

beginning : B. Mass of petri dish and antacid that did not

react : Mass of antacid used (A – B):

pH of acid solution = ____________

QuestionsWhat is the pH of the final mixture? ____________ How do you know?

If you had begun with 100 mL of hydrochloric acid (and not 50 mL), what mass of antacid powder would be needed to neutralize the acid?

Antacid (Unit Standard 18986) Assessment schedule and marking sheet

Method step Correct response

1.1

Ap

pro

pri

ate

eq

uip

me

nt

/

1.2

Sa

fe a

nd

co

rrec

t o

per

atio

n

1.3

Acc

ura

te

me

asu

rem

ent

/

1. Gets antacid sample

Selects spatula Selects petri dishSpatula used with antacid container near petri dish, no spillage or spillage cleaned up without delay

2. Use of balance

Selects balance Antacid in petri dish, balance zero checked and/or adjusted.Mass recorded accurately (+/- 2 of smallest scale of an analog scale)

3. Measuring cylinder

Selects measuring cylinder Selects correct acidMeasuring cylinder vertical, eye level, transfer to flask without spillageVolume is correct (+/- 2mL)

4.Measure pH

Selects pH paper/pH meterRecorded pH is +/- 1 unit of teacher’s measure

5. Adding indicator

Selects correct indicator.Uses transfer pipette/dropper No spillage or spillage cleaned upAppropriate amount

7.Neutralization

Spatula selected to transfer antacidSmall quantities antacid (eg ¼ total or less)No spillage of antacid powderFlask swirled to mix without spillage

8. Use of balance

Selects balance Antacid in petri dish, balance zero checked and/or adjusted.Mass recorded accurately (+/- 2 of smallest scale of an analog scale)

9.Clean up

Cleaning cloth used as appropriate, Equipment returned clean.

JudgementElement

6 1.1

6 1.2

6 1.3

Student name:

Teacher’s notes to “Antacid”

The intention with “antacid” is to provide an alternative to the generic assessment also provided for 18986. This type of assessment could be adapted for many “standard experiments” your class might normally do.

The activity could be included with Unit 6 (Chemical Reactions).

The task should be an individual activity, and students are observed using apparatus. Thus the numbers of students working at one time will need to be limited.

Student measurements are checked at various points. Teacher must measure pH of acid solution and record this for moderation purposes. (If 0.1 molL-1 HCl is used, pH = 1).

Use diluted acids (about 0.1 molL-1).

Students should be in a situation where they have to choose from alternative items of equipment (eg flask – beaker – test tube). Provide bottles of alternative acids (eg sulfuric acid, nitric acid) and alternative indicators (eg bromothymol blue). The student should be able to select the correct reagent.

The activity could also provide evidence for 21611 element 1.