Hygiene -HOW CLEAN ARE YOUR HANDS? (need to leave experiment over the
next 2 or 3 days and record observations).
Download file: Yr10 Diseases Hygiene and hand washing
- Hygiene-PART (A) -Hand Washing Experiment
- Watch the videos in PART (B) Hygiene Videos.
- Hygiene – Part (C) – Research – Different types of pathogens
- Hygiene – Part (D) – Research – Food Safety
- Hygiene- Part (D) – Research – Definitions
Practical work: Washing Hands
HYGIENE Part A Hand washing Experiment
Aim: To observe microbe numbers and types from unwashed and washed hands
Materials: Sterile nutrient agar plates, marking pen, sticky tape
Hand washing (water, soap bar, soap on tap, disinfectant, hand wipes, hand sanitiser, alcohol)
- Collect sterile agar plates (all poured with the same nutrient agar under the same conditions)
- Label each petri dish (write information on the base of the agar plate around the edge .
- Leave one plate unopened. Seal and label it = CONTROL
- For each plate use aseptic techniques to inoculate the plate:
- – clean bench with alcohol,
- bunsen burner running, work near bunsen flame,
- lifting the petri dish lid on angle only, agar facing downwards
- – to minimise the risk of contamination with microbes from the air)
5. Lightly press fingers onto agar side labelled unwashed, then wash hands with chosen technique
then press fingers onto labelled side washed
6. Seal petri dish with sticky tape (by winding the tape around the edge at the closure point)
and place in the storage tray (with the agar base side upwards
7. Incubate the plate at 300C for 48 hours (this decreases the risk of growing human pathogens)
8. Examine the plate (DO NOT OPEN)
9. Record the number and types of colonies visible through the petri dish lid
10. Collate class results on google drive (to ensure reliability through repetitions for a science experiment. (Due to cost involved, collating results from different groups may be feasible. If resources are available, you may have 5 sets of agar plates per group instead of one set of agar plate).
SAFETY RISK = potential spread of pathogenic organisms
1. Incubate at 300C only (not body temperature 370C to minimise chance of growing human pathogens).
2. Ensure plates fully sealed and never reopen (to stop exposure to potential pathogens).
3. Dispose of plates correctly at end of experiment (all plates placed in a pressure cooker and
exposed to heat and pressure to destroy all microbes before disposal)
Hand washing tested
|Bacterial colonies (estimation)||Fungal colonies (estimation)|
|Number of different types||Total number of colonies present||Number of different types||Total number of colonies present|
· Water only
· Soap bar
· Soap on tap
· Hand wipes
· Hand sanitiser
- Purpose: What do you want to learn?
- Hypothesis: What do you predict will happen?
3(a) List the controlled variables (Controlled variables are quantities that you as a scientist wants to remain constant so that the experiment can be considered as a fair test).
b) What is the independent variable? (The variable that is changed to allow comparisons).
c) What is the dependent variables? (The variables (things) that you as a scientist focus your
observation on to see how they respond to the changes made to the independent variables).
4. Was your hypothesis proved or disproved?___________________________________________________
5.Explain any differences in the bacterial cultures on the hand sanitizer and soap and water agar plates.
Which is a better method for cleaning your hands?
Better method: _____________________________________________________________________
6.From this experiment, what can you conclude about the effectiveness of hand-washing with soap and
water and using hand sanitizer to reduce the bacteria present on your hands?
7.How would you do this experiment differently if you carried it out again?
8.Discussion: Which hand washing method was the most successful? Research why this may be so (hint: look at hygiene control in hospitals) ____________________________________________________________
PART B HYGIENE Videos: (3 mins) Growing Bacteria https://www.youtube.com/watch?v=A0b6_kg2oMc
Keep Everything Clean (5 mins) https://www.youtube.com/watch?v=3FMZbIoPn2w
Spangler Science – Growing Bacteria cool science (5 mins) https://www.youtube.com/watch?v=LSZE6WofLAs
PART C HYGIENE – RESEARCH – Different types of PATHOGENS and how to interpret the colonies on the agar plate.
Use the website below to complete all the questions.
- Complete the table below:
|Characteristics used to identify the bacteria/fungi colonies||Meaning|
|Form||What is the basic shape of the colony? For example, circular, filamentous|
- Complete the table below:
|Types of pathogen||Pictures of colonies on agar plate||Description|
|Other types of pathogens|
Part (D) Hygiene- Research – Food Safety
- A rare burger might sound juicy and delicious. Should you eat it?
- Why should you wash the rock melon as soon as you get home and then store it in the fridge?
- You should not leave potato salad outside the fridge for more than 2 hours. Why?
Part (E) Research – Micro-organisms that can make you sick.
Germs live everywhere. You can find germs (microbes) in the air; on food, plants and animals; in soil and water — on just about every other surface, including your body.
Most germs won’t harm you. Your immune system protects you against infectious agents. However, some germs are formidable adversaries because they’re constantly mutating to breach your immune system’s defenses. Knowing how germs work can increase your chances of avoiding infection.
Infectious agents come in a variety of shapes and sizes. Categories include:
Write definitions for the above infectious agents.