Unit 3 Exam Revision

What is an Independant, dependant and control variable

IV= The thing you change

DV= The thing you measure

CV= The thing you keep the same

Example- “ Does the length of the rubber band affect the distance a paperclip travels when it is launched?”

What is the IV, DV and CV?

IV= length of rubber band

DV= distance the rubber band travelled

CV x2= age of rubber band and mass of paperclip

What is the formula for a hypothesis?

What is the formula for a null hypothesis?

Hypothesis= As the IV is changed (increase/decrease), then the DV is changed. This is because…

Null H= There is no significant difference between the IV and DV.

Hypothesis example- “A student is investigating how temp affects the rate of diffusion”.

Write a hypothesis for this statement

IV- temperature

DV- rate of diffusion

Hypothesis= As the temperature increases, the rate of diffusion also increases. This is because the particles have more kinetic energy.

Null hypothesis example- “A student is investigating how temp affects the rate of diffusion”.

Write a null hypothesis for this statement

There will be no significant difference between the temp and the rate of diffusion.

How to control control variables:

1. To control the volume..

2. To control pH..

3. To control temp..

4. To control light intensity..

5. To control concentration..

1. you would use a measuring cylinder

2. you would use a buffer

3. you would either use a thermostatically controlled water bath, air conditioned room or temp controlled greenhouse (depends on experiment)

4. you would use a bulb of known wattage at a known distance

5. you would use a measuring cylinder to measure a set vol of stock solution of known concentration. Then use another measuring cylinder to measure a known vol of water to dilute stock solution.

Equation for percentage error and uncertainty

Percentage error = uncertainty/measured value x100

Uncertainty= ½ of the graduation

Health and safety precautions- “Study how pH affects the activity of amylase on starch”

x3 Hazard, x3 Risk and x3 Precaution

Hazard 1 = Amylase, Risk 1= Allergic reaction, Precaution 1= Wear gloves, goggles

Hazard 2= Starch, Risk 2= Allergic reaction, Precaution 2= Wear gloves, goggles

Hazard 3= Broken glassware, Risk 3= Cuts, Precaution 3= Clean up as soon as possible using dust pan and brush and dispose into glassware bin.

What is Quantitative and Qualitative Data and give examples

Quantitative- Data in numerical form such as height of plant or number of leaves

Qualitative- Data not in numerical form such as colour of leaves and type of mineral ions

What is Continuous and Discrete data and give examples

Continuous data- numerical such as height of plant etc (can be shown as line graphs)

Discrete data- categories which cannot be split into smaller intervals on a scale such as number of people, leaves or amino acids

Interpreting your t-test results- “if the t value is less than the critical value?”

• The null hypothesis should be accepted

• Because the t value (number) is less than the critical value (number)

• Therefore, there is not a significant difference between the DV and IV

Interpreting your t-test results- “if the t value is more than the critical value?”

• The null hypothesis should be rejected

• Because the t value (number) is more than the critical value (number)

• Therefore, there is a significant difference between the DV and IV